US20110317528A1 - Thermally-assisted magnetic recording head including plasmon generator - Google Patents
Thermally-assisted magnetic recording head including plasmon generator Download PDFInfo
- Publication number
- US20110317528A1 US20110317528A1 US12/823,491 US82349110A US2011317528A1 US 20110317528 A1 US20110317528 A1 US 20110317528A1 US 82349110 A US82349110 A US 82349110A US 2011317528 A1 US2011317528 A1 US 2011317528A1
- Authority
- US
- United States
- Prior art keywords
- plasmon
- plasmon generator
- magnetic recording
- thermally
- light generating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
- G11B5/3109—Details
- G11B5/3116—Shaping of layers, poles or gaps for improving the form of the electrical signal transduced, e.g. for shielding, contour effect, equalizing, side flux fringing, cross talk reduction between heads or between heads and information tracks
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/56—Optics using evanescent waves, i.e. inhomogeneous waves
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/008—Surface plasmon devices
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
- G11B5/3109—Details
- G11B5/313—Disposition of layers
- G11B5/3133—Disposition of layers including layers not usually being a part of the electromagnetic transducer structure and providing additional features, e.g. for improving heat radiation, reduction of power dissipation, adaptations for measurement or indication of gap depth or other properties of the structure
- G11B5/314—Disposition of layers including layers not usually being a part of the electromagnetic transducer structure and providing additional features, e.g. for improving heat radiation, reduction of power dissipation, adaptations for measurement or indication of gap depth or other properties of the structure where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
- G11B5/3163—Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B5/60—Fluid-dynamic spacing of heads from record-carriers
- G11B5/6005—Specially adapted for spacing from a rotating disc using a fluid cushion
- G11B5/6088—Optical waveguide in or on flying head
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B2005/0002—Special dispositions or recording techniques
- G11B2005/0005—Arrangements, methods or circuits
- G11B2005/0021—Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
Definitions
- the present invention relates to a thermally-assisted magnetic recording head including a plasmon generator for use in thermally-assisted magnetic recording where a magnetic recording medium is irradiated with near-field light to lower the coercivity of the magnetic recording medium for data writing.
- the composite thin-film magnetic head has such a structure that a read head including a magnetoresistive element (hereinafter, also referred to as MR element) intended for reading and a write head including an induction-type electromagnetic transducer intended for writing are stacked on a substrate.
- MR element magnetoresistive element
- the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the magnetic recording medium.
- Magnetic recording media are discrete media each made of an aggregate of magnetic fine particles, each magnetic fine particle forming a single-domain structure.
- a single recording bit of a magnetic recording medium is composed of a plurality of magnetic fine particles.
- the magnetic fine particles must be made smaller.
- making the magnetic fine particles smaller causes the problem that the thermal stability of magnetization of the magnetic fine particles decreases with decreasing volume of the magnetic fine particles.
- it is effective to increase the anisotropic energy of the magnetic fine particles.
- increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the magnetic recording medium, and this makes it difficult to perform data writing with existing magnetic heads.
- thermally-assisted magnetic recording uses a magnetic recording medium having high coercivity.
- a magnetic field and heat are simultaneously applied to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing.
- a magnetic head for use in thermally-assisted magnetic recording will be referred to as a thermally-assisted magnetic recording head.
- near-field light is typically used as a means for applying heat to the magnetic recording medium.
- a commonly known method for generating near-field light is to use a near-field optical probe or so-called plasmon antenna, which is a piece of metal that generates near-field light from plasmons excited by irradiation with light.
- the plasmon antenna which generates near-field light by direct irradiation with light is known to exhibit very low efficiency of transformation of the applied light into near-field light.
- the energy of the light applied to the plasmon antenna is mostly reflected off the surface of the plasmon antenna, or transformed into thermal energy and absorbed by the plasmon antenna.
- the plasmon antenna is small in volume since the size of the plasmon antenna is set to be smaller than or equal to the wavelength of the light. The plasmon antenna therefore shows a significant increase in temperature when it absorbs the thermal energy.
- Such a temperature increase makes the plasmon antenna expand in volume and protrude from a medium facing surface, which is the surface of the thermally-assisted magnetic recording head to face the magnetic recording medium. This causes an end of the read head located in the medium facing surface to get farther from the magnetic recording medium, thereby causing the problem that a servo signal cannot be read during write operations.
- U.S. Patent Application Publication No. 2007/139818 A1 discloses a magnetic head in which a near-field light generating part, which generates near-field light when irradiated with laser light; and an end of a main magnetic pole layer are arranged to overlap each other directly or through a dielectric layer in the medium facing surface.
- U.S. Patent Application Publication No. 2009/168220 A1 discloses a magnetic head in which at least a part of a main magnetic pole is interposed between first and second near-field light generating parts, each of which generates near-field light when irradiated with laser light.
- the magnetic head disclosed in U.S. Patent Application Publication No. 2007/139818 A1 and the magnetic head disclosed in U.S. Patent Application Publication No. 2009/168220 A1 both make it possible to locate the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other, but neither can suppress a rise in temperature of the near-field light generating part since the near-field light generating part is directly irradiated with light.
- a thermally-assisted magnetic recording head employs such a configuration that the light propagated through the core is coupled with the plasmon generator in a surface plasmon mode through a buffer part, there arises the following problem if the position of occurrence of the write magnetic field and the position of occurrence of the near-field light are located close to each other. That is, in such a case, both the core and the magnetic pole need to be located near the plasmon generator. It follows that the magnetic pole is located near the core.
- the magnetic pole is typically made of a magnetic metal material. The presence of such a magnetic pole near the core causes the problem that part of the light propagated through the core is absorbed by the magnetic pole and the use efficiency of the light propagated through the core thereby decreases.
- a thermally-assisted magnetic recording head of the present invention includes: a medium facing surface that faces a magnetic recording medium; a magnetic pole that has an end face located in the medium facing surface and produces a write magnetic field for writing data on the magnetic recording medium; a waveguide including a core and a clad, the core propagating light; and a plasmon generator.
- the core has an evanescent light generating surface that generates evanescent light based on the light propagated through the core.
- the plasmon generator has an outer surface, the outer surface including: a plasmon exciting part that faces the evanescent light generating surface with a predetermined distance therebetween; and a front end face located in the medium facing surface.
- the plasmon generator has: a first sidewall part and a second sidewall part that are each connected to the plasmon exciting part, the first and second sidewall parts increasing in distance from each other with increasing distance from the plasmon exciting part; and at least one extended portion that is connected to an edge of at least one of the first and second sidewall parts, the edge being opposite from the plasmon exciting part. From the edge of the at least one of the first and second sidewall parts opposite from the plasmon exciting part, the at least one extended portion extends parallel to the evanescent light generating surface and away from both the first and second sidewall parts.
- the magnetic pole has a portion interposed between the first and second sidewall parts.
- the front end face includes: a first portion and a second portion that lie at respective ends of the first and second sidewall parts and are connected to each other into a V-shape; at least one third portion that lies at an end of the at least one extended portion; and a near-field light generating edge that lies at an end of the plasmon exciting part.
- the end face of the magnetic pole has a portion interposed between the first and second portions of the front end face.
- a surface plasmon is excited on the plasmon exciting part through coupling with the evanescent light generated from the evanescent light generating surface.
- the near-field light generating edge generates near-field light based on the surface plasmon excited on the plasmon exciting part.
- the at least one extended portion of the plasmon generator has a heat sink function of dissipating heat from the plasmon generator to outside.
- the magnetic pole may be in contact with the plasmon generator.
- the first and second sidewall parts may be connected to each other so that the connected first and second sidewall parts have a V-shaped cross section parallel to the medium facing surface.
- the plasmon exciting part may include a propagative edge that lies at an end of the connected first and second sidewall parts closer to the evanescent light generating surface.
- the near-field light generating edge may lie at an end of the propagative edge.
- the plasmon generator may further have a bottom part that is shaped like a plate and connects the first and second sidewall parts to each other at their respective edges closer to the evanescent light generating surface.
- the plasmon exciting part may include a flat surface part that is formed by a surface of the bottom part that is closer to the evanescent light generating surface.
- the flat surface part may include a width changing portion. The width changing portion may have a width that decreases with decreasing distance to the medium facing surface, the width being in a direction parallel to the medium facing surface and the evanescent light generating surface.
- the thermally-assisted magnetic recording head of the present invention may further include a buffer part that is located between the evanescent light generating surface and the plasmon exciting part and has a refractive index lower than that of the core.
- a dimension of the first and second sidewall parts in a direction perpendicular to the evanescent light generating surface may fall within a range of 200 to 400 nm.
- a dimension of the front end face on a virtual straight line that passes through the near-field light generating edge and extends in the direction perpendicular to the evanescent light generating surface may fall within a range of 20 to 70 nm.
- the thermally-assisted magnetic recording head of the present invention may further include a conductor made of a conductive material, the conductor having a Seebeck coefficient different from that of the plasmon generator and being in contact with the plasmon generator.
- a conductor made of a conductive material the conductor having a Seebeck coefficient different from that of the plasmon generator and being in contact with the plasmon generator.
- heat absorption by the Peltier effect occurs in a contact area between the plasmon generator and the conductor when a current is made to flow from one of the plasmon generator and the conductor, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area.
- the plasmon generator may be made of Au
- the conductive material may contain at least one of Co, Ni, and a CuNi alloy.
- the conductor may be in contact with the plasmon generator at least on a virtual straight line that passes through the near-field light generating edge and extends in the direction perpendicular to the evanescent light generating surface.
- a dimension of the conductor on the virtual straight line may fall within a range of 20 to 50 nm.
- At least part of the conductor may be interposed between the plasmon generator and the magnetic pole.
- the thermally-assisted magnetic recording head of the present invention may further include a first electrode that is electrically connected to the plasmon generator and a second electrode that is electrically connected to the conductor.
- a voltage for generating a current may be applied to the first and second electrodes.
- the conductor may be electrically connected to the magnetic pole, and a voltage for generating a current may be applied to the plasmon generator and the magnetic pole.
- a head gimbal assembly of the present invention includes: the thermally-assisted magnetic recording head of the present invention; and a suspension that supports the thermally-assisted magnetic recording head.
- a magnetic recording device of the present invention includes: a magnetic recording medium; the thermally-assisted magnetic recording head of the present invention; and a positioning device that supports the thermally-assisted magnetic recording head and positions the same with respect to the magnetic recording medium.
- a surface plasmon is excited on the plasmon exciting part of the plasmon generator through coupling with the evanescent light generated from the evanescent light generating surface of the core of the waveguide.
- the near-field light generating part generates near-field light based on the surface plasmon. According to the present invention, it is thereby possible to transform the light propagated through the core into near-field light with high efficiency.
- the front end face of the plasmon generator has the first and second portions that are connected to each other into a V-shape, and the near-field light generating edge lying at an end of the plasmon exciting part.
- the end face of the magnetic pole has the portion interposed between the first and second portions of the front end face. Consequently, according to the present invention, it is possible to locate the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other.
- the plasmon generator has at least one extended portion having the heat sink function as described above. Consequently, according to the present invention, it is possible to suppress a rise in temperature of the plasmon generator.
- the thermally-assisted magnetic recording head may include a conductor made of a conductive material, the conductor having a Seebeck coefficient different from that of the plasmon generator and being in contact with the plasmon generator. In such a case, it is possible to cool the plasmon generator by the Peltier effect and further suppress a rise in temperature of the plasmon generator.
- FIG. 1 is a perspective view showing a waveguide's core, a plasmon generator, and a magnetic pole of a thermally-assisted magnetic recording head according to a first embodiment of the invention.
- FIG. 2 is a front view showing a part of the medium facing surface of a head unit of the thermally-assisted magnetic recording head according to the first embodiment of the invention.
- FIG. 3 is a cross-sectional view showing the core, the plasmon generator, and the magnetic pole of the thermally-assisted magnetic recording head according to the first embodiment of the invention.
- FIG. 4 is a perspective view showing the main part of the heat unit of a magnetic recording device according to the first embodiment of the invention.
- FIG. 5 is a perspective view showing the magnetic recording device according to the first embodiment of the invention.
- FIG. 6 is a perspective view showing a head gimbal assembly according to the first embodiment of the invention.
- FIG. 7 is a perspective view showing the thermally-assisted magnetic recording head according to the first embodiment of the invention.
- FIG. 8 shows a cross section taken along line 8 - 8 of FIG. 7 .
- FIG. 9 is a plan view showing a part of the head unit of the thermally-assisted magnetic recording head according to the first embodiment of the invention.
- FIG. 10 is a block diagram showing the circuit configuration of the magnetic recording device according to the first embodiment of the invention.
- FIG. 11 is a cross-sectional view showing a step of a method of forming the plasmon generator and the magnetic pole of the first embodiment of the invention.
- FIG. 12 is a cross-sectional view showing a step that follows the step shown in FIG. 11 .
- FIG. 13 is a cross-sectional view showing a step that follows the step shown in FIG. 12 .
- FIG. 14 is a cross-sectional view showing a step that follows the step shown in FIG. 13 .
- FIG. 15 is a cross-sectional view showing a step that follows the step shown in FIG. 14 .
- FIG. 16 is a front view showing a core, a plasmon generator, and a magnetic pole in a medium facing surface of a model of a first type used in a second simulation.
- FIG. 17 is a front view showing a core, a plasmon generator, and a magnetic pole in a medium facing surface of a model of a second type used in the second simulation.
- FIG. 18 is a characteristic chart showing the effective write magnetic field determined by the second simulation.
- FIG. 19 is a characteristic chart showing the near-field light intensity determined by a third simulation.
- FIG. 20 is a perspective view showing a waveguide's core, a plasmon generator, and a magnetic pole of a thermally-assisted magnetic recording head according to a second embodiment of the invention.
- FIG. 21 is a plan view showing a plasmon exciting part of the plasmon generator shown in FIG. 20 .
- FIG. 22 is a front view showing a part of the medium facing surface of a head unit of a thermally-assisted magnetic recording head according to a third embodiment of the invention.
- FIG. 23 is a cross-sectional view showing a waveguide's core, a plasmon generator, and a magnetic pole of the thermally-assisted magnetic recording head according to the third embodiment of the invention.
- FIG. 24A and FIG. 24B are explanatory diagrams showing a step of a method of forming the plasmon generator, the magnetic pole, and the conductor of the third embodiment of the invention.
- FIG. 25A and FIG. 25B are explanatory diagrams showing a step that follows the step shown in FIG. 24A and FIG. 24B .
- FIG. 26A and FIG. 26B are explanatory diagrams showing a step that follows the step shown in FIG. 25A and FIG. 25B .
- FIG. 27 is a cross-sectional view showing a step that follows the step shown in FIG. 26A and FIG. 26B .
- FIG. 28 is a cross-sectional view showing a step that follows the step shown in FIG. 27 .
- FIG. 29 is a cross-sectional view showing a step that follows the step shown in FIG. 28 .
- FIG. 30 is a front view showing a part of the medium facing surface of a head unit of a thermally-assisted magnetic recording head according to a fourth embodiment of the invention.
- the magnetic disk drive includes a plurality of magnetic disks 201 as a plurality of magnetic recording media, and a spindle motor 202 for rotating the plurality of magnetic disks 201 .
- the magnetic disks 201 of the present embodiment are for use in perpendicular magnetic recording.
- the magnetic disks 201 each have such a structure that a soft magnetic backing layer, a middle layer, and a magnetic recording layer (perpendicular magnetization layer) are stacked in this order on a disk substrate.
- the magnetic disk drive further includes an assembly carriage device 210 having a plurality of driving arms 211 , and a plurality of head gimbal assemblies 212 attached to respective distal ends of the driving arms 211 .
- the head gimbal assemblies 212 each include a thermally-assisted magnetic recording head 1 according to the present embodiment, and a suspension 220 that supports the thermally-assisted magnetic recording head 1 .
- the assembly carriage device 210 is a device for positioning the thermally-assisted magnetic recording heads 1 on tracks that are formed in the magnetic recording layers of the magnetic disks 201 and that have recording bits aligned thereon.
- the assembly carriage device 210 further has a pivot bearing shaft 213 and a voice coil motor 214 .
- the plurality of driving arms 211 are stacked in a direction along the pivot bearing shaft 213 and are pivotable about the shaft 213 by being driven by the voice coil motor 214 .
- the magnetic recording device of the present invention is not structurally limited to the magnetic disk drive having the above-described configuration.
- the magnetic recording device of the present invention may be provided with a single magnetic disk 201 , a single driving arm 211 , a single head gimbal assembly 212 and a single thermally-assisted magnetic recording head 1 .
- the magnetic disk drive further includes a control circuit 230 that controls the read/write operations of the thermally-assisted magnetic recording heads 1 and also controls the light emitting operation of a laser diode serving as a light source for generating laser light for thermally-assisted magnetic recording described later.
- FIG. 6 is a perspective view showing the head gimbal assembly 212 of FIG. 5 .
- the head gimbal assembly 212 includes the thermally-assisted magnetic recording head 1 and the suspension 220 .
- the suspension 220 has a load beam 221 , a flexure 222 fixed to the load beam 221 and having flexibility, a base plate 223 provided at the base part of the load beam 221 , and a wiring member 224 provided on the load beam 221 and the flexure 222 .
- the wiring member 224 includes a plurality of leads.
- the thermally-assisted magnetic recording head 1 is fixed to the flexture 222 at the distal end of the suspension 220 such that the head 1 faces the surface of the magnetic disk 201 with a predetermined spacing (flying height).
- One end of the wiring member 224 is electrically connected to a plurality of terminals of the thermally-assisted magnetic recording head 1 .
- the other end of the wiring member 224 is provided with a plurality of pad-shaped terminals arranged at the base part of the load beam 221 .
- the assembly carriage device 210 and the suspension 220 correspond to the positioning device of the present invention.
- the head gimbal assembly of the present invention is not limited to the one having the configuration shown in FIG. 6 .
- the head gimbal assembly of the present invention may have an IC chip for driving the head that is mounted somewhere along the suspension 220 .
- FIG. 7 is a perspective view showing the thermally-assisted magnetic recording head 1 .
- FIG. 8 shows a cross section taken along line 8 - 8 of FIG. 7 .
- FIG. 9 is a plan view showing a part of a head unit of the thermally-assisted magnetic recording head.
- the thermally-assisted magnetic recording head 1 includes a slider 10 and a light source unit 50 .
- FIG. 8 shows the state where the slider 10 and the light source unit 50 are separated from each other.
- the slider 10 includes a slider substrate 11 and a head unit 12 .
- the slider substrate 11 is rectangular-solid-shaped and is made of a ceramic material such as aluminum oxide-titanium carbide (Al 2 O 3 —TiC)
- the slider substrate 11 has a medium facing surface 11 a that faces the magnetic disk 201 , a rear surface 11 b on the opposite side from the medium facing surface 11 a , and four surfaces that connect the medium facing surface 11 a to the rear surface 11 b .
- One of the four surfaces that connect the medium facing surface 11 a to the rear surface 11 b is an element-forming surface 11 c .
- the element-forming surface 11 c is perpendicular to the medium facing surface 11 a .
- the head unit 12 is disposed on the element-forming surface 11 c .
- the medium facing surface 11 a is processed so as to obtain an appropriate flying height of the slider 10 with respect to the magnetic disk 201 .
- the head unit 12 has a medium facing surface 12 a that faces the magnetic disk 201 , and a rear surface 12 b on the opposite side from the medium facing surface 12 a .
- the medium facing surface 12 a is parallel to the medium facing surface 11 a of the slider substrate 11 .
- a position located in a direction that extends perpendicular to the element-forming surface 11 c and away from the element-forming surface 11 c is defined as “above”, and a position located in a direction opposite to the above-mentioned direction is defined as “below”.
- the surface closer to the element-forming surface 11 c is defined as a “bottom surface,” and the surface farther from the element-forming surface 11 c as a “top surface.”
- X direction, Y direction, Z direction, ⁇ X direction, ⁇ Y direction, and ⁇ Z direction will be defined as follows.
- the X direction is a direction perpendicular to the medium facing surface 11 a and from the medium facing surface 11 a to the rear surface lib.
- the Y direction is a direction parallel to the medium facing surface 11 a and the element-forming surface 11 c and from the back side to the front side of FIG. 8 .
- the Z direction is a direction that extends perpendicular to the element-forming surface 11 c and away from the element-forming surface 11 c .
- the ⁇ X direction, the ⁇ Y direction, and the ⁇ Z direction are opposite to the X direction, the Y direction, and the Z direction, respectively.
- the magnetic disk 201 moves in the Z direction.
- the slider 10 has an air inflow end (a leading end) at the end of the medium facing surface 11 a in the ⁇ Z direction.
- the slider 10 has an air outflow end (a trailing end) at the end of the medium facing surface 12 a in the Z direction.
- Track width direction TW is a direction parallel to the Y direction.
- the light source unit 50 includes a laser diode 60 serving as a light source for emitting laser light, and a support member 51 that is shaped like a rectangular solid and supports the laser diode 60 .
- the support member 51 is made of, for example, a ceramic material such as aluminum oxide-titanium carbide (Al 2 O 3 —TiC).
- the support member 51 has a bonding surface 51 a , a rear surface 51 b on the opposite side from the bonding surface 51 a , and four surfaces that connect the bonding surface 51 a to the rear surface 51 b .
- One of the four surfaces that connect the bonding surface 51 a to the rear surface 51 b is a light-source-mounting surface 51 c .
- the bonding surface 51 a is the surface to be bonded to the rear surface 11 b of the slider substrate 11 .
- the light-source-mounting surface 51 c is perpendicular to the bonding surface 51 a and parallel to the element-forming surface 11 c .
- the laser diode 60 is mounted on the light-source-mounting surface 51 c .
- the support member 51 may have a heat sink function of dissipating heat generated by the laser diode 60 , in addition to the function of supporting the laser diode 60 .
- the head unit 12 includes an insulating layer 13 disposed on the element-forming surface 11 c , and also includes a read head 14 , a write head 16 , and a protection layer 17 that are stacked in this order on the insulating layer 13 .
- the insulating layer 13 and the protection layer 17 are each made of an insulating material such as Al 2 O 3 (hereinafter, also referred to as alumina).
- the read head 14 includes: a bottom shield layer 21 disposed on the insulating layer 13 ; an MR element 22 disposed on the bottom shield layer 21 ; a top shield layer 23 disposed on the MR element 22 ; and an insulating layer 24 disposed between the bottom shield layer 21 and the top shield layer 23 around the MR element 22 .
- the bottom shield layer 21 and the top shield layer 23 are each made of a soft magnetic material.
- the insulating layer 24 is made of an insulating material such as alumina.
- the MR element 22 may be a giant magnetoresistive (GMR) element or a tunneling magnetoresistive (TMR) element, for example.
- the GMR element may be of either the current-in-plane (CIP) type in which a sense current for use in magnetic signal detection is fed in a direction nearly parallel to the plane of layers constituting the GMR element or the current-perpendicular-to-plane (CPP) type in which the sense current is fed in a direction nearly perpendicular to the plane of layers constituting the GMR element.
- CIP current-in-plane
- CPP current-perpendicular-to-plane
- the bottom shield layer 21 and the top shield layer 23 may also function as electrodes for feeding the sense current to the MR element 22 .
- the MR element 22 is a CIP-type GMR element, insulating films are respectively provided between the MR element 22 and the bottom shield layer 21 and between the MR element 22 and the top shield layer 23 , and two leads are provided between these insulating films in order to feed the sense current to the MR element 22 .
- the head unit 12 further includes an insulating layer 25 disposed on the top shield layer 23 , a middle shield layer 26 disposed on the insulating layer 25 , and an insulating layer 27 disposed on the middle shield layer 26 .
- the middle shield layer 26 has the function of shielding the MR element 22 from a magnetic field produced in the write head 16 .
- the insulating layers 25 and 27 are each made of an insulating material such as alumina.
- the middle shield layer 26 is made of a soft magnetic material.
- the insulating layer 25 and the middle shield layer 26 may be omitted.
- the write head 16 of the present embodiment is for use in perpendicular magnetic recording.
- the write head 16 includes a bottom yoke layer 28 disposed on the insulating layer 27 , a bottom shield layer 29 disposed on the bottom yoke layer 28 in the vicinity of the medium facing surface 12 a , a coupling layer 42 A disposed on the bottom yoke layer 28 at a position away from the medium facing surface 12 a , and an insulating layer 30 disposed around the bottom yoke layer 28 , the bottom shield layer 29 and the coupling layer 42 A.
- the bottom yoke layer 28 , the bottom shield layer 29 , and the coupling layer 42 A are each made of a soft magnetic material.
- the insulating layer 30 is made of an insulating material such as alumina.
- the write head 16 further includes a waveguide that includes a core 32 and a clad.
- the clad includes a clad layer 31 and a clad layer 33 .
- the clad layer 31 is disposed over the bottom shield layer 29 , the insulating layer 30 and the coupling layer 42 A.
- the core 32 is disposed on the clad layer 31 .
- the clad layer 33 covers the clad layer 31 and the core 32 .
- the core 32 extends in a direction perpendicular to the medium facing surface 12 a (X direction).
- the core 32 has an incident end 32 a , an end face closer to the medium facing surface 12 a , a top surface, a bottom surface, and two side surfaces.
- the end face of the core 32 may be located in the medium facing surface 12 a or away from the medium facing surface 12 a .
- FIG. 8 shows an example where the end face of the core 32 is located in the medium facing surface 12 a .
- the core 32 propagates laser light that is emitted from the laser diode 60 and incident on the incident end 32 a.
- the core 32 is made of a dielectric material that transmits the laser light.
- Each of the clad layers 31 and 33 is made of a dielectric material and has a refractive index lower than that of the core 32 .
- the write head 16 further includes a plasmon generator 34 disposed above the core 32 in the vicinity of the medium facing surface 12 a , and a magnetic pole 35 disposed at such a position that the plasmon generator 34 is interposed between the magnetic pole 35 and the core 32 .
- the magnetic pole 35 has a top surface that is located at a level higher than the top surface of the clad layer 33 .
- the plasmon generator 34 is made of a conductive material such as metal.
- the plasmon generator 34 may be made of one element selected from the group consisting of Pd, Pt, Rh, Ir, Ru, Au, Ag, Cu, and Al, or of an alloy composed of two or more of these elements.
- the magnetic pole 35 is made of a soft magnetic material, or a magnetic metal material in particular.
- FIG. 9 shows an example of the length of the magnetic pole 35 in the X direction.
- the magnetic pole 35 has a length of 3 ⁇ m in the X direction.
- the shapes and locations of the core 32 , the plasmon generator 34 and the magnetic pole 35 will be detailed later.
- the write head 16 further includes a coupling layer 42 C at a position away from the medium facing surface 12 a .
- a part of the coupling layer 42 C is embedded in the clad layer 33 .
- the coupling layer 42 C is located above the coupling layer 42 A.
- the coupling layer 42 C has a top surface at a level higher than the top surface of the clad layer 33 .
- the coupling layer 42 C is made of a soft magnetic material.
- the write head 16 further includes two coupling portions 42 B 1 and 42 B 2 embedded in the clad layers 31 and 33 .
- the coupling portions 42 B 1 and 42 B 2 are each made of a soft magnetic material.
- the coupling portions 42 B 1 and 42 B 2 are located on opposite sides of the core 32 in the track width direction TW, each at a distance from the core 32 .
- the bottom surfaces of the coupling portions 42 B 1 and 42 B 2 are in contact with the top surface of the coupling layer 42 A.
- the top surfaces of the coupling portions 42 B 1 and 42 B 2 are in contact with the bottom surface of the coupling layer 42 C.
- the write head 16 further includes an insulating layer 37 disposed around the magnetic pole 35 and the coupling layer 42 C on the clad layer 33 , an insulating layer 38 disposed on the insulating layer 37 , a coupling layer 36 disposed on the magnetic pole 35 , and a coupling layer 42 D disposed on the coupling layer 42 C.
- the coupling layer 36 has an end face that is closer to the medium facing surface 12 a , the end face being located at a distance from the medium facing surface 12 a.
- the write head 16 further includes a plurality of first coil elements 40 A disposed on the insulating layer 38 , and an insulating layer 39 disposed around the coupling layers 36 and 42 D and the first coil elements 40 A.
- the first coil elements 40 A are arranged to align in the X direction.
- the first coil elements 40 A each have a main part that extends in the track width direction TW (Y direction).
- the first coil elements 40 A are each made of a conductive material such as copper.
- the coupling layers 36 and 42 D are each made of a soft magnetic material.
- the insulating layers 37 , 38 , and 39 are each made of an insulating material such as alumina.
- the write head 16 further includes an insulating layer 41 disposed to cover the first coil elements 40 A, a top yoke layer 43 disposed over the coupling layers 36 and 42 D and the insulating layer 41 , and an insulating layer 44 disposed around the top yoke layer 43 .
- the top yoke layer 43 is in contact with the top surface of the coupling layer 36 at a position near the medium facing surface 12 a , and in contact with the top surface of the coupling layer 42 D at a position away from the medium facing surface 12 a .
- FIG. 9 shows an example of the dimensions of the top yoke layer 43 in the X direction and in the track width direction TW (Y direction).
- the top yoke layer 43 has a dimension of 12 ⁇ m in the X direction and a dimension of 17 ⁇ m in the track width direction TW (Y direction).
- the top yoke layer 43 is made of a soft magnetic material.
- the insulating layers 41 and 44 are each made of an insulating material such as alumina.
- the write head 16 further includes an insulating layer 45 disposed over the top yoke layer 43 and the insulating layer 44 , and a plurality of second coil elements 40 B disposed on the insulating layer 45 .
- the insulating layer 45 is made of an insulating material such as alumina.
- FIG. 9 shows the second coil elements 40 B.
- the second coil elements 40 B are arranged to align in the X direction.
- the second coil elements 40 B each have a main part that extends in the track width direction TW (Y direction).
- the second coil elements 40 B are each made of a conductive material such as copper.
- the thermally-assisted magnetic recording head 1 further includes a plurality of connecting portions.
- the plurality of connecting portions connect the plurality of first coil elements 40 A to the plurality of second coil elements 40 B so as to form a coil 40 wound around the top yoke layer 43 helically.
- the plurality of connecting portions are provided to penetrate the insulating layers 41 , 44 , and 45 .
- the connecting portions are each made of a conductive material such as copper.
- the bottom shield layer 29 , the bottom yoke layer 28 , the coupling layer 42 A, the coupling portions 42 B 1 and 42 B 2 , the coupling layers 42 C and 42 D, the top yoke layer 43 , the coupling layer 36 , and the magnetic pole 35 form a magnetic path for passing a magnetic flux corresponding to the magnetic field produced by the coil 40 .
- the magnetic pole 35 has an end face located in the medium facing surface 12 a , allows the magnetic flux corresponding to the magnetic field produced by the coil 40 to pass, and produces a write magnetic field for writing data on the magnetic disk 201 by means of the perpendicular magnetic recording system.
- the bottom shield layer 29 takes in a magnetic flux that is generated from the end face of the magnetic pole 35 and that expands in directions other than the direction perpendicular to the plane of the magnetic disk 201 , and thereby prevents the magnetic flux from reaching the magnetic disk 201 .
- the protection layer 17 is disposed to cover the write head 16 .
- the head unit 12 further includes a pair of terminals 18 that are disposed on the top surface of the protection layer 17 and electrically connected to the MR element 22 , and another pair of terminals 19 that are disposed on the top surface of the protection layer 17 and electrically connected to the coil 40 .
- These terminals 18 and 19 are electrically connected to the plurality of pad-shaped terminals of the wiring member 224 shown in FIG. 6 .
- the laser diode 60 may be a laser diode of InP type, GaAs type, GaN type or the like that is commonly used for such applications as communications, optical disc storage and material analysis.
- the laser diode 60 may emit laser light of any wavelength within the range of, for example, 375 nm to 1.7 ⁇ m.
- the laser diode 60 may be an InGaAsP/InP quarternary mixed crystal laser diode having an emittable wavelength range of 1.2 to 1.67 ⁇ m, for example.
- the laser diode 60 has a multilayer structure including a lower electrode 61 , an active layer 62 , and an upper electrode 63 .
- a reflecting layer 64 made of, for example, SiO 2 or Al 2 O 3 , is formed on two cleavage planes of the multilayer structure so as to excite oscillation by total reflection of light.
- the reflecting layer 64 has an opening for emitting laser light in the position of the active layer 62 including an emission center 62 a .
- the laser diode 60 has a thickness T LA of around 60 to 200 ⁇ m, for example.
- the light source unit 50 further includes a terminal 52 disposed on the light-source-mounting surface 51 c and electrically connected to the lower electrode 61 , and a terminal 53 disposed on the light-source-mounting surface 51 c and electrically connected to the upper electrode 63 . These terminals 52 and 53 are electrically connected to the plurality of pad-shaped terminals of the wiring member 224 shown in FIG. 6 .
- a predetermined voltage is applied to the laser diode 60 through the terminals 52 and 53 , laser light is emitted from the emission center 62 a of the laser diode 60 .
- the laser light to be emitted from the laser diode 60 is preferably TM-mode polarized light whose electric field oscillates in a direction perpendicular to the plane of the active layer 62 .
- the laser diode 60 can be driven by a power supply inside the magnetic disk drive.
- the magnetic disk drive usually includes a power supply that generates a voltage of 2 V or so, for example. This supply voltage is sufficient to drive the laser diode 60 .
- the laser diode 60 has a power consumption of, for example, several tens of milliwatts or so, which can be adequately covered by the power supply in the magnetic disk drive.
- the light source unit 50 is fixed to the slider 10 by bonding the bonding surface 51 a of the support member 51 to the rear surface 11 b of the slider substrate 11 , as shown in FIG. 8 .
- the laser diode 60 and the core 32 are positioned so that the laser light emitted from the laser diode 60 will be incident on the incident end 32 a of the core 32 .
- FIG. 1 is a perspective view showing the core 32 , the plasmon generator 34 , and the magnetic pole 35 .
- FIG. 2 is a front view showing a part of the medium facing surface 12 a of the head unit 12 .
- FIG. 3 is a cross-sectional view showing the core 32 , the plasmon generator 34 , and the magnetic pole 35 .
- FIG. 4 is a perspective view showing the main part of the heat unit 12 . Note that FIG. 1 illustrates an exploded view of the plasmon generator 34 and the magnetic pole 35 .
- the core 32 further has: an end face 32 b that is closer to the medium facing surface 12 a ; an evanescent light generating surface 32 c , which is a top surface; a bottom surface 32 d ; and two side surfaces 32 e and 32 f , as shown in FIG. 1 .
- the evanescent light generating surface 32 c generates evanescent light based on the light propagated through the core 32 . While FIG. 1 to FIG. 3 show an example where the end face 32 b is located in the medium facing surface 12 a , the end face 32 b may be located away from the medium facing surface 12 a.
- the clad layer 33 has a top surface 33 a located above the core 32 , and a groove 33 b that opens in the top surface 33 a and is located above the core 32 .
- the groove 33 b extends in the direction perpendicular to the medium facing surface 12 a (X direction).
- the groove 33 b is V-shaped in cross section parallel to the medium facing surface 12 a.
- the plasmon generator 34 has an outer surface that includes a plasmon exciting part 341 and a front end face 342 .
- the plasmon exciting part 341 faces the evanescent light generating surface 32 c of the core 32 with a predetermined distance therebetween.
- the front end face 342 is located in the medium facing surface 12 a . Surface plasmons are excited on the plasmon exciting part 341 through coupling with the evanescent light generated from the evanescent light generating surface 32 c . As shown in FIG.
- the clad layer 33 has a part interposed between the evanescent light generating surface 32 c and the plasmon exciting part 341 , the part of the clad layer 33 forming a buffer part 33 A that has a refractive index lower than that of the core 32 .
- the plasmon generator 34 has a V-shaped portion 34 A that has an end face located in the medium facing surface 12 a .
- the V-shaped portion 34 A extends in the direction perpendicular to the medium facing surface 12 a (X direction).
- the groove 33 b mentioned above is to accommodate the V-shaped portion 34 A.
- the V-shaped portion 34 A has a first sidewall part 34 A 1 and a second sidewall part 34 A 2 that are each connected to the plasmon exciting part 341 , and that increase in distance from each other with increasing distance from the plasmon exciting part 341 .
- the first and second sidewall parts 34 A 1 and 34 A 2 are each shaped like a plate.
- the first and second sidewall parts 34 A 1 and 34 A 2 are connected to each other so that the connected first and second sidewall parts 34 A 1 and 34 A 2 have a V-shaped cross section parallel to the medium facing surface 12 a.
- the plasmon generator 34 further has at least one extended portion that is connected to an edge of at least one of the first and second sidewall parts 34 A 1 and 34 A 2 , the edge being opposite from the plasmon exciting part 341 .
- the plasmon generator 34 has an extended portion 34 B that is connected to the edge of the first sidewall part 34 A 1 opposite from the plasmon exciting part 341 , and an extended portion 34 C that is connected to the edge of the second sidewall part 34 A 2 opposite from the plasmon exciting part 341 .
- the extended portion 34 B extends parallel to the evanescent light generating surface 32 c and away from both the first and second sidewall parts 34 A 1 and 34 A 2 ( ⁇ Y direction).
- the extended portion 34 C extends parallel to the evanescent light generating surface 32 c and away from both the first and second sidewall parts 34 A 1 and 34 A 2 (Y direction).
- the outer edges of the extended portions 34 B and 34 C lie outside the outer edges of the magnetic pole 35 .
- the plasmon exciting part 341 has a propagative edge 341 a that lies at an end of the connected first and second sidewall parts 34 A 1 and 34 A 2 closer to the evanescent light generating surface 32 c .
- the entire plasmon exciting part 341 is composed of the propagative edge 341 a .
- the propagative edge 341 a propagates plasmons.
- the propagative edge 341 a may have the shape of a perfectly pointed edge whereas it may have an arc shape in a microscopic view.
- the front end face 342 has a first portion 342 a and a second portion 342 b that lie at respective ends of the first and second sidewall parts 34 A 1 and 34 A 2 and are connected to each other into a V-shape, a third portion 342 c that lies at an end of the extended portion 34 B, a fourth portion 342 d that lies at an end of the extended portion 34 C, and a near-field light generating edge 342 e that lies at an end of the plasmon exciting part 341 (propagative edge 341 a ).
- the near-field light generating edge 342 e generates near-field light based on the surface plasmons excited on the plasmon exciting part 341 .
- the near-field light generating edge 342 e may have the shape of a perfectly pointed edge whereas it may have an arc shape in a microscopic view.
- the magnetic pole 35 has a first portion 35 A and a second portion 35 B.
- the first portion 35 A is accommodated in the space formed by the V-shaped portion 34 A (the first and second sidewall parts 34 A 1 and 34 A 2 ) of the plasmon generator 34 .
- the second portion 35 B is located farther from the evanescent light generating surface 32 c of the core 32 than is the first portion 35 A.
- the border between the first portion 35 A and the second portion 35 B is shown by a chain double-dashed line.
- the first portion 35 A is triangular-prism-shaped.
- the first portion 35 A is interposed between the first and second sidewall parts 34 A 1 and 34 A 2 of the V-shaped portion 34 A of the plasmon generator 34 , and is in contact with the first and second sidewall parts 34 A 1 and 34 A 2 .
- the first portion 35 A has a constant width in a direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) regardless of the distance from the medium facing surface 12 a.
- the second portion 35 B has a front part 35 B 1 and a rear part 35 B 2 .
- the front part 35 B 1 has an end face located in the medium facing surface 12 a .
- the rear part 35 B 2 is connected to an end of the front part 35 B 1 opposite from the medium facing surface 12 a .
- the front part 35 B 1 has a constant width in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) regardless of the distance from the medium facing surface 12 a , the width being greater than that of the first portion 35 A.
- the width of the rear part 35 B 2 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) is equal to that of the front part 35 B 1 at the border with the front part 35 B 1 , and increases with increasing distance from the medium facing surface 12 a.
- the magnetic pole 35 has an end face 351 located in the medium facing surface 12 a .
- the end face 351 includes a first portion 351 a and a second portion 351 b .
- the first portion 351 a is the end face of the first portion 35 A.
- the second portion 351 b is the end face of the second portion 35 B.
- the second portion 351 b is also the end face of the front part 35 B 1 .
- the first portion 351 a has a triangular shape and is interposed between the first and second portions 342 a and 342 b of the front end face 342 of the plasmon generator 34 .
- the first portion 351 a has a tip 351 c located at its bottom end.
- the width of the core 32 in the track width direction TW (Y direction) in the vicinity of the plasmon generator 34 will be represented by the symbol W WG .
- the thickness (dimension in the Z direction) of the core 32 in the vicinity of the plasmon generator 34 will be represented by the symbol T WG .
- W WG falls within the range of 0.3 to 100 ⁇ m for example.
- T WG falls within the range of 0.1 to 4 ⁇ m, for example.
- the core 32 excluding the part in the vicinity of the plasmon generator 34 may have a width greater than W WG .
- the core 32 excluding the part in the vicinity of the plasmon generator 34 has a width of 4 ⁇ m.
- the dimension of the first and second portions 342 a and 342 b of the front end face 342 of the plasmon generator 34 in the track width direction TW (Y direction) will be represented by the symbol W PGA .
- the dimension of the first and second portions 342 a and 342 b in the Z direction will be represented by the symbol T PG .
- Both W PGA and T PG are sufficiently smaller than the wavelength of the laser light to be propagated through the core 32 .
- the dimension of the first and second sidewall parts 34 A 1 and 34 A 2 in a direction perpendicular to the evanescent light generating surface 32 c (Z direction) is equal to T PG .
- T PG preferably falls within the range of 200 to 400 nm. The reason will be detailed later.
- the widths of the third portion 342 c and the fourth portion 342 d of the front end face 342 of the plasmon generator 34 in the track width direction TW (Y direction) will be represented by the symbols W PGB and W PGC , respectively.
- W PGB and W PGC are equal.
- W PGB and W PGC fall within the range of 0.5 to 20 ⁇ m, for example.
- the extended portions 34 B and 34 C are depicted as having a width greater than W PGB and W PGC in positions away from the medium facing surface 12 a .
- the extended portions 34 B and 34 C may each have a constant width regardless of the distance from the medium facing surface 12 a.
- the length of the plasmon generator 34 in the X direction will be represented by the symbol H PG .
- H PG falls within the range of 0.6 to 4.0 ⁇ m, for example.
- the X-direction length of a portion of the plasmon exciting part 341 of the plasmon generator 34 , the portion being opposed to the evanescent light generating surface 32 c will be represented by the symbol H BF .
- the distance between the plasmon exciting part 341 and the evanescent light generating surface 32 c will be represented by the symbol T BF .
- Both H BF and T BF are important parameters in achieving appropriate excitation and propagation of surface plasmons.
- H BF preferably falls within the range of 0.6 to 4.0 ⁇ m, and is preferably greater than the wavelength of the laser light to be propagated through the core 32 .
- the end face 32 b of the core 32 is located in the medium facing surface 12 a , so that H BF is equal to H PG .
- T BF preferably falls within the range of 10 to 100 nm.
- the distance between the near-field light generating edge 342 e of the front end face 342 of the plasmon generator 34 and the end face 32 b of the core 32 is equal to T BF .
- the distance between the near-field light generating edge 342 e of the front end face 342 of the plasmon generator 34 and the tip 351 c of the first portion 351 a of the end face 351 of the magnetic pole 35 will be represented by the symbol D 1 .
- the dimension of the front end face 342 on a virtual straight line L is equal to D 1 , the virtual straight line L passing through the near-field light generating edge 342 e and extending in the direction perpendicular to the evanescent light generating surface 32 c .
- D 1 preferably falls within the range of 20 to 70 nm. The reason will be detailed later.
- H PD falls within the range of 0.3 to 1.0 ⁇ m, for example.
- Laser light 46 emitted from the laser diode 60 is propagated through the core 32 of the waveguide to reach the vicinity of the plasmon generator 34 .
- the laser light 46 is totally reflected at the evanescent light generating surface 32 c which is the interface between the core 32 and the buffer part 33 A. This generates evanescent light 47 permeating into the buffer part 33 A.
- the evanescent light 47 and fluctuations of charges on the plasmon exciting part 341 (propagative edge 341 a ) of the outer surface of the plasmon generator 34 are coupled with each other to induce a surface plasmon polariton mode.
- surface plasmons are excited on the plasmon exciting part 341 (propagative edge 341 a ) through coupling with the evanescent light 47 generated from the evanescent light generating surface 32 c.
- the surface plasmons excited on the plasmon exciting part 341 (propagative edge 341 a ) of the outer surface of the plasmon generator 34 are transformed into edge plasmons to propagate along the propagative edge 341 a to the near-field light generating edge 342 e . Consequently, the edge plasmons concentrate at the near-field light generating edge 342 e , and near-field light 48 occurs from the near-field light generating edge 342 e based on the edge plasmons.
- the near-field light 48 is projected toward the magnetic disk 201 , reaches the surface of the magnetic disk 201 , and heats a part of the magnetic recording layer of the magnetic disk 201 . This lowers the coercivity of the part of the magnetic recording layer. In thermally-assisted magnetic recording, the part of the magnetic recording layer with the lowered coercivity is subjected to a write magnetic field produced by the magnetic pole 35 for data writing.
- the control circuit 230 includes a control LSI (large scale integrated circuit) 100 , a ROM (read only memory) 101 connected to the control LSI 100 , a write gate 111 connected to the control LSI 100 , and a write circuit 112 connected to the write gate 111 and the coil 40 .
- control LSI large scale integrated circuit
- ROM read only memory
- the control circuit 230 further includes a constant current circuit 121 connected to the MR element 22 and the control LSI 100 , an amplifier 122 connected to the MR element 22 , and a demodulator circuit 123 connected to an output of the amplifier 122 and the control LSI 100 .
- the control circuit 230 further includes a laser control circuit 131 connected to the laser diode 60 and the control LSI 100 , and a temperature detector 132 connected to the control LSI 100 .
- the control LSI 100 supplies write data and a write control signal to the write gate 111 .
- the control LSI 100 supplies a read control signal to the constant current circuit 121 and the demodulator circuit 123 , and receives read data output from the demodulator circuit 123 .
- the control LSI 100 supplies a laser ON/OFF signal and an operating current control signal to the laser control circuit 131 .
- the temperature detector 132 detects the temperature of the magnetic recording layer of the magnetic disk 201 , and supplies this temperature information to the control LSI 100 .
- the ROM 101 contains a control table and the like for controlling the value of the operating current to be supplied to the laser diode 60 .
- the control LSI 100 supplies write data to the write gate 111 .
- the write gate 111 supplies the write data to the write circuit 112 only when the write control signal indicates a write operation.
- the write circuit 112 passes a write current through the coil 40 . Consequently, the magnetic pole 35 produces a write magnetic field and data is written on the magnetic recording layer of the magnetic disk 201 through the use of the write magnetic field.
- the constant current circuit 121 supplies a certain sense current to the MR element 22 only when the read control signal indicates a read operation.
- the output voltage of the MR element 22 is amplified by the amplifier 122 and input to the demodulator circuit 123 .
- the demodulator circuit 123 demodulates the output of the amplifier 122 to generate read data, and supplies the read data to the control LSI 100 .
- the laser control circuit 131 controls the supply of the operating current to the laser diode 60 on the basis of the laser ON/OFF signal, and also controls the value of the operating current to be supplied to the laser diode 60 on the basis of the operating current control signal.
- the laser ON/OFF signal indicates an ON operation
- the laser control circuit 131 exercises control so that an operating current at or above an oscillation threshold is supplied to the laser diode 60 . Consequently, the laser diode 60 emits laser light, and the laser light is propagated through the core 32 .
- the near-field light 48 occurs from the near-field light generating edge 342 e of the plasmon generator 34 .
- the near-field light 48 heats a part of the magnetic recording layer of the magnetic disk 201 , thereby lowering the coercivity of that part.
- the part of the magnetic recording layer with the lowered coercivity is subjected to the write magnetic field produced by the magnetic pole 35 for performing data writing.
- the control LSI 100 consults the control table stored in the ROM 101 to determine the value of the operating current of the laser diode 60 . Using the operating current control signal, the control LSI 100 controls the laser control circuit 131 so that the operating current of that value is supplied to the laser diode 60 .
- the control table contains, for example, data that indicates the oscillation threshold and the temperature dependence of the light output versus operating current characteristic of the laser diode 60 .
- the control table may further contain data that indicates the relationship between the operating current value and a temperature increase of the magnetic recording layer heated by the near-field light 48 , and data that indicates the temperature dependence of the coercivity of the magnetic recording layer.
- the control circuit 230 has the signal system for controlling the laser diode 60 , i.e., the signal system consisting of the laser ON/OFF signal and the operating current control signal, independent of the control signal system intended for read/write operations.
- This configuration makes it possible to implement various modes of energization of the laser diode 60 , not only to energize the laser diode 60 simply in association with a write operation.
- the circuit configuration of the control circuit 230 is not limited to the one shown in FIG. 10 .
- the method of manufacturing the slider 10 includes the steps of forming components of a plurality of sliders 10 other than the slider substrates 11 on a substrate that includes portions to become the slider substrates 11 of the plurality of sliders 10 , thereby fabricating a substructure that includes a plurality of rows of pre-slider portions, the pre-slider portions being intended to become the sliders 10 later; and forming the plurality of sliders 10 by cutting the substructure to separate the plurality of pre-slider portions from each other.
- the surfaces formed by the cutting are polished into the medium facing surfaces 11 a and 12 a.
- FIG. 11 to FIG. 15 each show a part of a stack of layers fabricated in the process of forming the plasmon generator 34 and the magnetic pole 35 .
- FIG. 11 to FIG. 15 each show a cross section in the position where the medium facing surface 12 a is to be formed.
- FIG. 11 shows a step of the method of forming the plasmon generator 34 and the magnetic pole 35 .
- the core 32 of the waveguide is initially formed on the clad layer 31 and then a dielectric layer 331 is formed to cover the clad layer 31 and the core 32 .
- the dielectric layer 331 is made of the same material as that of the clad layer 33 .
- FIG. 12 shows the next step.
- an etching mask is initially formed on the dielectric layer 331 .
- the etching mask has an opening that has a shape corresponding to the planar shape of the V-shaped portion 34 A of the plasmon generator 34 to be formed later.
- the dielectric layer 331 is then etched by reactive ion etching or ion milling, for example.
- a V-shaped groove 331 a is thereby formed in the dielectric layer 331 .
- the groove 331 a is formed so that its bottom end reaches the evanescent light generating surface 32 c of the core 32 .
- the etching mask is then removed.
- FIG. 13 shows the next step.
- a dielectric film 332 is formed by, for example, sputtering, so as to cover the entire top surface of the stack shown in FIG. 12 .
- the dielectric film 332 is made of the same material as that of the clad layer 33 .
- the dielectric film 332 is formed also in the groove 331 a .
- the dielectric layer 331 and the dielectric film 332 constitute the clad layer 33 .
- the groove 33 b of the clad layer 33 has a depth (dimension in the Z direction) of 200 nm, for example.
- FIG. 14 shows the next step.
- a metal film 34 P is formed by, for example, sputtering, so as to cover the entire top surface of the stack shown in FIG. 13 .
- the metal film 34 P is to become the plasmon generator 34 later.
- FIG. 15 shows the next step.
- the metal film 34 P is initially patterned by etching a part of the metal film 34 P by ion milling, for example.
- the remaining metal film 34 P becomes the plasmon generator 34 .
- the magnetic pole 35 is formed on the plasmon generator 34 by frame plating, for example.
- the thickness of the magnetic pole 35 (the distance between the bottom end of the groove 33 b and the top surface of the magnetic pole 35 ) is greater than the depth of the groove 33 b . For example, if the depth of the groove 33 b is 200 nm, the thickness of the magnetic pole 35 is 450 nm.
- the substructure is cut near the positions where the medium facing surfaces 12 a are to be formed, so that the plurality of pre-slider portions are separated from each other. Subsequently, the surfaces formed by the cutting are polished into the medium facing surfaces 12 a.
- the outer surface of the plasmon generator 34 of the present embodiment includes the plasmon exciting part 341 and the front end face 342 .
- the plasmon exciting part 341 faces the evanescent light generating surface 32 c of the core 32 with a predetermined distance therebetween.
- the front end face 342 is located in the medium facing surface 12 a .
- the front end face 342 has the near-field light generating edge 342 e lying at an end of the plasmon exciting part 341 .
- Surface plasmons are excited on the plasmon exciting part 341 through coupling with the evanescent light that occurs from the evanescent light generating surface 32 c .
- the near-field light generating edge 342 e generates near-field light based on the surface plasmons excited on the plasmon exciting part 341 .
- the present embodiment it is possible to transform the laser light that is propagated through the core 32 into near-field light with higher efficiency, as compared with the conventional technique of directly irradiating a plasmon antenna with laser light to produce near-field light from the plasmon antenna.
- the plasmon generator 34 has the V-shaped portion 34 A and the extended portions 34 B and 34 C.
- the V-shaped portion 34 A has the first and second sidewall parts 34 A 1 and 34 A 2 .
- the front end face 342 of the plasmon generator 34 includes the first and second portions 342 a and 342 b lying at the respective ends of the first and second sidewall parts 34 A 1 and 34 A 2 , the third portion 342 C lying at the end of the extended portion 34 B, and the fourth portion 342 d lying at the end of the extended portion 34 C.
- the extended portions 34 B and 34 C have a heat sink function of dissipating heat from the plasmon generator 34 to outside.
- the outer surface of the plasmon generator 34 in contact with air and other components of the thermally-assisted magnetic head can be increased in area as much as the extended portions 34 B and 34 C as compared with a case where the plasmon generator 34 does not have the extended portions 34 B and 34 C. Consequently, according to the present embodiment, the heat generated in the plasmon generator 34 can be more effectively dissipated to outside.
- the present embodiment thus makes it possible to suppress a rise in temperature of the plasmon generator 34 . This effect will be detailed below.
- the outer surface of the plasmon generator 34 includes the front end face 342 , which is exposed in the medium facing surface 12 a and is in contact with air.
- the heat of the plasmon generator 34 is dissipated at the medium facing surface 12 a by the airflow that passes between the medium facing surface 12 a and the magnetic disk 201 .
- the front end face 342 of the plasmon generator 34 in contact with air is increased in area as much as the extended portions 34 B and 34 C, i.e., as much as the third and fourth portions 342 c and 342 d , as compared with the case where the plasmon generator 34 does not have the extended portions 34 B and 34 C.
- the present embodiment thus promotes the heat dissipation from the plasmon generator 34 by means of the airflow mentioned above, and consequently makes it possible to suppress a rise in temperature of the plasmon generator 34 .
- Portions of the outer surface of the plasmon generator 34 other than the front end face 342 are in contact with other components of the thermally-assisted magnetic head. In such portions, the heat generated in the plasmon generator 34 is dissipated from the plasmon generator 34 by conduction to other components. According to the present embodiment, the portions of the outer surface of the plasmon generator 34 other than the front end face 342 are increased in area as compared with the case where the plasmon generator 34 does not have the extended portions 34 B and 34 C. The present embodiment thus promotes the heat dissipation from the plasmon generator 34 by the conduction of the heat generated in the plasmon generator 34 to other components, and consequently makes it possible to suppress a rise in temperature of the plasmon generator 34 .
- the magnetic pole 35 is in contact with the plasmon generator 34 .
- the magnetic pole 35 is also in contact with the top yoke layer 43 of high volume via the coupling layer 36 .
- the magnetic pole 35 is made of a magnetic metal material which is higher in thermal conductivity than insulating materials such as alumina. Consequently, according to the present embodiment, the heat generated in the plasmon generator 34 can be effectively dissipated through the magnetic pole 35 , the coupling layer 36 , and the top yoke layer 43 with a significant effect of suppressing a rise in temperature of the plasmon generator 34 .
- the outer edges of the extended portions 34 B and 34 C of the plasmon generator 34 lie outside the outer edges of the magnetic pole 35 . This makes it possible to make the extended portions 34 B and 34 C large without being restricted by the width of the magnetic pole 35 , so that it is possible to promote the heat dissipation from the plasmon generator 34 .
- the present embodiment it is possible to prevent the front end face 342 of the plasmon generator 34 from protruding from the medium facing surface 12 a due to an excessive rise in temperature of the plasmon generator 34 , and to prevent a reduction in use efficiency of the light in the plasmon generator 34 .
- the plasmon generator 34 of the model of the comparative example is without the extended portions 34 B and 34 C.
- the plasmon generator 34 of the model of the practical example has the extended portions 34 B and 34 C.
- W PGB and W PGC shown in FIG. 1 are 5 ⁇ m.
- T PG shown in FIG. 1 was set to 200 nm
- ⁇ shown in FIG. 2 was set to 90 degrees
- H PG shown in FIG. 3 was set to 1.2 ⁇ m
- T BF shown in FIG. 2 and FIG. 3 was set to 35 nm
- D 1 shown in FIG. 2 was set to 30 nm
- H PD shown in FIG. 3 was set to 0.5 ⁇ m.
- Energy for the plasmon generator 34 to be transformed into heat per second was set to 8.3 mW.
- Table 1 shows the results of the first simulation. From Table 1, it can be seen that both the temperature of the plasmon generator 34 and that of the core 32 are lower in the model of the practical example than in the model of the comparative example. The reason is considered to be that in the model of the practical example, the extended portions 34 B and 34 C promote the heat dissipation from the plasmon generator 34 as compared with the model of the comparative example.
- the heat dissipation from the plasmon generator 34 is promoted by the extended portions 34 B and 34 C as compared with the case where the plasmon generator 34 does not have the extended portions 34 B and 34 C.
- the present embodiment thus makes it possible to suppress a rise in temperature of the plasmon generator 34 .
- the plasmon generator 34 made of a metal is in contact with the magnetic pole 35 made of a magnetic metal material.
- the plasmon generator 34 is thus not electrically isolated. According to the present embodiment, it is therefore possible to avoid the occurrence of electrical static discharge (ESD) in the plasmon generator 34 .
- ESD electrical static discharge
- the magnetic pole 35 is disposed such that the plasmon generator 34 is interposed between the magnetic pole 35 and the core 32 .
- the end face 351 of the magnetic pole 35 for generating the write magnetic field and the near-field light generating edge 342 e of the plasmon generator 34 for generating the near-field light can be put close to each other in the medium facing surface 12 a .
- the plasmon generator 34 made of a nonmagnetic metal is interposed between the core 32 and the magnetic pole 35 , it is possible to prevent the laser light propagated through the core 32 from being absorbed by the magnetic pole 35 . This can improve the use efficiency of the laser light propagated through the core 32 .
- the first and second sidewall parts 34 A 1 and 34 A 2 are each connected to the plasmon exciting part 341 , and increase in distance from each other with increasing distance from the plasmon exciting part 341 .
- the magnetic pole 35 has the first portion 35 A interposed between the first and second sidewall parts 34 A 1 and 34 A 2 .
- the front end face 342 of the plasmon generator 34 has the first and second portions 342 a and 342 b that are connected to each other into a V-shape.
- the end face 351 of the magnetic pole 35 located in the medium facing surface 12 a has a triangular portion interposed between the first and second portions 342 a and 342 b of the front end face 342 , that is, the first portion 351 a .
- the first portion 351 a has the tip 351 c located at its bottom end. In the first portion 351 a , the tip 351 c is closest to the bottom shield layer 29 . Magnetic fluxes therefore concentrate at the vicinity of the tip 351 c of the first portion 351 a , so that a high write magnetic field occurs from the vicinity of the tip 351 c . Consequently, according to the present embodiment, the position where a high write magnetic field occurs in the first portion 351 a can be brought closer to the near-field light generating edge 342 e of the plasmon generator 34 which generates near-field light. According to the present embodiment, it is thus possible to put the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other while preventing the laser light propagated through the core 32 from being absorbed by the magnetic pole 35 .
- FIG. 16 is a front view showing a core, a plasmon generator, and a magnetic pole in the medium facing surface of the model of the first type.
- the model of the first type includes a plasmon generator 1034 and a magnetic pole 1035 , instead of the plasmon generator 34 and the magnetic pole 35 of the embodiment.
- the plasmon generator 1034 is triangular-prism-shaped.
- the outer surface of the plasmon generator 1034 includes a propagative edge and a front end face 1342 .
- the propagative edge faces the evanescent light generating surface 32 c of the core 32 with a predetermined distance therebetween.
- the front end face 1342 has a triangular shape.
- the front end face 1342 has a near-field light generating edge 1342 e lying at an end of the above-mentioned propagative edge.
- the magnetic pole 1035 does not include any portion corresponding to the first portion 35 A of the magnetic pole 35 of the embodiment.
- the magnetic pole 1035 is located on a side of the plasmon generator 1034 opposite from the core 32 , at a predetermined distance from the plasmon generator 1034 .
- the magnetic pole 1035 has an end face 1351 located in the medium facing surface 12 a .
- the end face 1351 has a rectangular shape.
- the end face 1351 has a bottom end 1351 a that is closer to the evanescent light generating surface 32 c of the core 32 .
- FIG. 17 is a front view showing a core, a plasmon generator, and a magnetic pole in the medium facing surface of the model of the second type.
- the model of the second type includes a plasmon generator 2034 and a magnetic pole 2035 , instead of the plasmon generator 34 and the magnetic pole 35 of the embodiment.
- the plasmon generator 2034 has the same configuration as that of the plasmon generator 34 of the embodiment except that there is no extended portion 34 B or 34 C.
- the magnetic pole 2035 has the same configuration as that of the magnetic pole 35 of the embodiment.
- substantially the same components as in the embodiment will be designated by like reference numerals for description.
- the outer surface of the plasmon generator 2034 includes a plasmon exciting part 341 and a front end face 342 .
- the plasmon generator 2034 has a V-shaped portion 34 A.
- the V-shaped portion 34 A has first and second sidewall parts 34 A 1 and 34 A 2 .
- the front end face 342 has first and second portions 342 a and 342 b and a near-field light generating edge 342 e . In the model of the second type, the front end face 342 does not have the third and fourth portions 342 c and 342 d of the embodiment.
- the magnetic pole 2035 has first and second portions 35 A and 35 B.
- the magnetic pole 2035 also has an end face 351 .
- the end face 351 has a first portion 351 a and a second portion 351 b .
- the first portion 351 a has a tip 351 c .
- FIG. 17 the border between the first portion 35 A (the first portion 351 a ) and the second portion 35 B (the second portion 351 b ) is shown by a chain double-dashed line.
- the model of the second type is a model for showing the relationship between the position of occurrence of the write magnetic field and the position of occurrence of the near-field light according to the embodiment.
- the plasmon generator 2034 of the second type does not include the extended portions 34 B and 34 C because the second simulation is not concerned with the extended portions 34 B and 34 C.
- FeCo was selected as the material of the magnetic poles 1035 and 2035 .
- the lengths of the plasmon generators 1034 and 2034 and those of the magnetic poles 1035 and 2035 in the X direction were each set to 3 ⁇ m.
- the length of the top yoke layer 43 in the X direction was set to 12 ⁇ m.
- the dimension of the top yoke layer 43 in the track width direction TW (Y direction) was set to 17 ⁇ m (see FIG. 9 ).
- the distance between the near-field light generating edge 1342 e of the front end face 1342 of the plasmon generator 1034 and the end face 32 b of the core 32 will be represented by the symbol T BF1 .
- the distance between the near-field light generating edge 1342 e and the bottom end 1351 a of the end face 1351 of the magnetic pole 1035 will be represented by the symbol D 21 .
- T BF1 was set to 50 nm
- D 21 was set to 120 nm.
- the distance between the near-field light generating edge 342 e of the front end face 342 of the plasmon generator 1034 and the end face 32 b of the core 32 will be represented by the symbol T BF2 .
- the distance between the near-field light generating edge 342 e and the tip 351 c will be represented by the symbol D 12 .
- the distance between the near-field light generating edge 342 e and the second portion 351 b will be represented by the symbol D 22 .
- D 22 is equal to the dimension T PG of the first and second sidewall parts 34 A 1 and 34 A 2 in the Z direction (see FIG. 1 ).
- T BF2 was set to 50 nm
- D 12 was set to 50 nm
- D 22 was set to 120 nm.
- the angle ⁇ formed between the two surfaces of the V-shaped portion 34 A on opposite sides in the track width direction (Y direction) was set to 75 degrees.
- an effective write magnetic field H eff was determined for both the model of the first type and the model of the second type.
- the effective write magnetic field refers to a write magnetic field that the magnetic pole effectively exerts on the magnetic recording layer of the magnetic disk 201 so that the magnetization of the magnetic recording layer is inverted to form a recording bit.
- the effective write magnetic field H eff is expressed by the following equation:
- H eff ⁇ ( H P 2 +H T 2 ) 1/3 +H L 2/3 / ⁇ 3/2 ,
- H P is the component of the write magnetic field in a direction perpendicular to the magnetic recording layer (X direction)
- H T is the component in the track width direction (Y direction)
- H L is the component in a track-extending direction (Z direction).
- FIG. 18 is a characteristic chart showing the effective write magnetic field H eff determined by the second simulation.
- the horizontal axis shows the position on the medium facing surface 12 a in the track-extending direction (Z direction).
- the vertical axis shows the effective write magnetic field H eff .
- the broken line shows the effective write magnetic field H eff of the model of the first type
- the solid line shows the effective write magnetic field H eff of the model of the second type.
- 0 ⁇ m indicates the position of the bottom end 1351 a of the end face 1351 of the magnetic pole 1035 of the model of the first type and the position of the border between the first portion 351 a and the second portion 351 b of the end face 351 of the magnetic pole 2035 of the model of the second type. Positions that are on the trailing end side (Z direction) relative to the 0- ⁇ m position are expressed in positive values. Positions that are on the leading end side ( ⁇ Z direction) relative to the 0- ⁇ m position are expressed in negative values.
- the near-field light generating edge 1342 e of the front end face 1342 of the plasmon generator 1034 of the model of the first type and the near-field light generating edge 342 e of the front end face 342 of the plasmon generator 2034 of the model of the second type are located at a position of ⁇ 0.12 ⁇ m.
- the effective write magnetic field H eff at the position of the near-field light generating edge 342 e was approximately twice the effective write magnetic field H eff at the position of the near-field light generating edge 1342 e in the model of the first type.
- the third simulation used the model of the second type shown in FIG. 17 .
- D 12 shown in FIG. 17 corresponds to D 1 shown in FIG. 2 .
- D 12 was varied within the range from 20 nm to 70 nm.
- the conditions of the third simulation other than D 12 will now be described.
- tantalum oxide was selected as the material of the core 32
- alumina was selected as the material of the clad layers 31 and 33
- Ag was selected as the material of the plasmon generator 34 .
- the width W WG of the core 32 in the vicinity of the plasmon generator 2034 was set to 0.5 ⁇ m.
- the thickness T WG of the core 32 was set to 0.4 ⁇ m (see FIG. 1 ).
- the width of the second portion 35 B of the magnetic pole 2035 in the medium facing surface 12 a was set to 0.24 ⁇ m.
- the length of the plasmon generator 2034 and that of the magnetic pole 2035 in the X direction were both set to 1.5 ⁇ m.
- D 22 shown in FIG. 17 (T PG shown in FIG. 1 ) was set to 175 nm.
- the radius of curvature of the near-field light generating edge 342 e was set to 15 nm.
- the laser light to be incident on and propagated through the core 32 was a Gaussian beam polarized in TM mode (where the electric field of the laser light oscillates in the direction perpendicular to the evanescent light generating surface 32 c of the core 32 ) with a wavelength of 823 nm and an incident intensity of 1.0 V 2 /m 2 .
- the peak intensity of the laser light at the end face 32 b of the core 32 (hereinafter, referred to as laser light intensity) and the peak intensity of the near-field light at the near-field light generating edge 342 e of the front end face 342 of the plasmon generator 2034 (hereinafter, referred to as near-field light intensity) were determined.
- An intensity ratio was defined and determined as the value of the near-field light intensity divided by the laser light intensity.
- the material of the core 32 being tantalum oxide, has a refractive index of 2.15 at the wavelength of 823 nm.
- the material of the clad layers 31 and 33 being alumina, has a refractive index of 1.65 at the wavelength of 823 nm.
- the rest of the conditions of the third simulation were the same as those of the model of the second type in the second simulation.
- FIG. 19 and Table 2 show the results of the third simulation.
- the horizontal axis indicates D 12
- the vertical axis indicates the near-field light intensity.
- the near-field light intensity and the intensity ratio increase with increasing D 12 .
- the intensity ratio needs to be 5 or higher in order to form only a desired recording bit on the magnetic recording layer of the magnetic disk 201 . It is therefore preferred that D 12 be 20 nm or greater. Too large D 12 , however, hinders the effect of the embodiment that the position of occurrence of the write magnetic field and the position of occurrence of the near-field light can be located close to each other. It has been experimentally known that D 12 of 70 nm or less makes it possible to apply a write magnetic field having a desired gradient to the portion of the magnetic recording layer of the magnetic disk 201 that is sufficiently heated by the near-field light.
- D 12 or D 1 shown in FIG. 2 , fall within the range of 20 to 70 nm.
- D 1 is preferably 30 nm or greater, and yet preferably 40 nm or greater, in order to ensure an intensity ratio of 5 or higher.
- T PG shown in FIG. 1 was varied to be 170 nm, 200 nm, and 230 nm.
- the light density distribution of the near-field light at the surface of a magnetic recording medium located 8 nm away from the medium facing surface 12 a was determined by using a three-dimensional finite-difference time-domain method similar to that used in the third simulation. From the light density distribution, the spot diameter of the near-field light (hereinafter, referred to as light spot diameter) and the maximum light density were determined. The light spot diameter was defined as the full width at half maximum in the light density distribution. The rest of the conditions of the fourth simulation were the same as those of the model of the practical example in the first simulation.
- Table 3 shows the results of the fourth simulation. It can be seen from Table 3 that T PG of 200 nm or greater can make the maximum light density higher than when T PG is 170 nm, and make both the maximum light density and the light spot diameter constant. It is therefore preferred that T PG be 200 nm or greater. Too large T PG , on the other hand, makes the V-shaped groove 331 a shown in FIG. 12 too deep, thereby making it difficult to form the groove 331 a . In such a point of view, it is preferred that T PG be 400 nm or less. Consequently, it is preferred that T PG fall within the range of 200 to 400 nm.
- FIG. 20 is a perspective view showing the core of the waveguide, the plasmon generator, and the magnetic pole of the thermally-assisted magnetic recording head according to the present embodiment.
- FIG. 21 is a plan view showing the plasmon exciting part of the plasmon generator shown in FIG. 20 as viewed from above.
- the plasmon generator 34 of the present embodiment has a first portion 34 D and a second portion 34 E, instead of the V-shaped portion 34 A of the first embodiment.
- the first portion 34 D has an end face located in the medium facing surface 12 a .
- the second portion 34 E is located farther from the medium facing surface 12 a than is the first portion 34 D, such that the second portion 34 E is continuous with the first portion 34 D.
- the border between the first portion 34 D and the second portion 34 E is shown by a chain double-dashed line.
- the first portion 34 D has a bottom part 34 D 1 that is shaped like a plate and faces the evanescent light generating surface 32 c , and first and second sidewall parts 34 D 2 and 34 D 3 that are each shaped like a plate.
- the sidewall parts 34 D 2 and 34 D 3 are located farther from the evanescent light generating surface 32 c than is the bottom part 34 D 1 .
- the bottom part 34 D 1 connects the first and second sidewall parts 34 D 2 and 34 D 3 to each other at their respective edges closer to the evanescent light generating surface 32 c.
- the bottom part 34 D 1 has a width that decreases with decreasing distance to the medium facing surface 12 a , the width being in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction).
- the bottom part 34 D 1 has an end located in the medium facing surface 12 a . At this end of the bottom part 34 D 1 , the bottom part 34 D 1 has a zero width and the respective bottom ends of the first and second sidewall parts 34 D 2 and 34 D 3 are in contact with each other.
- the distance between the first and second sidewall parts 34 D 2 and 34 D 3 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c increases with increasing distance from the evanescent light generating surface 32 c , and decreases with decreasing distance to the medium facing surface 12 a.
- the second portion 34 E has a bottom part 34 E 1 that is continuous with the bottom part 34 D 1 of the first portion 34 D, a first sidewall part 34 E 2 that is continuous with the first sidewall part 34 D 2 of the first portion 34 D, and a second sidewall part 34 E 3 that is continuous with the second sidewall part 34 D 3 of the first portion 34 D.
- the bottom part 34 E 1 has a constant width in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) regardless of the distance from the medium facing surface 12 a.
- the distance between the first and second sidewall parts 34 E 2 and 34 E 3 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c increases with increasing distance from the evanescent light generating surface 32 c , but does not change according to the distance from the medium facing surface 12 a.
- the first portion 34 D and the second portion 34 E of the plasmon generator 34 form inside a space for accommodating a part of the magnetic pole 35 .
- the extended portions 34 B and 34 C spread out from the top ends of the first portion 34 D and the second portion 34 E in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction).
- the outer edges of the extended portions 34 B and 34 C lie outside the outer edges of the magnetic pole 35 .
- the second portion 35 B of the magnetic pole 35 is in contact with the extended portions 34 B and 34 C.
- the plasmon exciting part 341 of the present embodiment includes a flat surface part 341 b instead of the propagative edge 341 a of the first embodiment.
- the flat surface part 341 b includes a width changing portion 341 b 1 and a constant width portion 341 b 2 .
- the width changing portion 341 b 1 is formed by a surface of the bottom part 34 D 1 of the first portion 34 D that is closer to the evanescent light generating surface 32 c .
- the constant width portion 341 b 2 is formed by a surface of the bottom part 34 E 1 of the second portion 34 E that is closer to the evanescent light generating surface 32 c .
- the border between the width changing portion 341 b 1 and the constant width portion 341 b 2 is shown by a chain double-dashed line.
- the width changing portion 341 b 1 has a width that decreases with decreasing distance to the medium facing surface 12 a , the width being in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction).
- the width changing portion 341 b 1 has a front end part that is located in the medium facing surface 12 a , and two sides that are opposite in the direction of the width (Y direction).
- the two sides of the width changing portion 341 b 1 form the same angle with respect to the direction perpendicular to the medium facing surface 12 a (X direction). The angle falls within the range of 3 to 50 degrees, and preferably within the range of 10 to 25 degrees.
- the constant width portion 341 b 2 is located farther from the medium facing surface 12 a than is the width changing portion 341 b 1 , such that the constant width portion 341 b 2 is continuous with the width changing portion 341 b 1 .
- the constant width portion 341 b 2 has a constant width in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) regardless of the distance from the medium facing surface 12 a.
- first portion 342 a and the second portion 342 b of the front end face 342 lie at respective ends of the first and second sidewall parts 34 D 1 and 34 D 2 of the first portion 34 D, and are connected to each other into a V-shape.
- the first portion 35 A of the magnetic pole 35 is accommodated in the space formed by the first portion 34 D and the second portion 34 E of the plasmon generator 34 .
- the first portion 35 A includes a front part 35 A 1 and a rear part 35 A 2 .
- the front part 35 A 1 is accommodated in the space formed by the first portion 34 D (the bottom part 34 D 1 , the first sidewall part 34 D 2 , and the second sidewall part 34 D 3 ) of the plasmon generator 34 .
- the rear part 35 A 2 is accommodated in the space formed by the second portion 34 E (the bottom part 34 E 1 , the first sidewall part 34 E 2 , and the second sidewall part 34 E 3 ) of the plasmon generator 34 .
- the front part 35 A 1 is interposed between the first and second sidewall parts 34 D 2 and 34 D 3 of the first portion 34 D of the plasmon generator 34 , and is contact with the bottom part 34 D 1 , the first sidewall part 34 D 2 , and the second sidewall part 34 D 3 .
- the width of the front part 35 A 1 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) increases with increasing distance from the evanescent light generating surface 32 c , and decreases with decreasing distance to the medium facing surface 12 a.
- the front part 35 A 1 has an end face located in the medium facing surface 12 a .
- the first portion 351 a of the end face 351 of the magnetic pole 35 located in the medium facing surface 12 a is formed by the end face of the front part 35 A 1 .
- the rear part 35 A 2 is interposed between the first and second sidewall parts 34 E 2 and 34 E 3 of the second portion 34 E of the plasmon generator 34 , and is contact with the bottom part 34 E 1 , the first sidewall part 34 E 2 , and the second sidewall part 34 E 3 .
- the width of the rear part 35 A 2 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) increases with increasing distance from the evanescent light generating surface 32 c , but does not change according to the distance from the medium facing surface 12 a.
- the plasmon generator 34 need not necessarily have the second portion 34 E. If the plasmon generator 34 does not have the second portion 34 E, the first portion 35 A of the magnetic pole 35 does not have the rear part 35 A 2 .
- the plasmon generator 34 has the extended portions 34 B and 34 C. This promotes the heat dissipation from the plasmon generator 34 , and thereby makes it possible to suppress a rise in temperature of the plasmon generator 34 .
- the second portion 35 B of the magnetic pole 35 is in contact with the extended portions 34 B and 34 C of the plasmon generator 34 .
- the heat generated in the plasmon generator 34 can thus be effectively dissipated through the magnetic pole 35 , the coupling layer 36 , and the top yoke layer 43 .
- the outer edges of the extended portions 34 B and 34 C lie outside the outer edges of the magnetic pole 35 . This makes it possible, as in the first embodiment, to make the extended portions 34 B and 34 C large without being restricted by the width of the magnetic pole 35 , so that it is possible to promote the heat dissipation from the plasmon generator 34 .
- the plasmon exciting part 341 of the plasmon generator 34 includes the flat surface part 341 b .
- the flat surface part 341 b includes the width changing portion 341 b 1 .
- the width of the width changing portion 341 b 1 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) decreases with decreasing distance to the medium facing surface 12 a .
- the surface plasmons excited on the flat surface part 341 b are gradually transformed into edge plasmons, which are surface plasmons to propagate along the two sides of the width changing portion 341 b 1 that are opposite in the direction of the width (Y direction), while propagating over the width changing portion 341 b 1 .
- the surface plasmons (including edge plasmons) propagating over the width changing portion 341 b 1 reach the near-field light generating edge 342 e.
- the propagating plasmons increase in electric field intensity. This is presumably based on the following first and second principles. Initially, a description will be given of the first principle.
- the wave number of the surface plasmons propagating over the width changing portion 341 b 1 increases as the width of the width changing portion 341 b 1 decreases. As the wave number of the surface plasmons increases, the speed of travel of the surface plasmons decreases. This consequently increases the energy density of the surface plasmons and enhances the electric field-intensity of the surface plasmons.
- the surface plasmons propagate over the width changing portion 341 b 1 , some of the surface plasmons impinge on the two sides of the width changing portion 341 b 1 that are opposite in the direction of the width (Y direction) to scatter, thereby generating a plurality of plasmons with different wave numbers. Some of the plurality of plasmons thus generated are transformed into edge plasmons having a wave number higher than that of the surface plasmons propagating over a flat surface. In this way, the surface plasmons are gradually transformed into the edge plasmons to propagate along the two sides, whereby the edge plasmons gradually increase in electric field intensity.
- the edge plasmons are higher in wave number and lower in speed of travel. Consequently, the transformation of the surface plasmons into the edge plasmons increases the energy density of the plasmons.
- the foregoing transformation of the surface plasmons into the edge plasmons is accompanied by the generation of new surface plasmons based on the evanescent light occurring from the evanescent light generating surface 32 c .
- the new surface plasmons are also transformed into edge plasmons.
- the edge plasmons increase in electric field intensity. In this way, it is possible to obtain edge plasmons that are higher in electric field intensity than the surface plasmons originally generated.
- the surface plasmons propagating over the flat surface and the edge plasmons having a wave number higher than that of the surface plasmons coexist. It can be considered that both the surface plasmons and the edge plasmons increase in electric field intensity in the width changing portion 341 b 1 based on the first and second principles described above. In the width changing portion 341 b 1 , the electric field intensity of the plasmons can thus be enhanced as compared with a case where either one of the first principle and the second principle is in operation.
- the flat surface part 341 b of the plasmon exciting part 341 of the plasmon generator 34 further includes the constant width portion 341 b 2 .
- the flat surface part 341 b does not include the constant width portion 341 b 2
- the width changing portion 341 b 1 extends up to the end of the flat surface part 341 b opposite from the medium facing surface 12 a .
- the maximum width of the flat surface part 341 b is greater as compared with the case where the flat surface part 341 b includes the constant width portion 341 b 2 .
- the width W WG of the core 32 in the vicinity of the plasmon generator 34 needs to be increased to the maximum width of the flat surface part 341 b .
- the flat surface part 341 b includes the constant width portion 341 b 2 , and it is therefore possible to make the width W WG of the core 32 in the vicinity of the plasmon generator 34 smaller than that in the case where the flat surface part 341 b does not include the constant width portion 341 b 2 .
- the present embodiment it is therefore possible to bring at least a part of the core 32 in the vicinity of the plasmon generator 34 into a single mode that is capable of propagating only a single mode of light. Consequently, it is possible to improve the use efficiency of the laser light that is propagated through the core 32 .
- the first portion 34 D of the plasmon generator 34 has the bottom part 34 D 1 and the first and second sidewall parts 34 D 2 and 34 D 3 .
- the width of the bottom part 34 D 1 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) decreases with decreasing distance to the medium facing surface 12 a .
- the distance between the first and second sidewall parts 34 D 2 and 34 D 3 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) increases with increasing distance from the evanescent light generating surface 32 c , and decreases with decreasing distance to the medium facing surface 12 a .
- the magnetic pole 35 includes the front part 35 A 1 that is interposed between the first and second sidewall parts 34 D 2 and 34 D 3 and in contact with the bottom part 34 D 1 , the first sidewall part 34 D 2 and the second sidewall part 34 D 3 .
- the width of the front part 35 A 1 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) decreases with decreasing distance to the medium facing surface 12 a . Consequently, according to the present embodiment, magnetic fluxes passing through the magnetic pole 35 can be concentrated as they approach the medium facing surface 12 a . This makes it possible to produce a high write magnetic field from the first portion 351 a of the end face 351 .
- the present embodiment may be modified so that the plasmon generator of the invention is configured as in the following modification example.
- the V-shaped portion 34 A of the first embodiment is provided between the medium facing surface 12 a and the first portion 34 D.
- the plasmon exciting part 341 includes the propagative edge 341 a and the flat surface part 3431 b .
- the medium facing surface 12 a is formed by polishing a surface that is formed by cutting the substructure. In such a case, the position of the medium facing surface 12 a may slightly vary.
- the plasmon generator 34 is designed not to have the V-shaped portion 34 A or the propagative edge 341 a so that the ends of the first portion 34 D and the width changing portion 341 b 1 are located in the medium facing surface 12 a . If so, variations in the position of the medium facing surface 12 a change the shape of the front end face 342 of the plasmon generator 34 , or the shape of the near-field light generating edge 342 e in particular. As a result, the near-field light occurring from the plasmon generator 34 can vary in characteristic. In contrast, according to the modification example described above, the plasmon generator 34 has the V-shaped portion 34 A and the propagative edge 341 a .
- the first portion 35 A of the magnetic pole 35 has a triangular-prism-shaped portion that is accommodated in the V-shaped portion 34 A.
- the width of the triangular-prism-shaped portion in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) does not change according to the distance from the medium facing surface 12 a .
- FIG. 22 is a front view showing a part of the medium facing surface of the head unit of the thermally-assisted magnetic recording head according to the present embodiment.
- FIG. 23 is a cross-sectional view showing the core of the waveguide, the plasmon generator, and the magnetic pole of the thermally-assisted magnetic recording head according to the present embodiment.
- the thermally-assisted magnetic recording head according to the present embodiment has a plasmon generator 84 and a magnetic pole 85 , instead of the plasmon generator 34 and the magnetic pole 35 of the first embodiment.
- the plasmon generator 84 is made of the same material as that of the plasmon generator 34 of the first embodiment.
- the magnetic pole 85 is made of the same material as that of the magnetic pole 35 of the first embodiment.
- the plasmon generator 84 has an outer surface that includes a plasmon exciting part 841 and a front end face 842 .
- the plasmon exciting part 841 faces the evanescent light generating surface 32 c of the core 32 with a predetermined distance therebetween.
- the front end face 842 is located in the medium facing surface 12 a .
- the plasmon generator 84 further has a V-shaped portion 84 A that has an end face located in the medium facing surface 12 a .
- the V-shaped portion 84 A has a first sidewall part 84 A 1 and a second sidewall part 84 A 2 that are each connected to the plasmon exciting part 841 , and that increase in distance from each other with increasing distance from the plasmon exciting part 841 .
- the shapes and locations of the first and second sidewall parts 84 A 1 and 84 A 2 are the same as those of the first and second sidewall parts 34 A 1 and 34 A 2 of the first embodiment.
- the plasmon generator 84 further has an extended portion 84 B and an extended portion 84 C.
- the extended portion 84 B is connected to an edge of the first sidewall part 84 A 1 opposite from the plasmon exciting part 841 .
- the extended portion 84 C is connected to an edge of the second sidewall part 84 A 2 opposite from the plasmon exciting part 841 . From the edge of the first sidewall part 84 A 1 opposite from the plasmon exciting part 841 , the extended portion 84 B extends parallel to the evanescent light generating surface 32 c and away from both the first and second sidewall parts 84 A 1 and 84 A 2 .
- the extended portion 84 C extends parallel to the evanescent light generating surface 32 c and away from both the first and second sidewall parts 84 A 1 and 84 A 2 .
- Each of the extended portions 84 B and 84 C has a constant width in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) regardless of the distance from the medium facing surface 12 a .
- the width of the extended portion 84 B is greater than that of the extended portion 84 C. Note that the plasmon generator 84 need not necessarily have the extended portion 84 C.
- the plasmon exciting part 841 includes a propagative edge 841 a that lies at an end of the connected first and second sidewall parts 84 A 1 and 84 A 2 closer to the evanescent light generating surface 32 c .
- the shape and location of the propagative edge 841 a are the same as those of the propagative edge 341 a of the first embodiment.
- the front end face 842 has a first portion 842 a and a second portion 842 b that lie at respective ends of the first and second sidewall parts 84 A 1 and 84 A 2 and are connected to each other into a V-shape, a third portion 842 c that lies at an end of the extended portion 84 B, a fourth portion 842 d that lies at an end of the extended portion 84 C, and a near-field light generating edge 842 e that lies at an end of the plasmon exciting part 841 (propagative edge 841 a ).
- the shape and location of the near-field light generating edge 842 e are the same as those of the near-field light generating edge 342 e of the first embodiment.
- the thermally-assisted magnetic recording head further includes a conductor 86 made of a conductive material.
- the conductor 86 has a Seebeck coefficient different from that of the plasmon generator 84 , and is in contact with the plasmon generator 84 .
- the conductor 86 makes contact with the plasmon generator 84 at least on a virtual straight line L, the virtual straight line L passing through the near-field light generating edge 842 e and extending in the direction perpendicular to the evanescent light generating surface 32 c .
- the conductor 86 is disposed on the V-shaped portion 84 A and the extended portions 84 B and 84 C of the plasmon generator 84 and makes contact with such portions.
- heat absorption by the Peltier effect occurs in a contact area between the plasmon generator 84 and the conductor 86 when a current is made to flow from one of the plasmon generator 84 and the conductor 86 , the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area.
- the difference between the Seebeck coefficient of the plasmon generator 84 and that of the conductor 86 be as great as possible.
- the Seebeck coefficient of the plasmon generator 84 and that of the conductor 86 may have opposite signs.
- the plasmon generator 84 may be made of Au, and the conductive material used to form the conductor 86 may contain at least one of Co, Ni, and a CuNi alloy.
- Au has a Seebeck coefficient of 1.9 ⁇ V/K at 300 K
- Co has a Seebeck coefficient of ⁇ 30.8 ⁇ V/K at 300 K.
- the plasmon generator 84 made of Au thus has a Seebeck coefficient of 1.9 ⁇ V/K at 300 K. If the conductor 86 is made of Co, the conductor 86 has a Seebeck coefficient of ⁇ 30.8 ⁇ V/K at 300K.
- the plasmon generator 84 is made of Au, Co is an appropriate conductive material for forming the conductor 86 . Like Co, each of Ni and a CuNi alloy has a negative Seebeck coefficient of a high absolute value. If the plasmon generator 84 is made of Au, then Ni and a CuNi alloy are also appropriate as the conductive material for forming the conductor 86 , aside from Co. When the plasmon generator 84 is made of Au, the conductive material used to form the conductor 86 may be an alloy that contains at least one of Co, Ni, and a CuNi alloy, and that is lower in Seebeck coefficient than Au.
- the dimension of the conductor 86 on the virtual straight line L shown in FIG. 22 will be represented by the symbol D 2 .
- Too small D 2 makes the resistance of the conductor 86 too high.
- Too large D 2 hinders the effect of the embodiment that the position of occurrence of the write magnetic field and the position of occurrence of the near-field light can be located close to each other. In such a point of view, it is preferred that D 2 fall within the range of 20 to 50 nm.
- the conductor 86 is greater than the V-shaped portion 84 A of the plasmon generator 84 in dimension in the track width direction TW (Y direction) at the medium facing surface 12 a .
- the dimension of the conductor 86 in the track width direction TW is 0.6 ⁇ m, for example.
- the conductor 86 is greater than the plasmon generator 84 in length in the X direction.
- the length of the conductor 86 in the X direction is 1.2 ⁇ m, for example.
- the conductor 86 includes a V-shaped portion 86 A that has an end face located in the medium facing surface 12 a .
- the V-shaped portion 86 A is arranged along the inner surfaces of the V-shaped portion 84 A of the plasmon generator 84 and extends in the direction perpendicular to the medium facing surface 12 a (X direction).
- the V-shaped portion 86 A is V-shaped in cross section parallel to the medium facing surface 12 a.
- the conductor 86 further includes extended portions 86 B and 86 C that spread out from the top ends of the V-shaped portion 86 A of the conductor 86 in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction).
- the extended portion 86 B is arranged along the top surface of the extended portion 84 B of the plasmon generator 84 .
- the extended portion 86 C is arranged along the top surface of the extended portion 84 C of the plasmon generator 84 and the top surface 33 a of the clad layer 33 .
- Each of the extended portions 86 B and 86 C has a constant width in the direction parallel to the medium facing surface 12 a and the evanescent light generating surface 32 c (Y direction) regardless of the distance from the medium facing surface 12 a .
- the width of the extended portion 86 B is smaller than that of the extended portion 84 B of the plasmon generator 84 .
- the width of the extended portion 86 C is greater than that of the extended portion 86 B and greater than that of the extended portion 84 C of the plasmon generator 84 . Note that the conductor 86 need not necessarily have the extended portion 86 B.
- the magnetic pole 85 is disposed on the conductor 86 so that at least a part of the conductor 86 , that is, the V-shaped portion 86 A, is interposed between the plasmon generator 84 and the magnetic pole 85 .
- the magnetic pole 85 has a first portion 85 A and a second portion 85 B.
- the second portion 85 B is located farther from the evanescent light generating surface 32 c of the core 32 than is the first portion 85 A.
- the border between the first portion 85 A and the second portion 85 B is shown by a chain double-dashed line.
- the first portion 85 A has a triangular-prism-shaped part in the vicinity of the medium facing surface 12 a .
- the triangular-prism-shaped part of the first portion 85 A is interposed between the first and second sidewall parts 84 A 1 and 84 A 2 of the plasmon generator 84 .
- the V-shaped portion 86 A of the conductor 86 is interposed between the triangular-prism-shaped part of the first portion 85 A and the first and second sidewall parts 84 A 1 and 84 A 2 .
- the magnetic pole 85 has an end face 851 located in the medium facing surface 12 a .
- the end face 851 includes a first portion 851 a and a second portion 851 b .
- the first portion 851 a is the end face of the first portion 85 A.
- the second portion 851 b is the end face of the second portion 85 B.
- the first portion 851 a has a triangular shape and is interposed between the first and second portions 842 a and 842 b of the front end face 842 of the plasmon generator 84 .
- the end face of the V-shaped portion 86 A of the conductor 86 is interposed between the first portion 851 a and the first and second portions 842 a and 842 b of the front end face 842 .
- the end face 851 a has a tip 851 c located at its bottom end.
- the thermally-assisted magnetic recording head further includes a first electrode 87 that is electrically connected to the extended portion 84 B of the plasmon generator 84 , and a second electrode 88 that is electrically connected to the extended portion 86 C of the conductor 86 .
- the first and second electrodes 87 and 88 are located on opposite sides of the magnetic pole 85 in the track width direction TW, each at a distance from the magnetic pole 85 . Not-shown leads are connected to the first and second electrodes 87 and 88 , respectively.
- the first and second electrodes 87 and 88 are made of a conductive material.
- the first and second electrodes 87 and 88 may be made of the same material (magnetic metal material) as that of the magnetic pole 85 .
- the thermally-assisted magnetic recording head further includes insulating films 81 and 82 .
- the insulating films 81 and 82 cover the respective portions of the plasmon generator 84 and the conductor 86 that are interposed between the magnetic pole 85 and the first and second electrodes 87 and 88 .
- the insulating films 81 and 82 extend in the direction perpendicular to the medium facing surface 12 a (X direction).
- the insulating films 81 and 82 each have a thickness (dimension in the Z direction) of 50 nm, for example.
- the insulating films 81 and 82 are each made of an insulating material such as alumina.
- FIG. 24A to FIG. 26A , FIG. 24B to FIG. 26B , and FIG. 27 to FIG. 29 describe an example of the method of forming the plasmon generator 84 , the magnetic pole 85 and the conductor 86 .
- FIG. 24A to FIG. 26A are plan views each showing a part of a stack of layers fabricated in the process of forming the plasmon generator 84 , the magnetic pole 85 and the conductor 86 .
- FIG. 24B to FIG. 26B , and FIG. 27 to FIG. 29 are cross-sectional views each showing a part of the stack of layers fabricated in the process of forming the plasmon generator 84 , the magnetic pole 85 and the conductor 86 .
- the symbol ABS indicates the position where the medium facing surface 12 a is to be formed.
- FIG. 24B to FIG. 26B , and FIG. 27 to FIG. 29 each show a cross section in the position ABS.
- the method of forming the plasmon generator 84 , the magnetic pole 85 and the conductor 86 is the same as in the first embodiment up to the step of forming the clad layer 33 as shown in FIG. 13 .
- FIG. 24A and FIG. 24B show the next step.
- a metal film that is to become the plasmon generator 84 later is initially formed by, for example, sputtering, so as to cover the entire top surface of the stack shown in FIG. 13 .
- the metal film is patterned by etching a part of the metal film by ion milling, for example. As a result, the remaining metal film becomes the plasmon generator 84 .
- FIG. 25A and FIG. 25B show the next step.
- the conductor 86 is formed by lift-off, for example.
- a mask having an opening that has a shape corresponding to the planar shape of the conductor 86 to be formed later is initially formed.
- the mask can be formed by patterning a photoresist layer by photolithography, for example.
- a metal film to become the conductor 86 later is then formed by, for example, sputtering, so as to cover the entire top surface of the stack shown in FIG. 24A and FIG. 24B .
- the mask is lifted off. The remaining metal film thereby becomes the conductor 86 .
- FIG. 26A and FIG. 26B show the next step.
- the insulating layers 81 and 82 are selectively formed on the plasmon generator 84 and the conductor 86 .
- FIG. 27 shows the next step.
- an electrode film 89 is formed by, for example, sputtering, so as to cover the entire top surface of the stack shown in FIG. 26A and FIG. 26B .
- the material of the electrode film 89 is FeCo, for example.
- FIG. 28 shows the next step.
- plating films 85 C, 87 C, and 88 C are formed by, for example, frame plating, using the electrode film 89 as the electrode.
- the plating film 85 C has a shape corresponding to the planar shape of the second portion 85 B of the magnetic pole 85 .
- the plating film 87 C has a shape corresponding to the planar shape of the first electrode 87 .
- the plating film 88 C has a shape corresponding to the planar shape of the second electrode 88 .
- the plating film 85 C is formed also on a part of the electrode film 89 located on the insulating film 81 and on a part of the electrode film 89 located on the insulating film 82 .
- the plating film 87 C is formed also on a part of the electrode film 89 located on the insulating film 81 .
- the plating film 88 C is formed also on a part of the electrode film 89 located on the insulating film 82 .
- FIG. 29 shows the next step.
- the electrode film 89 is etched by, for example, ion milling, using the plating films 85 C, 87 C and 88 C as the etching mask, until the top surface 33 a of the clad layer 33 and the top surfaces of the insulating films 81 and 82 are exposed.
- the plating film 85 C and a first portion 89 A of the electrode film 89 that remains below the plating film 85 C form the magnetic pole 85 .
- the plating film 87 C and a second portion 89 B of the electrode film 89 that remains below the plating film 87 C form the first electrode 87 .
- the plating film 88 C and a third portion 89 C of the electrode film 89 that remains below the plating film 88 C form the second electrode 88 .
- the insulating films 81 and 82 prevent the portions of the plasmon generator 84 and the conductor 86 interposed between the magnetic pole 85 and the first and second electrodes 87 and 88 from being etched during the etching of the electrode film 89 .
- the magnetic pole 85 , the first electrode 87 and the second electrode 88 are formed simultaneously in the steps shown in FIG. 27 to FIG. 29 .
- the formation of the magnetic pole 85 and the formation of the first and second electrodes 87 and 88 need not necessarily be simultaneous.
- the thermally-assisted magnetic recording head according to the present embodiment includes the conductor 86 made of a conductive material, the conductor 86 having a Seebeck coefficient different from that of the plasmon generator 84 and being in contact with the plasmon generator 84 .
- heat absorption by the Peltier effect occurs in the contact area between the plasmon generator 84 and the conductor 86 when a current is made to flow from one of the plasmon generator 84 and the conductor 86 , the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area.
- a voltage for generating the current that causes the heat absorption by the Peltier effect in the contact area is applied to the first and second electrodes 87 and 88 .
- the plasmon generator 84 is made of Au and the conductor 86 is made of Co, the current is passed through the second electrode 88 , the conductor 86 , the plasmon generator 84 , and the first electrode 87 in this order. According to the present embodiment, it is thereby possible to cool the plasmon generator 84 .
- ⁇ AB is the Peltier coefficient
- I is the current that passes through the contact area.
- the Peltier coefficient ⁇ AB is given by the following equation (2):
- ⁇ AB ( ⁇ A ⁇ B ) ⁇ T (2)
- ⁇ A is the Seebeck coefficient of the plasmon generator 84 (Au)
- ⁇ B is the Seebeck coefficient of the conductor 86 (Co).
- T is the absolute temperature.
- Au has a Seebeck coefficient of 1.9 ⁇ V/K at 300 K
- Co has a Seebeck coefficient of ⁇ 30.8 ⁇ V/K at 300 K.
- the cooling operation by the Peltier effect is added to the heat dissipating operation by the extended portions 84 B and 84 C of the plasmon generator 84 . This allows a further suppression of a rise in temperature of the plasmon generator 84 .
- the first electrode 87 is in contact with the extended portion 84 B of the plasmon generator 84
- the second electrode 88 is in contact with the extended portion 84 C of the conductor 86 . Consequently, according to the present embodiment, the heat generated in the plasmon generator 84 can be dissipated through the first electrode 87 , and through the conductor 86 and the second electrode 88 .
- FIG. 30 is a front view showing a part of the medium facing surface of the head unit of the thermally-assisted magnetic recording head according to the present embodiment.
- the thermally-assisted magnetic recording head according to the present embodiment does not have the first and second electrodes 87 and 88 of the third embodiment.
- the thermally-assisted magnetic recording head according to the present embodiment has a plasmon generator 94 , a magnetic pole 95 , a conductor 96 , and insulating films 91 and 92 , instead of the plasmon generator 84 , the magnetic pole 85 , the conductor 86 , and the insulating films 81 and 82 of the third embodiment.
- the plasmon generator 94 is made of the same material as that of the plasmon generator 84 of the third embodiment.
- the magnetic pole 95 is made of the same material as that of the magnetic pole 85 of the third embodiment.
- the conductor 96 is made of the same material as that of the conductor 86 of the third embodiment.
- the insulating films 91 and 92 are made of the same material as that of the insulating films 81 and 82 of the third embodiment.
- the plasmon generator 94 has an outer surface that includes a plasmon exciting part 941 and a front end face 942 .
- the plasmon exciting part 941 faces the evanescent light generating surface 32 c of the core 32 with a predetermined distance therebetween.
- the front end face 942 is located in the medium facing surface 12 a .
- the plasmon generator 94 further has a V-shaped portion 94 A that has an end face located in the medium facing surface 12 a .
- the V-shaped portion 94 A has a first sidewall part 94 A 1 and a second sidewall part 94 A 2 that are each connected to the plasmon exciting part 941 , and that increase in distance from each other with increasing distance from the plasmon exciting part 941 .
- the shapes and locations of the first and second sidewall parts 94 A 1 and 94 A 2 are the same as those of the first and second sidewall parts 84 A 1 and 84 A 2 of the third embodiment.
- the plasmon generator 94 further has an extended portion 94 B and an extended portion 94 C.
- the extended portion 94 B is connected to an edge of the first sidewall part 94 A 1 opposite from the plasmon exciting part 941 .
- the extended portion 94 C is connected to an edge of the second sidewall part 94 A 2 opposite from the plasmon exciting part 941 .
- a not-shown lead is connected to the extended portion 94 B.
- the shapes and locations of the extended portions 94 B and 94 C are the same as those of the extended portions 84 B and 84 C of the third embodiment. Note that the plasmon generator 94 need not necessarily have the extended portion 94 C.
- the front end face 942 has a first portion 942 a and a second portion 942 b that lie at respective ends of the first and second sidewall parts 94 A 1 and 94 A 2 and are connected to each other into a V-shape, a third portion 942 c that lies at an end of the extended portion 94 B, a fourth portion 942 d that lies at an end of the extended portion 94 C, and a near-field light generating edge 942 e that lies at an end of the plasmon exciting part 941 .
- the shape and location of the near-field light generating edge 942 e are the same as those of the near-field light generating edge 842 e of the third embodiment.
- the insulating film 91 is arranged along the inner surface of the first sidewall part 94 A 1 and the top surface of the extended portion 94 B of the plasmon generator 94 , and covers the joint between the first sidewall part 94 A 1 and the extended portion 94 B and its vicinity.
- the insulating film 92 is arranged along the inner surface of the second sidewall part 94 A 2 and the top surface of the extended portion 94 C of the plasmon generator 94 , and covers the joint between the second sidewall part 94 A 2 and the extended portion 94 C and its vicinity.
- the conductor 96 is arranged along the inner surfaces of the V-shaped portion 94 A and the top surfaces of the insulating films 91 and 92 .
- the conductor 96 makes contact with the plasmon generator 94 at least on a virtual straight line L, the virtual straight line L passing through the near-field light generating edge 942 e and extending in the direction perpendicular to the evanescent light generating surface 32 c .
- the conductor 96 makes contact with the plasmon generator 94 on the virtual straight line L passing through the near-field light generating edge 942 e and extending in the direction perpendicular to the evanescent light generating surface 32 c , and in the vicinity of the virtual straight line L.
- the magnetic pole 95 is disposed on the conductor 96 so that the conductor 96 is interposed between the plasmon generator 94 and the magnetic pole 95 .
- the magnetic pole 95 has a portion interposed between the first and second sidewall parts 94 A 1 and 94 A 2 of the plasmon generator 94 . Between this portion of the magnetic pole 95 and the first and second sidewall parts 94 A 1 and 94 A 2 , there are interposed respective portions of the conductor 96 and the insulating films 91 and 92 .
- the magnetic pole 95 has an end face 951 located in the medium facing surface 12 a .
- the end face 951 has a portion interposed between the first and second portions 942 a and 942 b of the front end face 942 of the plasmon generator 94 .
- the end face 951 has a tip 951 c located at its bottom end.
- a not-shown lead is connected to the magnetic pole 95 .
- the conductor 96 is electrically connected to the magnetic pole 95 .
- the magnetic pole 95 is formed by frame plating, for example.
- the conductor 96 may be used as an electrode film when forming the magnetic pole 95 by frame plating.
- the conductor 96 makes contact with the plasmon generator 94 at least on the virtual straight line L that passes through the near-field light generating edge 942 e and extends in the direction perpendicular to the evanescent light generating surface 32 c .
- heat absorption by the Peltier effect occurs in the contact area between the plasmon generator 94 and the conductor 96 when a current is made to flow from one of the plasmon generator 94 and the conductor 96 , the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area.
- the conductor 96 is electrically connected to the magnetic pole 95 .
- a voltage for generating the current that causes the heat absorption by the Peltier effect in the contact area is applied to the plasmon generator 94 and the magnetic pole 95 . According to the present embodiment, it is thereby possible to cool the plasmon generator 94 .
- the insulating films 91 and 92 insulate part of the plasmon generator 94 from part of the conductor 96 so that the contact area between the plasmon generator 94 and the conductor 96 is formed in a limited area close to the near-field light generating edge 942 e . According to the present embodiment, it is therefore possible to cause the heat absorption by the Peltier effect in proximity to the near-field light generating edge 942 e where the plasmon generator 94 becomes highest in temperature.
- the near-field light generating edge 942 e of the plasmon generator 94 can be cooled more efficiently as compared with the case where the contact area between the plasmon generator 94 and the conductor 96 has a greater area than in the embodiment, provided that the amount of heat absorption by the Peltier effect is the same. As a result, it is possible to suppress a rise in temperature of the near-field light generating edge 942 e where the plasmon generator 94 becomes highest in temperature.
- the present invention is not limited to the foregoing embodiments, and various modifications may be made thereto.
- the plasmon generator may have the same configuration as that of the plasmon generator 34 of the second embodiment.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- Recording Or Reproducing By Magnetic Means (AREA)
- Magnetic Heads (AREA)
Abstract
An outer surface of a plasmon generator includes: a plasmon exciting part that faces an evanescent light generating surface with a predetermined distance therebetween; and a front end face located in a medium facing surface. The plasmon generator has: first and second sidewall parts that are connected to the plasmon exciting part and increase in distance from each other with increasing distance from the plasmon exciting part; and at least one extended portion connected to an edge of at least one of the first and second sidewall parts opposite from the plasmon exciting part. A magnetic pole has a portion interposed between the first and second sidewall parts. The front end face includes first and second portions lying at ends of the first and second sidewall parts and connected to each other into a V-shape. An end face of the magnetic pole has a portion interposed between the first and second portions of the front end face.
Description
- 1. Field of the Invention
- The present invention relates to a thermally-assisted magnetic recording head including a plasmon generator for use in thermally-assisted magnetic recording where a magnetic recording medium is irradiated with near-field light to lower the coercivity of the magnetic recording medium for data writing.
- 2. Description of the Related Art
- Recently, magnetic recording devices such as magnetic disk drives have been improved in recording density, and thin-film magnetic heads and magnetic recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a read head including a magnetoresistive element (hereinafter, also referred to as MR element) intended for reading and a write head including an induction-type electromagnetic transducer intended for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the magnetic recording medium.
- Magnetic recording media are discrete media each made of an aggregate of magnetic fine particles, each magnetic fine particle forming a single-domain structure. A single recording bit of a magnetic recording medium is composed of a plurality of magnetic fine particles. For improved recording density, it is necessary to reduce asperities at the borders between adjoining recording bits. To achieve this, the magnetic fine particles must be made smaller. However, making the magnetic fine particles smaller causes the problem that the thermal stability of magnetization of the magnetic fine particles decreases with decreasing volume of the magnetic fine particles. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the magnetic recording medium, and this makes it difficult to perform data writing with existing magnetic heads.
- To solve the foregoing problems, there has been proposed a technique so-called thermally-assisted magnetic recording. This technique uses a magnetic recording medium having high coercivity. When writing data, a magnetic field and heat are simultaneously applied to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. Hereinafter, a magnetic head for use in thermally-assisted magnetic recording will be referred to as a thermally-assisted magnetic recording head.
- In thermally-assisted magnetic recording, near-field light is typically used as a means for applying heat to the magnetic recording medium. A commonly known method for generating near-field light is to use a near-field optical probe or so-called plasmon antenna, which is a piece of metal that generates near-field light from plasmons excited by irradiation with light.
- However, the plasmon antenna which generates near-field light by direct irradiation with light is known to exhibit very low efficiency of transformation of the applied light into near-field light. The energy of the light applied to the plasmon antenna is mostly reflected off the surface of the plasmon antenna, or transformed into thermal energy and absorbed by the plasmon antenna. The plasmon antenna is small in volume since the size of the plasmon antenna is set to be smaller than or equal to the wavelength of the light. The plasmon antenna therefore shows a significant increase in temperature when it absorbs the thermal energy.
- Such a temperature increase makes the plasmon antenna expand in volume and protrude from a medium facing surface, which is the surface of the thermally-assisted magnetic recording head to face the magnetic recording medium. This causes an end of the read head located in the medium facing surface to get farther from the magnetic recording medium, thereby causing the problem that a servo signal cannot be read during write operations.
- There has been known a technique in which a dielectric and a metal are arranged to face each other with a predetermined gap therebetween, and surface plasmons are excited on the metal by utilizing evanescent light that results from the total reflection of the light propagated through the dielectric at the surface of the dielectric. As a related technique, U.S. Pat. No. 7,454,095 discloses a technique in which a metal waveguide and a dielectric waveguide are arranged to face each other with a predetermined gap therebetween, and the metal waveguide is coupled with the dielectric waveguide in a surface plasmon mode. It is then conceivable to establish coupling between the light propagated through the waveguide's core and a plasmon generator, a piece of metal, in a surface plasmon mode through a buffer part so that surface plasmons are excited on the plasmon generator, instead of directly irradiating the plasmon generator with the light. According to such a technique, it is possible to transform the light propagated through the core into near-field light with high efficiency. Since the plasmon generator is not directly irradiated with the light propagated through the core, it is also possible to prevent the plasmon generator from excessively increasing in temperature.
- Using the foregoing technique, part of the energy of the light propagated through the core is transformed into heat in the plasmon generator, and the plasmon generator rises in temperature. Even with the foregoing technique, it is therefore desired to develop a technology that can further suppress a rise in temperature of the plasmon generator.
- For thermally-assisted magnetic recording, it is desired that the position of occurrence of the write magnetic field and the position of occurrence of the near-field light be located as close as possible in the medium facing surface. U.S. Patent Application Publication No. 2007/139818 A1 discloses a magnetic head in which a near-field light generating part, which generates near-field light when irradiated with laser light; and an end of a main magnetic pole layer are arranged to overlap each other directly or through a dielectric layer in the medium facing surface. U.S. Patent Application Publication No. 2009/168220 A1 discloses a magnetic head in which at least a part of a main magnetic pole is interposed between first and second near-field light generating parts, each of which generates near-field light when irradiated with laser light.
- The magnetic head disclosed in U.S. Patent Application Publication No. 2007/139818 A1 and the magnetic head disclosed in U.S. Patent Application Publication No. 2009/168220 A1 both make it possible to locate the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other, but neither can suppress a rise in temperature of the near-field light generating part since the near-field light generating part is directly irradiated with light.
- When a thermally-assisted magnetic recording head employs such a configuration that the light propagated through the core is coupled with the plasmon generator in a surface plasmon mode through a buffer part, there arises the following problem if the position of occurrence of the write magnetic field and the position of occurrence of the near-field light are located close to each other. That is, in such a case, both the core and the magnetic pole need to be located near the plasmon generator. It follows that the magnetic pole is located near the core. The magnetic pole is typically made of a magnetic metal material. The presence of such a magnetic pole near the core causes the problem that part of the light propagated through the core is absorbed by the magnetic pole and the use efficiency of the light propagated through the core thereby decreases.
- It is an object of the present invention to provide a thermally-assisted magnetic recording head that allows efficient use of the light propagated through the core of the waveguide, allows the position of occurrence of the write magnetic field and the position of the occurrence of the near-field light to be close to each other, and allows suppression of a temperature rise of the plasmon generator, and to provide a head gimbal assembly and a magnetic recording device that each include such a thermally-assisted magnetic recording head.
- A thermally-assisted magnetic recording head of the present invention includes: a medium facing surface that faces a magnetic recording medium; a magnetic pole that has an end face located in the medium facing surface and produces a write magnetic field for writing data on the magnetic recording medium; a waveguide including a core and a clad, the core propagating light; and a plasmon generator. The core has an evanescent light generating surface that generates evanescent light based on the light propagated through the core. The plasmon generator has an outer surface, the outer surface including: a plasmon exciting part that faces the evanescent light generating surface with a predetermined distance therebetween; and a front end face located in the medium facing surface.
- The plasmon generator has: a first sidewall part and a second sidewall part that are each connected to the plasmon exciting part, the first and second sidewall parts increasing in distance from each other with increasing distance from the plasmon exciting part; and at least one extended portion that is connected to an edge of at least one of the first and second sidewall parts, the edge being opposite from the plasmon exciting part. From the edge of the at least one of the first and second sidewall parts opposite from the plasmon exciting part, the at least one extended portion extends parallel to the evanescent light generating surface and away from both the first and second sidewall parts. The magnetic pole has a portion interposed between the first and second sidewall parts.
- The front end face includes: a first portion and a second portion that lie at respective ends of the first and second sidewall parts and are connected to each other into a V-shape; at least one third portion that lies at an end of the at least one extended portion; and a near-field light generating edge that lies at an end of the plasmon exciting part. The end face of the magnetic pole has a portion interposed between the first and second portions of the front end face.
- A surface plasmon is excited on the plasmon exciting part through coupling with the evanescent light generated from the evanescent light generating surface. The near-field light generating edge generates near-field light based on the surface plasmon excited on the plasmon exciting part.
- In the thermally-assisted magnetic recording head of the present invention, the at least one extended portion of the plasmon generator has a heat sink function of dissipating heat from the plasmon generator to outside.
- In the thermally-assisted magnetic recording head of the present invention, the magnetic pole may be in contact with the plasmon generator.
- In the thermally-assisted magnetic recording head of the present invention, the first and second sidewall parts may be connected to each other so that the connected first and second sidewall parts have a V-shaped cross section parallel to the medium facing surface. In such a case, the plasmon exciting part may include a propagative edge that lies at an end of the connected first and second sidewall parts closer to the evanescent light generating surface. The near-field light generating edge may lie at an end of the propagative edge.
- In the thermally-assisted magnetic recording head of the present invention, the plasmon generator may further have a bottom part that is shaped like a plate and connects the first and second sidewall parts to each other at their respective edges closer to the evanescent light generating surface. In such a case, the plasmon exciting part may include a flat surface part that is formed by a surface of the bottom part that is closer to the evanescent light generating surface. The flat surface part may include a width changing portion. The width changing portion may have a width that decreases with decreasing distance to the medium facing surface, the width being in a direction parallel to the medium facing surface and the evanescent light generating surface.
- The thermally-assisted magnetic recording head of the present invention may further include a buffer part that is located between the evanescent light generating surface and the plasmon exciting part and has a refractive index lower than that of the core.
- In the thermally-assisted magnetic recording head of the present invention, a dimension of the first and second sidewall parts in a direction perpendicular to the evanescent light generating surface may fall within a range of 200 to 400 nm.
- In the thermally-assisted magnetic recording head of the present invention, a dimension of the front end face on a virtual straight line that passes through the near-field light generating edge and extends in the direction perpendicular to the evanescent light generating surface may fall within a range of 20 to 70 nm.
- The thermally-assisted magnetic recording head of the present invention may further include a conductor made of a conductive material, the conductor having a Seebeck coefficient different from that of the plasmon generator and being in contact with the plasmon generator. In such a case, heat absorption by the Peltier effect occurs in a contact area between the plasmon generator and the conductor when a current is made to flow from one of the plasmon generator and the conductor, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area. In such a case, the plasmon generator may be made of Au, and the conductive material may contain at least one of Co, Ni, and a CuNi alloy.
- When the thermally-assisted magnetic recording head of the present invention includes the above-mentioned conductor, the conductor may be in contact with the plasmon generator at least on a virtual straight line that passes through the near-field light generating edge and extends in the direction perpendicular to the evanescent light generating surface. In such a case, a dimension of the conductor on the virtual straight line may fall within a range of 20 to 50 nm. At least part of the conductor may be interposed between the plasmon generator and the magnetic pole.
- The thermally-assisted magnetic recording head of the present invention may further include a first electrode that is electrically connected to the plasmon generator and a second electrode that is electrically connected to the conductor. A voltage for generating a current may be applied to the first and second electrodes. Alternatively, the conductor may be electrically connected to the magnetic pole, and a voltage for generating a current may be applied to the plasmon generator and the magnetic pole.
- A head gimbal assembly of the present invention includes: the thermally-assisted magnetic recording head of the present invention; and a suspension that supports the thermally-assisted magnetic recording head. A magnetic recording device of the present invention includes: a magnetic recording medium; the thermally-assisted magnetic recording head of the present invention; and a positioning device that supports the thermally-assisted magnetic recording head and positions the same with respect to the magnetic recording medium.
- According to the thermally-assisted magnetic recording head, the head gimbal assembly and the magnetic recording device of the present invention, a surface plasmon is excited on the plasmon exciting part of the plasmon generator through coupling with the evanescent light generated from the evanescent light generating surface of the core of the waveguide. The near-field light generating part generates near-field light based on the surface plasmon. According to the present invention, it is thereby possible to transform the light propagated through the core into near-field light with high efficiency.
- In the present invention, the front end face of the plasmon generator has the first and second portions that are connected to each other into a V-shape, and the near-field light generating edge lying at an end of the plasmon exciting part. The end face of the magnetic pole has the portion interposed between the first and second portions of the front end face. Consequently, according to the present invention, it is possible to locate the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other.
- In the present invention, the plasmon generator has at least one extended portion having the heat sink function as described above. Consequently, according to the present invention, it is possible to suppress a rise in temperature of the plasmon generator.
- In the present invention, the thermally-assisted magnetic recording head may include a conductor made of a conductive material, the conductor having a Seebeck coefficient different from that of the plasmon generator and being in contact with the plasmon generator. In such a case, it is possible to cool the plasmon generator by the Peltier effect and further suppress a rise in temperature of the plasmon generator.
- Other and further objects, features and advantages of the present invention will appear more fully from the following description.
-
FIG. 1 is a perspective view showing a waveguide's core, a plasmon generator, and a magnetic pole of a thermally-assisted magnetic recording head according to a first embodiment of the invention. -
FIG. 2 is a front view showing a part of the medium facing surface of a head unit of the thermally-assisted magnetic recording head according to the first embodiment of the invention. -
FIG. 3 is a cross-sectional view showing the core, the plasmon generator, and the magnetic pole of the thermally-assisted magnetic recording head according to the first embodiment of the invention. -
FIG. 4 is a perspective view showing the main part of the heat unit of a magnetic recording device according to the first embodiment of the invention. -
FIG. 5 is a perspective view showing the magnetic recording device according to the first embodiment of the invention. -
FIG. 6 is a perspective view showing a head gimbal assembly according to the first embodiment of the invention. -
FIG. 7 is a perspective view showing the thermally-assisted magnetic recording head according to the first embodiment of the invention. -
FIG. 8 shows a cross section taken along line 8-8 ofFIG. 7 . -
FIG. 9 is a plan view showing a part of the head unit of the thermally-assisted magnetic recording head according to the first embodiment of the invention. -
FIG. 10 is a block diagram showing the circuit configuration of the magnetic recording device according to the first embodiment of the invention. -
FIG. 11 is a cross-sectional view showing a step of a method of forming the plasmon generator and the magnetic pole of the first embodiment of the invention. -
FIG. 12 is a cross-sectional view showing a step that follows the step shown inFIG. 11 . -
FIG. 13 is a cross-sectional view showing a step that follows the step shown inFIG. 12 . -
FIG. 14 is a cross-sectional view showing a step that follows the step shown inFIG. 13 . -
FIG. 15 is a cross-sectional view showing a step that follows the step shown inFIG. 14 . -
FIG. 16 is a front view showing a core, a plasmon generator, and a magnetic pole in a medium facing surface of a model of a first type used in a second simulation. -
FIG. 17 is a front view showing a core, a plasmon generator, and a magnetic pole in a medium facing surface of a model of a second type used in the second simulation. -
FIG. 18 is a characteristic chart showing the effective write magnetic field determined by the second simulation. -
FIG. 19 is a characteristic chart showing the near-field light intensity determined by a third simulation. -
FIG. 20 is a perspective view showing a waveguide's core, a plasmon generator, and a magnetic pole of a thermally-assisted magnetic recording head according to a second embodiment of the invention. -
FIG. 21 is a plan view showing a plasmon exciting part of the plasmon generator shown inFIG. 20 . -
FIG. 22 is a front view showing a part of the medium facing surface of a head unit of a thermally-assisted magnetic recording head according to a third embodiment of the invention. -
FIG. 23 is a cross-sectional view showing a waveguide's core, a plasmon generator, and a magnetic pole of the thermally-assisted magnetic recording head according to the third embodiment of the invention. -
FIG. 24A andFIG. 24B are explanatory diagrams showing a step of a method of forming the plasmon generator, the magnetic pole, and the conductor of the third embodiment of the invention. -
FIG. 25A andFIG. 25B are explanatory diagrams showing a step that follows the step shown inFIG. 24A andFIG. 24B . -
FIG. 26A andFIG. 26B are explanatory diagrams showing a step that follows the step shown inFIG. 25A andFIG. 25B . -
FIG. 27 is a cross-sectional view showing a step that follows the step shown inFIG. 26A andFIG. 26B . -
FIG. 28 is a cross-sectional view showing a step that follows the step shown inFIG. 27 . -
FIG. 29 is a cross-sectional view showing a step that follows the step shown inFIG. 28 . -
FIG. 30 is a front view showing a part of the medium facing surface of a head unit of a thermally-assisted magnetic recording head according to a fourth embodiment of the invention. - Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, reference is made to
FIG. 5 to describe a magnetic disk drive that functions as a magnetic recording device according to a first embodiment of the invention. As shown inFIG. 5 , the magnetic disk drive includes a plurality ofmagnetic disks 201 as a plurality of magnetic recording media, and aspindle motor 202 for rotating the plurality ofmagnetic disks 201. Themagnetic disks 201 of the present embodiment are for use in perpendicular magnetic recording. Themagnetic disks 201 each have such a structure that a soft magnetic backing layer, a middle layer, and a magnetic recording layer (perpendicular magnetization layer) are stacked in this order on a disk substrate. - The magnetic disk drive further includes an
assembly carriage device 210 having a plurality of drivingarms 211, and a plurality ofhead gimbal assemblies 212 attached to respective distal ends of the drivingarms 211. Thehead gimbal assemblies 212 each include a thermally-assistedmagnetic recording head 1 according to the present embodiment, and asuspension 220 that supports the thermally-assistedmagnetic recording head 1. - The
assembly carriage device 210 is a device for positioning the thermally-assisted magnetic recording heads 1 on tracks that are formed in the magnetic recording layers of themagnetic disks 201 and that have recording bits aligned thereon. Theassembly carriage device 210 further has apivot bearing shaft 213 and avoice coil motor 214. The plurality of drivingarms 211 are stacked in a direction along thepivot bearing shaft 213 and are pivotable about theshaft 213 by being driven by thevoice coil motor 214. The magnetic recording device of the present invention is not structurally limited to the magnetic disk drive having the above-described configuration. For example, the magnetic recording device of the present invention may be provided with a singlemagnetic disk 201, asingle driving arm 211, a singlehead gimbal assembly 212 and a single thermally-assistedmagnetic recording head 1. - The magnetic disk drive further includes a
control circuit 230 that controls the read/write operations of the thermally-assisted magnetic recording heads 1 and also controls the light emitting operation of a laser diode serving as a light source for generating laser light for thermally-assisted magnetic recording described later. -
FIG. 6 is a perspective view showing thehead gimbal assembly 212 ofFIG. 5 . As previously described, thehead gimbal assembly 212 includes the thermally-assistedmagnetic recording head 1 and thesuspension 220. Thesuspension 220 has aload beam 221, aflexure 222 fixed to theload beam 221 and having flexibility, abase plate 223 provided at the base part of theload beam 221, and awiring member 224 provided on theload beam 221 and theflexure 222. Thewiring member 224 includes a plurality of leads. The thermally-assistedmagnetic recording head 1 is fixed to theflexture 222 at the distal end of thesuspension 220 such that thehead 1 faces the surface of themagnetic disk 201 with a predetermined spacing (flying height). One end of thewiring member 224 is electrically connected to a plurality of terminals of the thermally-assistedmagnetic recording head 1. The other end of thewiring member 224 is provided with a plurality of pad-shaped terminals arranged at the base part of theload beam 221. - The
assembly carriage device 210 and thesuspension 220 correspond to the positioning device of the present invention. The head gimbal assembly of the present invention is not limited to the one having the configuration shown inFIG. 6 . For example, the head gimbal assembly of the present invention may have an IC chip for driving the head that is mounted somewhere along thesuspension 220. - The configuration of the thermally-assisted
magnetic recording head 1 according to the present embodiment will now be described with reference toFIG. 7 toFIG. 9 .FIG. 7 is a perspective view showing the thermally-assistedmagnetic recording head 1.FIG. 8 shows a cross section taken along line 8-8 ofFIG. 7 .FIG. 9 is a plan view showing a part of a head unit of the thermally-assisted magnetic recording head. The thermally-assistedmagnetic recording head 1 includes aslider 10 and alight source unit 50.FIG. 8 shows the state where theslider 10 and thelight source unit 50 are separated from each other. - The
slider 10 includes aslider substrate 11 and ahead unit 12. Theslider substrate 11 is rectangular-solid-shaped and is made of a ceramic material such as aluminum oxide-titanium carbide (Al2O3—TiC) Theslider substrate 11 has amedium facing surface 11 a that faces themagnetic disk 201, arear surface 11 b on the opposite side from themedium facing surface 11 a, and four surfaces that connect themedium facing surface 11 a to therear surface 11 b. One of the four surfaces that connect themedium facing surface 11 a to therear surface 11 b is an element-formingsurface 11 c. The element-formingsurface 11 c is perpendicular to themedium facing surface 11 a. Thehead unit 12 is disposed on the element-formingsurface 11 c. Themedium facing surface 11 a is processed so as to obtain an appropriate flying height of theslider 10 with respect to themagnetic disk 201. Thehead unit 12 has amedium facing surface 12 a that faces themagnetic disk 201, and arear surface 12 b on the opposite side from themedium facing surface 12 a. Themedium facing surface 12 a is parallel to themedium facing surface 11 a of theslider substrate 11. - Where the components of the
head unit 12 are concerned, with respect to a reference position, a position located in a direction that extends perpendicular to the element-formingsurface 11 c and away from the element-formingsurface 11 c is defined as “above”, and a position located in a direction opposite to the above-mentioned direction is defined as “below”. Where the layers included in thehead unit 12 are concerned, the surface closer to the element-formingsurface 11 c is defined as a “bottom surface,” and the surface farther from the element-formingsurface 11 c as a “top surface.” - Moreover, X direction, Y direction, Z direction, −X direction, −Y direction, and −Z direction will be defined as follows. The X direction is a direction perpendicular to the
medium facing surface 11 a and from themedium facing surface 11 a to the rear surface lib. The Y direction is a direction parallel to themedium facing surface 11 a and the element-formingsurface 11 c and from the back side to the front side ofFIG. 8 . The Z direction is a direction that extends perpendicular to the element-formingsurface 11 c and away from the element-formingsurface 11 c. The −X direction, the −Y direction, and the −Z direction are opposite to the X direction, the Y direction, and the Z direction, respectively. As viewed from theslider 10, themagnetic disk 201 moves in the Z direction. Theslider 10 has an air inflow end (a leading end) at the end of themedium facing surface 11 a in the −Z direction. Theslider 10 has an air outflow end (a trailing end) at the end of themedium facing surface 12 a in the Z direction. Track width direction TW is a direction parallel to the Y direction. - The
light source unit 50 includes alaser diode 60 serving as a light source for emitting laser light, and asupport member 51 that is shaped like a rectangular solid and supports thelaser diode 60. Thesupport member 51 is made of, for example, a ceramic material such as aluminum oxide-titanium carbide (Al2O3—TiC). Thesupport member 51 has abonding surface 51 a, arear surface 51 b on the opposite side from thebonding surface 51 a, and four surfaces that connect thebonding surface 51 a to therear surface 51 b. One of the four surfaces that connect thebonding surface 51 a to therear surface 51 b is a light-source-mountingsurface 51 c. Thebonding surface 51 a is the surface to be bonded to therear surface 11 b of theslider substrate 11. The light-source-mountingsurface 51 c is perpendicular to thebonding surface 51 a and parallel to the element-formingsurface 11 c. Thelaser diode 60 is mounted on the light-source-mountingsurface 51 c. Thesupport member 51 may have a heat sink function of dissipating heat generated by thelaser diode 60, in addition to the function of supporting thelaser diode 60. - As shown in
FIG. 8 , thehead unit 12 includes an insulatinglayer 13 disposed on the element-formingsurface 11 c, and also includes a readhead 14, awrite head 16, and aprotection layer 17 that are stacked in this order on the insulatinglayer 13. The insulatinglayer 13 and theprotection layer 17 are each made of an insulating material such as Al2O3 (hereinafter, also referred to as alumina). - The read
head 14 includes: abottom shield layer 21 disposed on the insulatinglayer 13; anMR element 22 disposed on thebottom shield layer 21; atop shield layer 23 disposed on theMR element 22; and an insulatinglayer 24 disposed between thebottom shield layer 21 and thetop shield layer 23 around theMR element 22. Thebottom shield layer 21 and thetop shield layer 23 are each made of a soft magnetic material. The insulatinglayer 24 is made of an insulating material such as alumina. - An end of the
MR element 22 is located in themedium facing surface 12 a. The MR element may be a giant magnetoresistive (GMR) element or a tunneling magnetoresistive (TMR) element, for example. The GMR element may be of either the current-in-plane (CIP) type in which a sense current for use in magnetic signal detection is fed in a direction nearly parallel to the plane of layers constituting the GMR element or the current-perpendicular-to-plane (CPP) type in which the sense current is fed in a direction nearly perpendicular to the plane of layers constituting the GMR element. If theMR element 22 is a TMR element or a CPP-type GMR element, thebottom shield layer 21 and thetop shield layer 23 may also function as electrodes for feeding the sense current to theMR element 22. If theMR element 22 is a CIP-type GMR element, insulating films are respectively provided between theMR element 22 and thebottom shield layer 21 and between theMR element 22 and thetop shield layer 23, and two leads are provided between these insulating films in order to feed the sense current to theMR element 22. - The
head unit 12 further includes an insulatinglayer 25 disposed on thetop shield layer 23, amiddle shield layer 26 disposed on the insulatinglayer 25, and an insulatinglayer 27 disposed on themiddle shield layer 26. Themiddle shield layer 26 has the function of shielding theMR element 22 from a magnetic field produced in thewrite head 16. The insulating layers 25 and 27 are each made of an insulating material such as alumina. Themiddle shield layer 26 is made of a soft magnetic material. The insulatinglayer 25 and themiddle shield layer 26 may be omitted. - The
write head 16 of the present embodiment is for use in perpendicular magnetic recording. Thewrite head 16 includes abottom yoke layer 28 disposed on the insulatinglayer 27, abottom shield layer 29 disposed on thebottom yoke layer 28 in the vicinity of themedium facing surface 12 a, acoupling layer 42A disposed on thebottom yoke layer 28 at a position away from themedium facing surface 12 a, and an insulatinglayer 30 disposed around thebottom yoke layer 28, thebottom shield layer 29 and thecoupling layer 42A. Thebottom yoke layer 28, thebottom shield layer 29, and thecoupling layer 42A are each made of a soft magnetic material. The insulatinglayer 30 is made of an insulating material such as alumina. - The
write head 16 further includes a waveguide that includes acore 32 and a clad. The clad includes a cladlayer 31 and aclad layer 33. Theclad layer 31 is disposed over thebottom shield layer 29, the insulatinglayer 30 and thecoupling layer 42A. Thecore 32 is disposed on the cladlayer 31. Theclad layer 33 covers the cladlayer 31 and thecore 32. Thecore 32 extends in a direction perpendicular to themedium facing surface 12 a (X direction). Thecore 32 has anincident end 32 a, an end face closer to themedium facing surface 12 a, a top surface, a bottom surface, and two side surfaces. The end face of the core 32 may be located in themedium facing surface 12 a or away from themedium facing surface 12 a.FIG. 8 shows an example where the end face of thecore 32 is located in themedium facing surface 12 a. Thecore 32 propagates laser light that is emitted from thelaser diode 60 and incident on the incident end 32 a. - The
core 32 is made of a dielectric material that transmits the laser light. Each of theclad layers core 32. For example, if the laser light has a wavelength of 600 nm and thecore 32 is made of Al2O3 (refractive index n=1.63), theclad layers core 32 is made of tantalum oxide such as Ta2O5 (n=2.16), theclad layers - The
write head 16 further includes aplasmon generator 34 disposed above the core 32 in the vicinity of themedium facing surface 12 a, and amagnetic pole 35 disposed at such a position that theplasmon generator 34 is interposed between themagnetic pole 35 and thecore 32. Themagnetic pole 35 has a top surface that is located at a level higher than the top surface of the cladlayer 33. Theplasmon generator 34 is made of a conductive material such as metal. For example, theplasmon generator 34 may be made of one element selected from the group consisting of Pd, Pt, Rh, Ir, Ru, Au, Ag, Cu, and Al, or of an alloy composed of two or more of these elements. Themagnetic pole 35 is made of a soft magnetic material, or a magnetic metal material in particular.FIG. 9 shows an example of the length of themagnetic pole 35 in the X direction. In this example, themagnetic pole 35 has a length of 3 μm in the X direction. The shapes and locations of the core 32, theplasmon generator 34 and themagnetic pole 35 will be detailed later. - The
write head 16 further includes acoupling layer 42C at a position away from themedium facing surface 12 a. A part of thecoupling layer 42C is embedded in the cladlayer 33. Thecoupling layer 42C is located above thecoupling layer 42A. Thecoupling layer 42C has a top surface at a level higher than the top surface of the cladlayer 33. Thecoupling layer 42C is made of a soft magnetic material. - As shown in
FIG. 9 , thewrite head 16 further includes two coupling portions 42B1 and 42B2 embedded in theclad layers core 32. The bottom surfaces of the coupling portions 42B1 and 42B2 are in contact with the top surface of thecoupling layer 42A. The top surfaces of the coupling portions 42B1 and 42B2 are in contact with the bottom surface of thecoupling layer 42C. - The
write head 16 further includes an insulatinglayer 37 disposed around themagnetic pole 35 and thecoupling layer 42C on the cladlayer 33, an insulatinglayer 38 disposed on the insulatinglayer 37, acoupling layer 36 disposed on themagnetic pole 35, and acoupling layer 42D disposed on thecoupling layer 42C. Thecoupling layer 36 has an end face that is closer to themedium facing surface 12 a, the end face being located at a distance from themedium facing surface 12 a. - The
write head 16 further includes a plurality offirst coil elements 40A disposed on the insulatinglayer 38, and an insulatinglayer 39 disposed around the coupling layers 36 and 42D and thefirst coil elements 40A. Thefirst coil elements 40A are arranged to align in the X direction. Although not shown, thefirst coil elements 40A each have a main part that extends in the track width direction TW (Y direction). Thefirst coil elements 40A are each made of a conductive material such as copper. The coupling layers 36 and 42D are each made of a soft magnetic material. The insulating layers 37, 38, and 39 are each made of an insulating material such as alumina. - The
write head 16 further includes an insulatinglayer 41 disposed to cover thefirst coil elements 40A, atop yoke layer 43 disposed over the coupling layers 36 and 42D and the insulatinglayer 41, and an insulatinglayer 44 disposed around thetop yoke layer 43. Thetop yoke layer 43 is in contact with the top surface of thecoupling layer 36 at a position near themedium facing surface 12 a, and in contact with the top surface of thecoupling layer 42D at a position away from themedium facing surface 12 a.FIG. 9 shows an example of the dimensions of thetop yoke layer 43 in the X direction and in the track width direction TW (Y direction). In this example, thetop yoke layer 43 has a dimension of 12 μm in the X direction and a dimension of 17 μm in the track width direction TW (Y direction). Thetop yoke layer 43 is made of a soft magnetic material. The insulating layers 41 and 44 are each made of an insulating material such as alumina. - The
write head 16 further includes an insulatinglayer 45 disposed over thetop yoke layer 43 and the insulatinglayer 44, and a plurality ofsecond coil elements 40B disposed on the insulatinglayer 45. The insulatinglayer 45 is made of an insulating material such as alumina. -
FIG. 9 shows thesecond coil elements 40B. Thesecond coil elements 40B are arranged to align in the X direction. Thesecond coil elements 40B each have a main part that extends in the track width direction TW (Y direction). Thesecond coil elements 40B are each made of a conductive material such as copper. - Although not shown, the thermally-assisted
magnetic recording head 1 further includes a plurality of connecting portions. The plurality of connecting portions connect the plurality offirst coil elements 40A to the plurality ofsecond coil elements 40B so as to form acoil 40 wound around thetop yoke layer 43 helically. The plurality of connecting portions are provided to penetrate the insulatinglayers - In the
write head 16, thebottom shield layer 29, thebottom yoke layer 28, thecoupling layer 42A, the coupling portions 42B1 and 42B2, the coupling layers 42C and 42D, thetop yoke layer 43, thecoupling layer 36, and themagnetic pole 35 form a magnetic path for passing a magnetic flux corresponding to the magnetic field produced by thecoil 40. Themagnetic pole 35 has an end face located in themedium facing surface 12 a, allows the magnetic flux corresponding to the magnetic field produced by thecoil 40 to pass, and produces a write magnetic field for writing data on themagnetic disk 201 by means of the perpendicular magnetic recording system. Thebottom shield layer 29 takes in a magnetic flux that is generated from the end face of themagnetic pole 35 and that expands in directions other than the direction perpendicular to the plane of themagnetic disk 201, and thereby prevents the magnetic flux from reaching themagnetic disk 201. - As shown in
FIG. 8 , theprotection layer 17 is disposed to cover thewrite head 16. As shown inFIG. 7 , thehead unit 12 further includes a pair ofterminals 18 that are disposed on the top surface of theprotection layer 17 and electrically connected to theMR element 22, and another pair ofterminals 19 that are disposed on the top surface of theprotection layer 17 and electrically connected to thecoil 40. Theseterminals wiring member 224 shown inFIG. 6 . - The
laser diode 60 may be a laser diode of InP type, GaAs type, GaN type or the like that is commonly used for such applications as communications, optical disc storage and material analysis. Thelaser diode 60 may emit laser light of any wavelength within the range of, for example, 375 nm to 1.7 μm. Specifically, thelaser diode 60 may be an InGaAsP/InP quarternary mixed crystal laser diode having an emittable wavelength range of 1.2 to 1.67 μm, for example. - As shown in
FIG. 8 , thelaser diode 60 has a multilayer structure including alower electrode 61, anactive layer 62, and anupper electrode 63. A reflectinglayer 64 made of, for example, SiO2 or Al2O3, is formed on two cleavage planes of the multilayer structure so as to excite oscillation by total reflection of light. The reflectinglayer 64 has an opening for emitting laser light in the position of theactive layer 62 including anemission center 62 a. Thelaser diode 60 has a thickness TLA of around 60 to 200 μm, for example. - The
light source unit 50 further includes a terminal 52 disposed on the light-source-mountingsurface 51 c and electrically connected to thelower electrode 61, and a terminal 53 disposed on the light-source-mountingsurface 51 c and electrically connected to theupper electrode 63. Theseterminals wiring member 224 shown inFIG. 6 . When a predetermined voltage is applied to thelaser diode 60 through theterminals emission center 62 a of thelaser diode 60. The laser light to be emitted from thelaser diode 60 is preferably TM-mode polarized light whose electric field oscillates in a direction perpendicular to the plane of theactive layer 62. - The
laser diode 60 can be driven by a power supply inside the magnetic disk drive. The magnetic disk drive usually includes a power supply that generates a voltage of 2 V or so, for example. This supply voltage is sufficient to drive thelaser diode 60. Thelaser diode 60 has a power consumption of, for example, several tens of milliwatts or so, which can be adequately covered by the power supply in the magnetic disk drive. - The
light source unit 50 is fixed to theslider 10 by bonding thebonding surface 51 a of thesupport member 51 to therear surface 11 b of theslider substrate 11, as shown inFIG. 8 . Thelaser diode 60 and the core 32 are positioned so that the laser light emitted from thelaser diode 60 will be incident on the incident end 32 a of thecore 32. - The shapes and locations of the core 32, the
plasmon generator 34, and themagnetic pole 35 will now be described in detail with reference toFIG. 1 toFIG. 4 .FIG. 1 is a perspective view showing thecore 32, theplasmon generator 34, and themagnetic pole 35.FIG. 2 is a front view showing a part of themedium facing surface 12 a of thehead unit 12.FIG. 3 is a cross-sectional view showing thecore 32, theplasmon generator 34, and themagnetic pole 35.FIG. 4 is a perspective view showing the main part of theheat unit 12. Note thatFIG. 1 illustrates an exploded view of theplasmon generator 34 and themagnetic pole 35. - Aside from the incident end 32 a shown in
FIG. 8 , the core 32 further has: anend face 32 b that is closer to themedium facing surface 12 a; an evanescentlight generating surface 32 c, which is a top surface; abottom surface 32 d; and twoside surfaces FIG. 1 . The evanescentlight generating surface 32 c generates evanescent light based on the light propagated through thecore 32. WhileFIG. 1 toFIG. 3 show an example where theend face 32 b is located in themedium facing surface 12 a, theend face 32 b may be located away from themedium facing surface 12 a. - As shown in
FIG. 2 , the cladlayer 33 has atop surface 33 a located above thecore 32, and agroove 33 b that opens in thetop surface 33 a and is located above thecore 32. Thegroove 33 b extends in the direction perpendicular to themedium facing surface 12 a (X direction). Thegroove 33 b is V-shaped in cross section parallel to themedium facing surface 12 a. - As shown in
FIG. 1 toFIG. 3 , theplasmon generator 34 has an outer surface that includes a plasmonexciting part 341 and afront end face 342. The plasmonexciting part 341 faces the evanescentlight generating surface 32 c of the core 32 with a predetermined distance therebetween. Thefront end face 342 is located in themedium facing surface 12 a. Surface plasmons are excited on the plasmonexciting part 341 through coupling with the evanescent light generated from the evanescentlight generating surface 32 c. As shown inFIG. 3 , the cladlayer 33 has a part interposed between the evanescentlight generating surface 32 c and the plasmonexciting part 341, the part of the cladlayer 33 forming abuffer part 33A that has a refractive index lower than that of thecore 32. - As shown in
FIG. 1 andFIG. 2 , theplasmon generator 34 has a V-shapedportion 34A that has an end face located in themedium facing surface 12 a. The V-shapedportion 34A extends in the direction perpendicular to themedium facing surface 12 a (X direction). Thegroove 33 b mentioned above is to accommodate the V-shapedportion 34A. - The V-shaped
portion 34A has a first sidewall part 34A1 and a second sidewall part 34A2 that are each connected to the plasmonexciting part 341, and that increase in distance from each other with increasing distance from the plasmonexciting part 341. The first and second sidewall parts 34A1 and 34A2 are each shaped like a plate. The first and second sidewall parts 34A1 and 34A2 are connected to each other so that the connected first and second sidewall parts 34A1 and 34A2 have a V-shaped cross section parallel to themedium facing surface 12 a. - The
plasmon generator 34 further has at least one extended portion that is connected to an edge of at least one of the first and second sidewall parts 34A1 and 34A2, the edge being opposite from the plasmonexciting part 341. In the present embodiment, theplasmon generator 34 has an extendedportion 34B that is connected to the edge of the first sidewall part 34A1 opposite from the plasmonexciting part 341, and anextended portion 34C that is connected to the edge of the second sidewall part 34A2 opposite from the plasmonexciting part 341. From the edge of the first sidewall part 34A1 opposite from the plasmonexciting part 341, theextended portion 34B extends parallel to the evanescentlight generating surface 32 c and away from both the first and second sidewall parts 34A1 and 34A2 (−Y direction). From the edge of the second sidewall part 34A2 opposite from the plasmonexciting part 341, theextended portion 34C extends parallel to the evanescentlight generating surface 32 c and away from both the first and second sidewall parts 34A1 and 34A2 (Y direction). As viewed from above, the outer edges of theextended portions magnetic pole 35. - The plasmon
exciting part 341 has apropagative edge 341 a that lies at an end of the connected first and second sidewall parts 34A1 and 34A2 closer to the evanescentlight generating surface 32 c. In the example shown inFIG. 3 , the entire plasmonexciting part 341 is composed of thepropagative edge 341 a. As will be described later, thepropagative edge 341 a propagates plasmons. In a cross section parallel to themedium facing surface 12 a, thepropagative edge 341 a may have the shape of a perfectly pointed edge whereas it may have an arc shape in a microscopic view. - The
front end face 342 has afirst portion 342 a and asecond portion 342 b that lie at respective ends of the first and second sidewall parts 34A1 and 34A2 and are connected to each other into a V-shape, athird portion 342 c that lies at an end of theextended portion 34B, afourth portion 342 d that lies at an end of theextended portion 34C, and a near-fieldlight generating edge 342 e that lies at an end of the plasmon exciting part 341 (propagative edge 341 a). The near-fieldlight generating edge 342 e generates near-field light based on the surface plasmons excited on the plasmonexciting part 341. The near-fieldlight generating edge 342 e may have the shape of a perfectly pointed edge whereas it may have an arc shape in a microscopic view. - The
magnetic pole 35 has afirst portion 35A and asecond portion 35B. Thefirst portion 35A is accommodated in the space formed by the V-shapedportion 34A (the first and second sidewall parts 34A1 and 34A2) of theplasmon generator 34. Thesecond portion 35B is located farther from the evanescentlight generating surface 32 c of the core 32 than is thefirst portion 35A. InFIG. 1 toFIG. 4 , the border between thefirst portion 35A and thesecond portion 35B is shown by a chain double-dashed line. - The
first portion 35A is triangular-prism-shaped. Thefirst portion 35A is interposed between the first and second sidewall parts 34A1 and 34A2 of the V-shapedportion 34A of theplasmon generator 34, and is in contact with the first and second sidewall parts 34A1 and 34A2. Thefirst portion 35A has a constant width in a direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) regardless of the distance from themedium facing surface 12 a. - As shown in
FIG. 1 , thesecond portion 35B has a front part 35B1 and a rear part 35B2. The front part 35B1 has an end face located in themedium facing surface 12 a. The rear part 35B2 is connected to an end of the front part 35B1 opposite from themedium facing surface 12 a. The front part 35B1 has a constant width in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) regardless of the distance from themedium facing surface 12 a, the width being greater than that of thefirst portion 35A. The width of the rear part 35B2 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) is equal to that of the front part 35B1 at the border with the front part 35B1, and increases with increasing distance from themedium facing surface 12 a. - As shown in
FIG. 1 andFIG. 2 , themagnetic pole 35 has anend face 351 located in themedium facing surface 12 a. Theend face 351 includes afirst portion 351 a and asecond portion 351 b. Thefirst portion 351 a is the end face of thefirst portion 35A. Thesecond portion 351 b is the end face of thesecond portion 35B. Thesecond portion 351 b is also the end face of the front part 35B1. Thefirst portion 351 a has a triangular shape and is interposed between the first andsecond portions front end face 342 of theplasmon generator 34. Thefirst portion 351 a has atip 351 c located at its bottom end. - As shown in
FIG. 1 , the width of the core 32 in the track width direction TW (Y direction) in the vicinity of theplasmon generator 34 will be represented by the symbol WWG. The thickness (dimension in the Z direction) of the core 32 in the vicinity of theplasmon generator 34 will be represented by the symbol TWG. WWG falls within the range of 0.3 to 100 μm for example. TWG falls within the range of 0.1 to 4 μm, for example. As shown inFIG. 9 , thecore 32 excluding the part in the vicinity of theplasmon generator 34 may have a width greater than WWG. In the example shown inFIG. 9 , thecore 32 excluding the part in the vicinity of theplasmon generator 34 has a width of 4 μm. - As shown in
FIG. 1 , the dimension of the first andsecond portions front end face 342 of theplasmon generator 34 in the track width direction TW (Y direction) will be represented by the symbol WPGA. The dimension of the first andsecond portions core 32. The dimension of the first and second sidewall parts 34A1 and 34A2 in a direction perpendicular to the evanescentlight generating surface 32 c (Z direction) is equal to TPG. TPG preferably falls within the range of 200 to 400 nm. The reason will be detailed later. - WPGA is determined by TPG and the angle θ formed between the two surfaces of the V-shaped
portion 34A on opposite sides in the track width direction TW (seeFIG. 2 ). More specifically, WPGA=2×TPG×tan(θ/2). The angle θ preferably falls within the range of 30 to 120 degrees. - As shown in
FIG. 1 , the widths of thethird portion 342 c and thefourth portion 342 d of thefront end face 342 of theplasmon generator 34 in the track width direction TW (Y direction) will be represented by the symbols WPGB and WPGC, respectively. In the present embodiment, WPGB and WPGC are equal. WPGB and WPGC fall within the range of 0.5 to 20 μm, for example. InFIG. 1 , theextended portions medium facing surface 12 a. However, theextended portions medium facing surface 12 a. - As shown in
FIG. 3 , the length of theplasmon generator 34 in the X direction will be represented by the symbol HPG. HPG falls within the range of 0.6 to 4.0 μm, for example. The X-direction length of a portion of the plasmonexciting part 341 of theplasmon generator 34, the portion being opposed to the evanescentlight generating surface 32 c, will be represented by the symbol HBF. The distance between the plasmonexciting part 341 and the evanescentlight generating surface 32 c will be represented by the symbol TBF. Both HBF and TBF are important parameters in achieving appropriate excitation and propagation of surface plasmons. HBF preferably falls within the range of 0.6 to 4.0 μm, and is preferably greater than the wavelength of the laser light to be propagated through thecore 32. In the example shown inFIG. 3 , theend face 32 b of thecore 32 is located in themedium facing surface 12 a, so that HBF is equal to HPG. TBF preferably falls within the range of 10 to 100 nm. As shown inFIG. 2 , the distance between the near-fieldlight generating edge 342 e of thefront end face 342 of theplasmon generator 34 and theend face 32 b of thecore 32 is equal to TBF. - As shown in
FIG. 2 , the distance between the near-fieldlight generating edge 342 e of thefront end face 342 of theplasmon generator 34 and thetip 351 c of thefirst portion 351 a of theend face 351 of themagnetic pole 35 will be represented by the symbol D1. The dimension of thefront end face 342 on a virtual straight line L is equal to D1, the virtual straight line L passing through the near-fieldlight generating edge 342 e and extending in the direction perpendicular to the evanescentlight generating surface 32 c. D1 preferably falls within the range of 20 to 70 nm. The reason will be detailed later. - As shown in
FIG. 3 , the distance between the medium facingsurface 12 a and the end face of thecoupling layer 36 closer to themedium facing surface 12 a will be represented by the symbol HPD. HPD falls within the range of 0.3 to 1.0 μm, for example. - Reference is now made to
FIG. 3 to describe the principle of generation of near-field light in the present embodiment and the principle of thermally-assisted magnetic recording using the near-field light.Laser light 46 emitted from thelaser diode 60 is propagated through thecore 32 of the waveguide to reach the vicinity of theplasmon generator 34. Here, thelaser light 46 is totally reflected at the evanescentlight generating surface 32 c which is the interface between the core 32 and thebuffer part 33A. This generatesevanescent light 47 permeating into thebuffer part 33A. Then, theevanescent light 47 and fluctuations of charges on the plasmon exciting part 341 (propagative edge 341 a) of the outer surface of theplasmon generator 34 are coupled with each other to induce a surface plasmon polariton mode. In this way, surface plasmons are excited on the plasmon exciting part 341 (propagative edge 341 a) through coupling with theevanescent light 47 generated from the evanescentlight generating surface 32 c. - The surface plasmons excited on the plasmon exciting part 341 (
propagative edge 341 a) of the outer surface of theplasmon generator 34 are transformed into edge plasmons to propagate along thepropagative edge 341 a to the near-fieldlight generating edge 342 e. Consequently, the edge plasmons concentrate at the near-fieldlight generating edge 342 e, and near-field light 48 occurs from the near-fieldlight generating edge 342 e based on the edge plasmons. The near-field light 48 is projected toward themagnetic disk 201, reaches the surface of themagnetic disk 201, and heats a part of the magnetic recording layer of themagnetic disk 201. This lowers the coercivity of the part of the magnetic recording layer. In thermally-assisted magnetic recording, the part of the magnetic recording layer with the lowered coercivity is subjected to a write magnetic field produced by themagnetic pole 35 for data writing. - Reference is now made to
FIG. 10 to describe the circuit configuration of thecontrol circuit 230 shown inFIG. 5 and the operation of the thermally-assistedmagnetic recording head 1. Thecontrol circuit 230 includes a control LSI (large scale integrated circuit) 100, a ROM (read only memory) 101 connected to thecontrol LSI 100, awrite gate 111 connected to thecontrol LSI 100, and awrite circuit 112 connected to thewrite gate 111 and thecoil 40. - The
control circuit 230 further includes a constantcurrent circuit 121 connected to theMR element 22 and thecontrol LSI 100, anamplifier 122 connected to theMR element 22, and ademodulator circuit 123 connected to an output of theamplifier 122 and thecontrol LSI 100. - The
control circuit 230 further includes alaser control circuit 131 connected to thelaser diode 60 and thecontrol LSI 100, and atemperature detector 132 connected to thecontrol LSI 100. - The
control LSI 100 supplies write data and a write control signal to thewrite gate 111. Thecontrol LSI 100 supplies a read control signal to the constantcurrent circuit 121 and thedemodulator circuit 123, and receives read data output from thedemodulator circuit 123. Thecontrol LSI 100 supplies a laser ON/OFF signal and an operating current control signal to thelaser control circuit 131. Thetemperature detector 132 detects the temperature of the magnetic recording layer of themagnetic disk 201, and supplies this temperature information to thecontrol LSI 100. TheROM 101 contains a control table and the like for controlling the value of the operating current to be supplied to thelaser diode 60. - In a write operation, the
control LSI 100 supplies write data to thewrite gate 111. Thewrite gate 111 supplies the write data to thewrite circuit 112 only when the write control signal indicates a write operation. According to the write data, thewrite circuit 112 passes a write current through thecoil 40. Consequently, themagnetic pole 35 produces a write magnetic field and data is written on the magnetic recording layer of themagnetic disk 201 through the use of the write magnetic field. - In a read operation, the constant
current circuit 121 supplies a certain sense current to theMR element 22 only when the read control signal indicates a read operation. The output voltage of theMR element 22 is amplified by theamplifier 122 and input to thedemodulator circuit 123. When the read control signal indicates a read operation, thedemodulator circuit 123 demodulates the output of theamplifier 122 to generate read data, and supplies the read data to thecontrol LSI 100. - The
laser control circuit 131 controls the supply of the operating current to thelaser diode 60 on the basis of the laser ON/OFF signal, and also controls the value of the operating current to be supplied to thelaser diode 60 on the basis of the operating current control signal. When the laser ON/OFF signal indicates an ON operation, thelaser control circuit 131 exercises control so that an operating current at or above an oscillation threshold is supplied to thelaser diode 60. Consequently, thelaser diode 60 emits laser light, and the laser light is propagated through thecore 32. According to the principle of generation of near-field light described previously, the near-field light 48 occurs from the near-fieldlight generating edge 342 e of theplasmon generator 34. The near-field light 48 heats a part of the magnetic recording layer of themagnetic disk 201, thereby lowering the coercivity of that part. When writing, the part of the magnetic recording layer with the lowered coercivity is subjected to the write magnetic field produced by themagnetic pole 35 for performing data writing. - On the basis of such factors as the temperature of the magnetic recording layer of the
magnetic disk 201 measured by thetemperature detector 132, thecontrol LSI 100 consults the control table stored in theROM 101 to determine the value of the operating current of thelaser diode 60. Using the operating current control signal, thecontrol LSI 100 controls thelaser control circuit 131 so that the operating current of that value is supplied to thelaser diode 60. The control table contains, for example, data that indicates the oscillation threshold and the temperature dependence of the light output versus operating current characteristic of thelaser diode 60. The control table may further contain data that indicates the relationship between the operating current value and a temperature increase of the magnetic recording layer heated by the near-field light 48, and data that indicates the temperature dependence of the coercivity of the magnetic recording layer. - As shown in
FIG. 10 , thecontrol circuit 230 has the signal system for controlling thelaser diode 60, i.e., the signal system consisting of the laser ON/OFF signal and the operating current control signal, independent of the control signal system intended for read/write operations. This configuration makes it possible to implement various modes of energization of thelaser diode 60, not only to energize thelaser diode 60 simply in association with a write operation. It should be noted that the circuit configuration of thecontrol circuit 230 is not limited to the one shown inFIG. 10 . - Now, a method of manufacturing the
slider 10 of the present embodiment will be described briefly. The method of manufacturing theslider 10 includes the steps of forming components of a plurality ofsliders 10 other than theslider substrates 11 on a substrate that includes portions to become theslider substrates 11 of the plurality ofsliders 10, thereby fabricating a substructure that includes a plurality of rows of pre-slider portions, the pre-slider portions being intended to become thesliders 10 later; and forming the plurality ofsliders 10 by cutting the substructure to separate the plurality of pre-slider portions from each other. In the step of forming the plurality ofsliders 10, the surfaces formed by the cutting are polished into the medium facing surfaces 11 a and 12 a. - Reference is now made to
FIG. 11 toFIG. 15 to describe an example of the method of forming theplasmon generator 34 and themagnetic pole 35.FIG. 11 toFIG. 15 each show a part of a stack of layers fabricated in the process of forming theplasmon generator 34 and themagnetic pole 35.FIG. 11 toFIG. 15 each show a cross section in the position where themedium facing surface 12 a is to be formed. -
FIG. 11 shows a step of the method of forming theplasmon generator 34 and themagnetic pole 35. In this step, thecore 32 of the waveguide is initially formed on the cladlayer 31 and then adielectric layer 331 is formed to cover the cladlayer 31 and thecore 32. Thedielectric layer 331 is made of the same material as that of the cladlayer 33. -
FIG. 12 shows the next step. In this step, an etching mask is initially formed on thedielectric layer 331. The etching mask has an opening that has a shape corresponding to the planar shape of the V-shapedportion 34A of theplasmon generator 34 to be formed later. Using the etching mask, thedielectric layer 331 is then etched by reactive ion etching or ion milling, for example. A V-shapedgroove 331 a is thereby formed in thedielectric layer 331. Thegroove 331 a is formed so that its bottom end reaches the evanescentlight generating surface 32 c of thecore 32. The etching mask is then removed. -
FIG. 13 shows the next step. In this step, adielectric film 332 is formed by, for example, sputtering, so as to cover the entire top surface of the stack shown inFIG. 12 . Thedielectric film 332 is made of the same material as that of the cladlayer 33. Thedielectric film 332 is formed also in thegroove 331 a. Thedielectric layer 331 and thedielectric film 332 constitute the cladlayer 33. Thegroove 33 b of the cladlayer 33 has a depth (dimension in the Z direction) of 200 nm, for example. -
FIG. 14 shows the next step. In this step, ametal film 34P is formed by, for example, sputtering, so as to cover the entire top surface of the stack shown inFIG. 13 . Themetal film 34P is to become theplasmon generator 34 later. -
FIG. 15 shows the next step. In this step, themetal film 34P is initially patterned by etching a part of themetal film 34P by ion milling, for example. As a result, the remainingmetal film 34P becomes theplasmon generator 34. Next, themagnetic pole 35 is formed on theplasmon generator 34 by frame plating, for example. The thickness of the magnetic pole 35 (the distance between the bottom end of thegroove 33 b and the top surface of the magnetic pole 35) is greater than the depth of thegroove 33 b. For example, if the depth of thegroove 33 b is 200 nm, the thickness of themagnetic pole 35 is 450 nm. - When the foregoing substructure is completed, the substructure is cut near the positions where the medium facing surfaces 12 a are to be formed, so that the plurality of pre-slider portions are separated from each other. Subsequently, the surfaces formed by the cutting are polished into the medium facing surfaces 12 a.
- The effects of the thermally-assisted
magnetic recording head 1 according to the present embodiment will now be described. The outer surface of theplasmon generator 34 of the present embodiment includes the plasmonexciting part 341 and thefront end face 342. The plasmonexciting part 341 faces the evanescentlight generating surface 32 c of the core 32 with a predetermined distance therebetween. Thefront end face 342 is located in themedium facing surface 12 a. Thefront end face 342 has the near-fieldlight generating edge 342 e lying at an end of the plasmonexciting part 341. Surface plasmons are excited on the plasmonexciting part 341 through coupling with the evanescent light that occurs from the evanescentlight generating surface 32 c. The near-fieldlight generating edge 342 e generates near-field light based on the surface plasmons excited on the plasmonexciting part 341. - According to the present embodiment, it is possible to transform the laser light that is propagated through the core 32 into near-field light with higher efficiency, as compared with the conventional technique of directly irradiating a plasmon antenna with laser light to produce near-field light from the plasmon antenna.
- In the present embodiment, the
plasmon generator 34 has the V-shapedportion 34A and theextended portions portion 34A has the first and second sidewall parts 34A1 and 34A2. Thefront end face 342 of theplasmon generator 34 includes the first andsecond portions extended portion 34B, and thefourth portion 342 d lying at the end of theextended portion 34C. Theextended portions plasmon generator 34 to outside. More specifically, according to the present embodiment, the outer surface of theplasmon generator 34 in contact with air and other components of the thermally-assisted magnetic head can be increased in area as much as theextended portions plasmon generator 34 does not have the extendedportions plasmon generator 34 can be more effectively dissipated to outside. The present embodiment thus makes it possible to suppress a rise in temperature of theplasmon generator 34. This effect will be detailed below. - The outer surface of the
plasmon generator 34 includes thefront end face 342, which is exposed in themedium facing surface 12 a and is in contact with air. When the thermally-assisted magnetic recording head is in use, the heat of theplasmon generator 34 is dissipated at themedium facing surface 12 a by the airflow that passes between the medium facingsurface 12 a and themagnetic disk 201. According to the present embodiment, thefront end face 342 of theplasmon generator 34 in contact with air is increased in area as much as theextended portions fourth portions plasmon generator 34 does not have the extendedportions plasmon generator 34 by means of the airflow mentioned above, and consequently makes it possible to suppress a rise in temperature of theplasmon generator 34. - Portions of the outer surface of the
plasmon generator 34 other than thefront end face 342 are in contact with other components of the thermally-assisted magnetic head. In such portions, the heat generated in theplasmon generator 34 is dissipated from theplasmon generator 34 by conduction to other components. According to the present embodiment, the portions of the outer surface of theplasmon generator 34 other than thefront end face 342 are increased in area as compared with the case where theplasmon generator 34 does not have the extendedportions plasmon generator 34 by the conduction of the heat generated in theplasmon generator 34 to other components, and consequently makes it possible to suppress a rise in temperature of theplasmon generator 34. - In the present embodiment, in particular, the
magnetic pole 35 is in contact with theplasmon generator 34. Themagnetic pole 35 is also in contact with thetop yoke layer 43 of high volume via thecoupling layer 36. Themagnetic pole 35 is made of a magnetic metal material which is higher in thermal conductivity than insulating materials such as alumina. Consequently, according to the present embodiment, the heat generated in theplasmon generator 34 can be effectively dissipated through themagnetic pole 35, thecoupling layer 36, and thetop yoke layer 43 with a significant effect of suppressing a rise in temperature of theplasmon generator 34. In the present embodiment, as viewed from above, the outer edges of theextended portions plasmon generator 34 lie outside the outer edges of themagnetic pole 35. This makes it possible to make theextended portions magnetic pole 35, so that it is possible to promote the heat dissipation from theplasmon generator 34. - From the foregoing, according to the present embodiment, it is possible to prevent the
front end face 342 of theplasmon generator 34 from protruding from themedium facing surface 12 a due to an excessive rise in temperature of theplasmon generator 34, and to prevent a reduction in use efficiency of the light in theplasmon generator 34. - Now, a description will be given of the results of a first simulation demonstrating that the present embodiment makes it possible to suppress a rise in temperature of the
plasmon generator 34. In the first simulation, two models of thermally-assisted magnetic recording heads to be described later, namely, a model of a comparative example and a model of a practical example, were measured for the following temperatures: the temperature at the near-fieldlight generating edge 342 e of thefront end face 342 of the plasmon generator 34 (hereinafter, referred to as the temperature of the plasmon generator 34); and the temperature of the evanescentlight generating surface 32 c of the core 32 at the portion opposed to the near-fieldlight generating edge 342 e (hereinafter, referred to as the temperature of the core 32). - The
plasmon generator 34 of the model of the comparative example is without theextended portions plasmon generator 34 of the model of the practical example has the extendedportions FIG. 1 are 5 μm. - For the first simulation, Au was selected as the material of the
plasmon generator 34. TPG shown inFIG. 1 was set to 200 nm, θ shown inFIG. 2 was set to 90 degrees, and HPG shown inFIG. 3 was set to 1.2 μm. TBF shown inFIG. 2 andFIG. 3 was set to 35 nm, D1 shown inFIG. 2 was set to 30 nm, and HPD shown inFIG. 3 was set to 0.5 μm. Energy for theplasmon generator 34 to be transformed into heat per second was set to 8.3 mW. - Table 1 shows the results of the first simulation. From Table 1, it can be seen that both the temperature of the
plasmon generator 34 and that of the core 32 are lower in the model of the practical example than in the model of the comparative example. The reason is considered to be that in the model of the practical example, theextended portions plasmon generator 34 as compared with the model of the comparative example. -
TABLE 1 Temperature of Temperature of the the core 32 (° C.) plasmon generator 34 (° C.) Model of comparative 132 234 example Model of practical 103 179 example - As can be seen from the results of the first simulation, according to the present embodiment, the heat dissipation from the
plasmon generator 34 is promoted by theextended portions plasmon generator 34 does not have the extendedportions plasmon generator 34. - The other effects of the present embodiment will now be described. In the present embodiment, the
plasmon generator 34 made of a metal is in contact with themagnetic pole 35 made of a magnetic metal material. Theplasmon generator 34 is thus not electrically isolated. According to the present embodiment, it is therefore possible to avoid the occurrence of electrical static discharge (ESD) in theplasmon generator 34. - In the present embodiment, the
magnetic pole 35 is disposed such that theplasmon generator 34 is interposed between themagnetic pole 35 and thecore 32. With such a configuration, according to the present embodiment, theend face 351 of themagnetic pole 35 for generating the write magnetic field and the near-fieldlight generating edge 342 e of theplasmon generator 34 for generating the near-field light can be put close to each other in themedium facing surface 12 a. This makes it possible to implement an advantageous configuration for thermally-assisted magnetic recording. Moreover, according to the present embodiment, since theplasmon generator 34 made of a nonmagnetic metal is interposed between the core 32 and themagnetic pole 35, it is possible to prevent the laser light propagated through the core 32 from being absorbed by themagnetic pole 35. This can improve the use efficiency of the laser light propagated through thecore 32. - In the present embodiment, the first and second sidewall parts 34A1 and 34A2 are each connected to the plasmon
exciting part 341, and increase in distance from each other with increasing distance from the plasmonexciting part 341. Themagnetic pole 35 has thefirst portion 35A interposed between the first and second sidewall parts 34A1 and 34A2. Thefront end face 342 of theplasmon generator 34 has the first andsecond portions end face 351 of themagnetic pole 35 located in themedium facing surface 12 a has a triangular portion interposed between the first andsecond portions front end face 342, that is, thefirst portion 351 a. Thefirst portion 351 a has thetip 351 c located at its bottom end. In thefirst portion 351 a, thetip 351 c is closest to thebottom shield layer 29. Magnetic fluxes therefore concentrate at the vicinity of thetip 351 c of thefirst portion 351 a, so that a high write magnetic field occurs from the vicinity of thetip 351 c. Consequently, according to the present embodiment, the position where a high write magnetic field occurs in thefirst portion 351 a can be brought closer to the near-fieldlight generating edge 342 e of theplasmon generator 34 which generates near-field light. According to the present embodiment, it is thus possible to put the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other while preventing the laser light propagated through the core 32 from being absorbed by themagnetic pole 35. - Now, a description will be given of the results of a second simulation demonstrating that the present embodiment makes it possible to locate the position of occurrence of the write magnetic field and the position of occurrence of the near-field light close to each other. Initially, two types of models of thermally-assisted magnetic recording heads used in the second simulation, namely, a model of a first type and a model of a second type, will be described with reference to
FIG. 16 andFIG. 17 . -
FIG. 16 is a front view showing a core, a plasmon generator, and a magnetic pole in the medium facing surface of the model of the first type. As shown inFIG. 16 , the model of the first type includes aplasmon generator 1034 and amagnetic pole 1035, instead of theplasmon generator 34 and themagnetic pole 35 of the embodiment. Theplasmon generator 1034 is triangular-prism-shaped. The outer surface of theplasmon generator 1034 includes a propagative edge and afront end face 1342. The propagative edge faces the evanescentlight generating surface 32 c of the core 32 with a predetermined distance therebetween. Thefront end face 1342 has a triangular shape. Thefront end face 1342 has a near-fieldlight generating edge 1342 e lying at an end of the above-mentioned propagative edge. - The
magnetic pole 1035 does not include any portion corresponding to thefirst portion 35A of themagnetic pole 35 of the embodiment. Themagnetic pole 1035 is located on a side of theplasmon generator 1034 opposite from thecore 32, at a predetermined distance from theplasmon generator 1034. Themagnetic pole 1035 has anend face 1351 located in themedium facing surface 12 a. Theend face 1351 has a rectangular shape. Theend face 1351 has abottom end 1351 a that is closer to the evanescentlight generating surface 32 c of thecore 32. -
FIG. 17 is a front view showing a core, a plasmon generator, and a magnetic pole in the medium facing surface of the model of the second type. As shown inFIG. 17 , the model of the second type includes aplasmon generator 2034 and amagnetic pole 2035, instead of theplasmon generator 34 and themagnetic pole 35 of the embodiment. Theplasmon generator 2034 has the same configuration as that of theplasmon generator 34 of the embodiment except that there is noextended portion magnetic pole 2035 has the same configuration as that of themagnetic pole 35 of the embodiment. Hereinafter, substantially the same components as in the embodiment will be designated by like reference numerals for description. The outer surface of theplasmon generator 2034 includes a plasmonexciting part 341 and afront end face 342. Theplasmon generator 2034 has a V-shapedportion 34A. The V-shapedportion 34A has first and second sidewall parts 34A1 and 34A2. Thefront end face 342 has first andsecond portions light generating edge 342 e. In the model of the second type, thefront end face 342 does not have the third andfourth portions - The
magnetic pole 2035 has first andsecond portions magnetic pole 2035 also has anend face 351. Theend face 351 has afirst portion 351 a and asecond portion 351 b. Thefirst portion 351 a has atip 351 c. InFIG. 17 , the border between thefirst portion 35A (thefirst portion 351 a) and thesecond portion 35B (thesecond portion 351 b) is shown by a chain double-dashed line. - The model of the second type is a model for showing the relationship between the position of occurrence of the write magnetic field and the position of occurrence of the near-field light according to the embodiment. The
plasmon generator 2034 of the second type does not include theextended portions extended portions - The conditions of the second simulation will now be described. For the second simulation, FeCo was selected as the material of the
magnetic poles plasmon generators magnetic poles top yoke layer 43 in the X direction was set to 12 μm. The dimension of thetop yoke layer 43 in the track width direction TW (Y direction) was set to 17 μm (seeFIG. 9 ). - For the model of the first type, as shown in
FIG. 16 , the distance between the near-fieldlight generating edge 1342 e of thefront end face 1342 of theplasmon generator 1034 and theend face 32 b of the core 32 will be represented by the symbol TBF1. The distance between the near-fieldlight generating edge 1342 e and thebottom end 1351 a of theend face 1351 of themagnetic pole 1035 will be represented by the symbol D21. For the second simulation, TBF1 was set to 50 nm, and D21 was set to 120 nm. - For the model of the second type, as shown in
FIG. 17 , the distance between the near-fieldlight generating edge 342 e of thefront end face 342 of theplasmon generator 1034 and theend face 32 b of the core 32 will be represented by the symbol TBF2. The distance between the near-fieldlight generating edge 342 e and thetip 351 c will be represented by the symbol D12. The distance between the near-fieldlight generating edge 342 e and thesecond portion 351 b will be represented by the symbol D22. D22 is equal to the dimension TPG of the first and second sidewall parts 34A1 and 34A2 in the Z direction (seeFIG. 1 ). For the second simulation, TBF2 was set to 50 nm, D12 was set to 50 nm, and D22 was set to 120 nm. The angle θ formed between the two surfaces of the V-shapedportion 34A on opposite sides in the track width direction (Y direction) was set to 75 degrees. - In the second simulation, an effective write magnetic field Heff was determined for both the model of the first type and the model of the second type. The effective write magnetic field refers to a write magnetic field that the magnetic pole effectively exerts on the magnetic recording layer of the
magnetic disk 201 so that the magnetization of the magnetic recording layer is inverted to form a recording bit. The effective write magnetic field Heff is expressed by the following equation: -
H eff={(H P 2 +H T 2)1/3 +H L 2/3/}3/2, - where HP is the component of the write magnetic field in a direction perpendicular to the magnetic recording layer (X direction), HT is the component in the track width direction (Y direction), and HL is the component in a track-extending direction (Z direction).
- The results of the second simulation will now be described with reference to
FIG. 18 .FIG. 18 is a characteristic chart showing the effective write magnetic field Heff determined by the second simulation. InFIG. 18 , the horizontal axis shows the position on themedium facing surface 12 a in the track-extending direction (Z direction). The vertical axis shows the effective write magnetic field Heff. The unit of Heff is Oe (1 Oe=79.6 A/m). InFIG. 18 , the broken line shows the effective write magnetic field Heff of the model of the first type, and the solid line shows the effective write magnetic field Heff of the model of the second type. - On the horizontal axis of
FIG. 18 , 0 μm indicates the position of thebottom end 1351 a of theend face 1351 of themagnetic pole 1035 of the model of the first type and the position of the border between thefirst portion 351 a and thesecond portion 351 b of theend face 351 of themagnetic pole 2035 of the model of the second type. Positions that are on the trailing end side (Z direction) relative to the 0-μm position are expressed in positive values. Positions that are on the leading end side (−Z direction) relative to the 0-μm position are expressed in negative values. The near-fieldlight generating edge 1342 e of thefront end face 1342 of theplasmon generator 1034 of the model of the first type and the near-fieldlight generating edge 342 e of thefront end face 342 of theplasmon generator 2034 of the model of the second type are located at a position of −0.12 μm. - It can be seen from
FIG. 18 that in the model of the second type, as compared with the model of the first type, the position of the maximum peak of the effective write magnetic field Heff shifts to the leading end side (−Z direction), coming closer to the position of the near-fieldlight generating edge 342 e, i.e., the position of −120 μm. The effective write magnetic field Heff at the position of −120 nm was 4119 Oe in the model of the first type, and 8986 Oe in the model of the second type. Consequently, in the model of the second type, the effective write magnetic field Heff at the position of the near-fieldlight generating edge 342 e was approximately twice the effective write magnetic field Heff at the position of the near-fieldlight generating edge 1342 e in the model of the first type. - As can be seen from the results of the second simulation, according to the present embodiment, it is possible to put the position of occurrence of the write magnetic field close to the position of occurrence of the near-field light, and consequently, it is possible to increase the write magnetic field at the position of occurrence of the near-field light.
- Next, a description will be given of the results of a third simulation that was performed to examine the preferred range of the dimension D1 of the
front end face 342 on the virtual straight line L shown inFIG. 2 . The third simulation used the model of the second type shown inFIG. 17 . D12 shown inFIG. 17 corresponds to D1 shown inFIG. 2 . In the third simulation, D12 was varied within the range from 20 nm to 70 nm. - The conditions of the third simulation other than D12 will now be described. For the third simulation, tantalum oxide was selected as the material of the core 32, alumina was selected as the material of the
clad layers plasmon generator 34. The width WWG of the core 32 in the vicinity of theplasmon generator 2034 was set to 0.5 μm. The thickness TWG of the core 32 was set to 0.4 μm (seeFIG. 1 ). The width of thesecond portion 35B of themagnetic pole 2035 in themedium facing surface 12 a was set to 0.24 μm. The length of theplasmon generator 2034 and that of themagnetic pole 2035 in the X direction were both set to 1.5 μm. D22 shown inFIG. 17 (TPG shown inFIG. 1 ) was set to 175 nm. The radius of curvature of the near-fieldlight generating edge 342 e was set to 15 nm. - In the third simulation, the laser light to be incident on and propagated through the
core 32 was a Gaussian beam polarized in TM mode (where the electric field of the laser light oscillates in the direction perpendicular to the evanescentlight generating surface 32 c of the core 32) with a wavelength of 823 nm and an incident intensity of 1.0 V2/m2. Using the three-dimensional finite-difference time-domain method (FDTD method), the peak intensity of the laser light at theend face 32 b of the core 32 (hereinafter, referred to as laser light intensity) and the peak intensity of the near-field light at the near-fieldlight generating edge 342 e of thefront end face 342 of the plasmon generator 2034 (hereinafter, referred to as near-field light intensity) were determined. An intensity ratio was defined and determined as the value of the near-field light intensity divided by the laser light intensity. The material of the core 32, being tantalum oxide, has a refractive index of 2.15 at the wavelength of 823 nm. The material of theclad layers -
FIG. 19 and Table 2 show the results of the third simulation. InFIG. 19 , the horizontal axis indicates D12, and the vertical axis indicates the near-field light intensity. -
TABLE 2 Near-field light Laser light Intensity D12 (nm) intensity (V2/m2) intensity (V2/m2) ratio 20 0.432 0.085 5.082 30 0.673 0.079 8.519 40 0.876 0.076 11.53 50 1.017 0.082 12.40 70 1.153 0.082 14.06 - It can be seen from
FIG. 19 and Table 1 that the near-field light intensity and the intensity ratio increase with increasing D12. The intensity ratio needs to be 5 or higher in order to form only a desired recording bit on the magnetic recording layer of themagnetic disk 201. It is therefore preferred that D12 be 20 nm or greater. Too large D12, however, hinders the effect of the embodiment that the position of occurrence of the write magnetic field and the position of occurrence of the near-field light can be located close to each other. It has been experimentally known that D12 of 70 nm or less makes it possible to apply a write magnetic field having a desired gradient to the portion of the magnetic recording layer of themagnetic disk 201 that is sufficiently heated by the near-field light. Consequently, it is preferred that D12, or D1 shown inFIG. 2 , fall within the range of 20 to 70 nm. In such a range, D1 is preferably 30 nm or greater, and yet preferably 40 nm or greater, in order to ensure an intensity ratio of 5 or higher. - Next, a description will be given of the results of a fourth simulation that was performed to examine the preferred range of the dimension TPG shown in
FIG. 1 . The fourth simulation used the model of the practical example which was used in the first simulation. TPG shown inFIG. 1 was varied to be 170 nm, 200 nm, and 230 nm. - In the fourth simulation, the light density distribution of the near-field light at the surface of a magnetic recording medium located 8 nm away from the
medium facing surface 12 a was determined by using a three-dimensional finite-difference time-domain method similar to that used in the third simulation. From the light density distribution, the spot diameter of the near-field light (hereinafter, referred to as light spot diameter) and the maximum light density were determined. The light spot diameter was defined as the full width at half maximum in the light density distribution. The rest of the conditions of the fourth simulation were the same as those of the model of the practical example in the first simulation. - Table 3 shows the results of the fourth simulation. It can be seen from Table 3 that TPG of 200 nm or greater can make the maximum light density higher than when TPG is 170 nm, and make both the maximum light density and the light spot diameter constant. It is therefore preferred that TPG be 200 nm or greater. Too large TPG, on the other hand, makes the V-shaped
groove 331 a shown inFIG. 12 too deep, thereby making it difficult to form thegroove 331 a. In such a point of view, it is preferred that TPG be 400 nm or less. Consequently, it is preferred that TPG fall within the range of 200 to 400 nm. -
TABLE 3 Maximum light Light spot TPG (nm) density (V2/m2) diameter (nm) 170 0.71 54.4 200 0.8 57 230 0.8 57 - A second embodiment of the invention will now be described with reference to
FIG. 20 andFIG. 21 .FIG. 20 is a perspective view showing the core of the waveguide, the plasmon generator, and the magnetic pole of the thermally-assisted magnetic recording head according to the present embodiment.FIG. 21 is a plan view showing the plasmon exciting part of the plasmon generator shown inFIG. 20 as viewed from above. Theplasmon generator 34 of the present embodiment has afirst portion 34D and asecond portion 34E, instead of the V-shapedportion 34A of the first embodiment. Thefirst portion 34D has an end face located in themedium facing surface 12 a. Thesecond portion 34E is located farther from themedium facing surface 12 a than is thefirst portion 34D, such that thesecond portion 34E is continuous with thefirst portion 34D. InFIG. 20 , the border between thefirst portion 34D and thesecond portion 34E is shown by a chain double-dashed line. - The
first portion 34D has a bottom part 34D1 that is shaped like a plate and faces the evanescentlight generating surface 32 c, and first and second sidewall parts 34D2 and 34D3 that are each shaped like a plate. The sidewall parts 34D2 and 34D3 are located farther from the evanescentlight generating surface 32 c than is the bottom part 34D1. The bottom part 34D1 connects the first and second sidewall parts 34D2 and 34D3 to each other at their respective edges closer to the evanescentlight generating surface 32 c. - The bottom part 34D1 has a width that decreases with decreasing distance to the
medium facing surface 12 a, the width being in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction). The bottom part 34D1 has an end located in themedium facing surface 12 a. At this end of the bottom part 34D1, the bottom part 34D1 has a zero width and the respective bottom ends of the first and second sidewall parts 34D2 and 34D3 are in contact with each other. - The distance between the first and second sidewall parts 34D2 and 34D3 in the direction parallel to the
medium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) increases with increasing distance from the evanescentlight generating surface 32 c, and decreases with decreasing distance to themedium facing surface 12 a. - The
second portion 34E has a bottom part 34E1 that is continuous with the bottom part 34D1 of thefirst portion 34D, a first sidewall part 34E2 that is continuous with the first sidewall part 34D2 of thefirst portion 34D, and a second sidewall part 34E3 that is continuous with the second sidewall part 34D3 of thefirst portion 34D. The bottom part 34E1 has a constant width in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) regardless of the distance from themedium facing surface 12 a. - The distance between the first and second sidewall parts 34E2 and 34E3 in the direction parallel to the
medium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) increases with increasing distance from the evanescentlight generating surface 32 c, but does not change according to the distance from themedium facing surface 12 a. - As shown in
FIG. 20 , thefirst portion 34D and thesecond portion 34E of theplasmon generator 34 form inside a space for accommodating a part of themagnetic pole 35. - In the present embodiment, the
extended portions first portion 34D and thesecond portion 34E in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction). As viewed from above, the outer edges of theextended portions magnetic pole 35. In the present embodiment, thesecond portion 35B of themagnetic pole 35 is in contact with theextended portions - The plasmon
exciting part 341 of the present embodiment includes aflat surface part 341 b instead of thepropagative edge 341 a of the first embodiment. Theflat surface part 341 b includes awidth changing portion 341 b 1 and aconstant width portion 341 b 2. Thewidth changing portion 341b 1 is formed by a surface of the bottom part 34D1 of thefirst portion 34D that is closer to the evanescentlight generating surface 32 c. Theconstant width portion 341 b 2 is formed by a surface of the bottom part 34E1 of thesecond portion 34E that is closer to the evanescentlight generating surface 32 c. InFIG. 21 , the border between thewidth changing portion 341 b 1 and theconstant width portion 341 b 2 is shown by a chain double-dashed line. - The
width changing portion 341b 1 has a width that decreases with decreasing distance to themedium facing surface 12 a, the width being in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction). Thewidth changing portion 341b 1 has a front end part that is located in themedium facing surface 12 a, and two sides that are opposite in the direction of the width (Y direction). The two sides of thewidth changing portion 341b 1 form the same angle with respect to the direction perpendicular to themedium facing surface 12 a (X direction). The angle falls within the range of 3 to 50 degrees, and preferably within the range of 10 to 25 degrees. - The
constant width portion 341 b 2 is located farther from themedium facing surface 12 a than is thewidth changing portion 341b 1, such that theconstant width portion 341 b 2 is continuous with thewidth changing portion 341b 1. Theconstant width portion 341 b 2 has a constant width in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) regardless of the distance from themedium facing surface 12 a. - In the present embodiment, the
first portion 342 a and thesecond portion 342 b of thefront end face 342 lie at respective ends of the first and second sidewall parts 34D1 and 34D2 of thefirst portion 34D, and are connected to each other into a V-shape. - In the present embodiment, the
first portion 35A of themagnetic pole 35 is accommodated in the space formed by thefirst portion 34D and thesecond portion 34E of theplasmon generator 34. Thefirst portion 35A includes a front part 35A1 and a rear part 35A2. The front part 35A1 is accommodated in the space formed by thefirst portion 34D (the bottom part 34D1, the first sidewall part 34D2, and the second sidewall part 34D3) of theplasmon generator 34. The rear part 35A2 is accommodated in the space formed by thesecond portion 34E (the bottom part 34E1, the first sidewall part 34E2, and the second sidewall part 34E3) of theplasmon generator 34. - The front part 35A1 is interposed between the first and second sidewall parts 34D2 and 34D3 of the
first portion 34D of theplasmon generator 34, and is contact with the bottom part 34D1, the first sidewall part 34D2, and the second sidewall part 34D3. The width of the front part 35A1 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) increases with increasing distance from the evanescentlight generating surface 32 c, and decreases with decreasing distance to themedium facing surface 12 a. - The front part 35A1 has an end face located in the
medium facing surface 12 a. Thefirst portion 351 a of theend face 351 of themagnetic pole 35 located in themedium facing surface 12 a is formed by the end face of the front part 35A1. - The rear part 35A2 is interposed between the first and second sidewall parts 34E2 and 34E3 of the
second portion 34E of theplasmon generator 34, and is contact with the bottom part 34E1, the first sidewall part 34E2, and the second sidewall part 34E3. The width of the rear part 35A2 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) increases with increasing distance from the evanescentlight generating surface 32 c, but does not change according to the distance from themedium facing surface 12 a. - The
plasmon generator 34 need not necessarily have thesecond portion 34E. If theplasmon generator 34 does not have thesecond portion 34E, thefirst portion 35A of themagnetic pole 35 does not have the rear part 35A2. - The effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. In the present embodiment, as in the first embodiment, the
plasmon generator 34 has the extendedportions plasmon generator 34, and thereby makes it possible to suppress a rise in temperature of theplasmon generator 34. In the present embodiment, thesecond portion 35B of themagnetic pole 35 is in contact with theextended portions plasmon generator 34. As in the first embodiment, the heat generated in theplasmon generator 34 can thus be effectively dissipated through themagnetic pole 35, thecoupling layer 36, and thetop yoke layer 43. In the present embodiment, as viewed from above, the outer edges of theextended portions magnetic pole 35. This makes it possible, as in the first embodiment, to make theextended portions magnetic pole 35, so that it is possible to promote the heat dissipation from theplasmon generator 34. - In the present embodiment, the plasmon
exciting part 341 of theplasmon generator 34 includes theflat surface part 341 b. Theflat surface part 341 b includes thewidth changing portion 341b 1. The width of thewidth changing portion 341 b 1 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) decreases with decreasing distance to themedium facing surface 12 a. The surface plasmons excited on theflat surface part 341 b are gradually transformed into edge plasmons, which are surface plasmons to propagate along the two sides of thewidth changing portion 341 b 1 that are opposite in the direction of the width (Y direction), while propagating over thewidth changing portion 341b 1. The surface plasmons (including edge plasmons) propagating over thewidth changing portion 341 b 1 reach the near-fieldlight generating edge 342 e. - In the
width changing portion 341b 1, the propagating plasmons increase in electric field intensity. This is presumably based on the following first and second principles. Initially, a description will be given of the first principle. The wave number of the surface plasmons propagating over thewidth changing portion 341 b 1 increases as the width of thewidth changing portion 341 b 1 decreases. As the wave number of the surface plasmons increases, the speed of travel of the surface plasmons decreases. This consequently increases the energy density of the surface plasmons and enhances the electric field-intensity of the surface plasmons. - Next, a description will be given of the second principle. When the surface plasmons propagate over the
width changing portion 341b 1, some of the surface plasmons impinge on the two sides of thewidth changing portion 341 b 1 that are opposite in the direction of the width (Y direction) to scatter, thereby generating a plurality of plasmons with different wave numbers. Some of the plurality of plasmons thus generated are transformed into edge plasmons having a wave number higher than that of the surface plasmons propagating over a flat surface. In this way, the surface plasmons are gradually transformed into the edge plasmons to propagate along the two sides, whereby the edge plasmons gradually increase in electric field intensity. As compared with the surface plasmons propagating over a flat surface, the edge plasmons are higher in wave number and lower in speed of travel. Consequently, the transformation of the surface plasmons into the edge plasmons increases the energy density of the plasmons. In thewidth changing portion 341b 1, the foregoing transformation of the surface plasmons into the edge plasmons is accompanied by the generation of new surface plasmons based on the evanescent light occurring from the evanescentlight generating surface 32 c. The new surface plasmons are also transformed into edge plasmons. As a result, the edge plasmons increase in electric field intensity. In this way, it is possible to obtain edge plasmons that are higher in electric field intensity than the surface plasmons originally generated. - In the
width changing portion 341b 1, the surface plasmons propagating over the flat surface and the edge plasmons having a wave number higher than that of the surface plasmons coexist. It can be considered that both the surface plasmons and the edge plasmons increase in electric field intensity in thewidth changing portion 341 b 1 based on the first and second principles described above. In thewidth changing portion 341b 1, the electric field intensity of the plasmons can thus be enhanced as compared with a case where either one of the first principle and the second principle is in operation. - In the present embodiment, the
flat surface part 341 b of the plasmonexciting part 341 of theplasmon generator 34 further includes theconstant width portion 341 b 2. Suppose that theflat surface part 341 b does not include theconstant width portion 341 b 2, and thewidth changing portion 341b 1 extends up to the end of theflat surface part 341 b opposite from themedium facing surface 12 a. In such a case, the maximum width of theflat surface part 341 b is greater as compared with the case where theflat surface part 341 b includes theconstant width portion 341 b 2. Then, the width WWG of the core 32 in the vicinity of theplasmon generator 34 needs to be increased to the maximum width of theflat surface part 341 b. Consequently, at least a part of the core 32 in the vicinity of theplasmon generator 34 is likely to enter a multi mode that is capable of propagating a plurality of modes (propagation modes) of light. In this case, the mode that contributes to the excitation of surface plasmons on theflat surface part 341 b weakens to decrease the use efficiency of the light that is propagated through thecore 32. In contrast, according to the present embodiment, theflat surface part 341 b includes theconstant width portion 341 b 2, and it is therefore possible to make the width WWG of the core 32 in the vicinity of theplasmon generator 34 smaller than that in the case where theflat surface part 341 b does not include theconstant width portion 341 b 2. According to the present embodiment, it is therefore possible to bring at least a part of the core 32 in the vicinity of theplasmon generator 34 into a single mode that is capable of propagating only a single mode of light. Consequently, it is possible to improve the use efficiency of the laser light that is propagated through thecore 32. - Moreover, in the present embodiment, the
first portion 34D of theplasmon generator 34 has the bottom part 34D1 and the first and second sidewall parts 34D2 and 34D3. The width of the bottom part 34D1 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) decreases with decreasing distance to themedium facing surface 12 a. The distance between the first and second sidewall parts 34D2 and 34D3 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) increases with increasing distance from the evanescentlight generating surface 32 c, and decreases with decreasing distance to themedium facing surface 12 a. Themagnetic pole 35 includes the front part 35A1 that is interposed between the first and second sidewall parts 34D2 and 34D3 and in contact with the bottom part 34D1, the first sidewall part 34D2 and the second sidewall part 34D3. The width of the front part 35A1 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) decreases with decreasing distance to themedium facing surface 12 a. Consequently, according to the present embodiment, magnetic fluxes passing through themagnetic pole 35 can be concentrated as they approach themedium facing surface 12 a. This makes it possible to produce a high write magnetic field from thefirst portion 351 a of theend face 351. - The present embodiment may be modified so that the plasmon generator of the invention is configured as in the following modification example. In the configuration of the modification example, the V-shaped
portion 34A of the first embodiment is provided between the medium facingsurface 12 a and thefirst portion 34D. In such a case, the plasmonexciting part 341 includes thepropagative edge 341 a and the flat surface part 3431 b. As described previously, themedium facing surface 12 a is formed by polishing a surface that is formed by cutting the substructure. In such a case, the position of themedium facing surface 12 a may slightly vary. Suppose that theplasmon generator 34 is designed not to have the V-shapedportion 34A or thepropagative edge 341 a so that the ends of thefirst portion 34D and thewidth changing portion 341 b 1 are located in themedium facing surface 12 a. If so, variations in the position of themedium facing surface 12 a change the shape of thefront end face 342 of theplasmon generator 34, or the shape of the near-fieldlight generating edge 342 e in particular. As a result, the near-field light occurring from theplasmon generator 34 can vary in characteristic. In contrast, according to the modification example described above, theplasmon generator 34 has the V-shapedportion 34A and thepropagative edge 341 a. This makes it possible that, even if the position of themedium facing surface 12 a somewhat varies, thefront end face 342 of theplasmon generator 34 remains unchanged in shape. According to the foregoing modification example, it is therefore possible to prevent the characteristics of the near-field light generated by theplasmon generator 34 from being changed due to variations in the position of themedium facing surface 12 a. - Moreover, in the foregoing modification example, the
first portion 35A of themagnetic pole 35 has a triangular-prism-shaped portion that is accommodated in the V-shapedportion 34A. The width of the triangular-prism-shaped portion in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) does not change according to the distance from themedium facing surface 12 a. According to the foregoing modification example, it is therefore possible to keep the shape of thefirst portion 351 a of theend face 351 constant even if the position of themedium facing surface 12 a somewhat varies. Consequently, according to the modification example, it is possible to suppress a change in the write characteristics due to variations in the position of themedium facing surface 12 a. - The remainder of configuration, function and effects of the present embodiment are similar to those of the first embodiment.
- A third embodiment of the invention will now be described with reference to
FIG. 22 andFIG. 23 .FIG. 22 is a front view showing a part of the medium facing surface of the head unit of the thermally-assisted magnetic recording head according to the present embodiment.FIG. 23 is a cross-sectional view showing the core of the waveguide, the plasmon generator, and the magnetic pole of the thermally-assisted magnetic recording head according to the present embodiment. The thermally-assisted magnetic recording head according to the present embodiment has aplasmon generator 84 and amagnetic pole 85, instead of theplasmon generator 34 and themagnetic pole 35 of the first embodiment. Theplasmon generator 84 is made of the same material as that of theplasmon generator 34 of the first embodiment. Themagnetic pole 85 is made of the same material as that of themagnetic pole 35 of the first embodiment. - The
plasmon generator 84 has an outer surface that includes a plasmonexciting part 841 and a front end face 842. The plasmonexciting part 841 faces the evanescentlight generating surface 32 c of the core 32 with a predetermined distance therebetween. The front end face 842 is located in themedium facing surface 12 a. Theplasmon generator 84 further has a V-shaped portion 84A that has an end face located in themedium facing surface 12 a. The V-shaped portion 84A has a first sidewall part 84A1 and a second sidewall part 84A2 that are each connected to the plasmonexciting part 841, and that increase in distance from each other with increasing distance from the plasmonexciting part 841. The shapes and locations of the first and second sidewall parts 84A1 and 84A2 are the same as those of the first and second sidewall parts 34A1 and 34A2 of the first embodiment. - The
plasmon generator 84 further has an extended portion 84B and an extended portion 84C. The extended portion 84B is connected to an edge of the first sidewall part 84A1 opposite from the plasmonexciting part 841. The extended portion 84C is connected to an edge of the second sidewall part 84A2 opposite from the plasmonexciting part 841. From the edge of the first sidewall part 84A1 opposite from the plasmonexciting part 841, the extended portion 84B extends parallel to the evanescentlight generating surface 32 c and away from both the first and second sidewall parts 84A1 and 84A2. From the edge of the second sidewall part 84A2 opposite from the plasmonexciting part 841, the extended portion 84C extends parallel to the evanescentlight generating surface 32 c and away from both the first and second sidewall parts 84A1 and 84A2. Each of the extended portions 84B and 84C has a constant width in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) regardless of the distance from themedium facing surface 12 a. In the example shown inFIG. 22 , the width of the extended portion 84B is greater than that of the extended portion 84C. Note that theplasmon generator 84 need not necessarily have the extended portion 84C. - The plasmon
exciting part 841 includes apropagative edge 841 a that lies at an end of the connected first and second sidewall parts 84A1 and 84A2 closer to the evanescentlight generating surface 32 c. The shape and location of thepropagative edge 841 a are the same as those of thepropagative edge 341 a of the first embodiment. - The front end face 842 has a first portion 842 a and a second portion 842 b that lie at respective ends of the first and second sidewall parts 84A1 and 84A2 and are connected to each other into a V-shape, a third portion 842 c that lies at an end of the extended portion 84B, a fourth portion 842 d that lies at an end of the extended portion 84C, and a near-field
light generating edge 842 e that lies at an end of the plasmon exciting part 841 (propagative edge 841 a). The shape and location of the near-fieldlight generating edge 842 e are the same as those of the near-fieldlight generating edge 342 e of the first embodiment. - The thermally-assisted magnetic recording head further includes a
conductor 86 made of a conductive material. Theconductor 86 has a Seebeck coefficient different from that of theplasmon generator 84, and is in contact with theplasmon generator 84. As shown inFIG. 22 , theconductor 86 makes contact with theplasmon generator 84 at least on a virtual straight line L, the virtual straight line L passing through the near-fieldlight generating edge 842 e and extending in the direction perpendicular to the evanescentlight generating surface 32 c. In the present embodiment, in particular, theconductor 86 is disposed on the V-shaped portion 84A and the extended portions 84B and 84C of theplasmon generator 84 and makes contact with such portions. - As will be detailed later, in the present embodiment, heat absorption by the Peltier effect occurs in a contact area between the
plasmon generator 84 and theconductor 86 when a current is made to flow from one of theplasmon generator 84 and theconductor 86, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area. To increase the amount of heat absorption by the Peltier effect, it is preferred that the difference between the Seebeck coefficient of theplasmon generator 84 and that of theconductor 86 be as great as possible. The Seebeck coefficient of theplasmon generator 84 and that of theconductor 86 may have opposite signs. - For example, the
plasmon generator 84 may be made of Au, and the conductive material used to form theconductor 86 may contain at least one of Co, Ni, and a CuNi alloy. As described in a literature “Japanese Journal of Applied Physics, Vol. 44, No. 1, 2005, pp. L12-14,” Au has a Seebeck coefficient of 1.9 μV/K at 300 K, and Co has a Seebeck coefficient of −30.8 μV/K at 300 K. Theplasmon generator 84 made of Au thus has a Seebeck coefficient of 1.9 μV/K at 300 K. If theconductor 86 is made of Co, theconductor 86 has a Seebeck coefficient of −30.8 μV/K at 300K. The foregoing literature describes that cooling by the Peltier effect occurs at the Au—Co interface. Consequently, if theplasmon generator 84 is made of Au, Co is an appropriate conductive material for forming theconductor 86. Like Co, each of Ni and a CuNi alloy has a negative Seebeck coefficient of a high absolute value. If theplasmon generator 84 is made of Au, then Ni and a CuNi alloy are also appropriate as the conductive material for forming theconductor 86, aside from Co. When theplasmon generator 84 is made of Au, the conductive material used to form theconductor 86 may be an alloy that contains at least one of Co, Ni, and a CuNi alloy, and that is lower in Seebeck coefficient than Au. - Now, the dimension of the
conductor 86 on the virtual straight line L shown inFIG. 22 will be represented by the symbol D2. Too small D2 makes the resistance of theconductor 86 too high. Too large D2 hinders the effect of the embodiment that the position of occurrence of the write magnetic field and the position of occurrence of the near-field light can be located close to each other. In such a point of view, it is preferred that D2 fall within the range of 20 to 50 nm. - In the example shown in
FIG. 22 , theconductor 86 is greater than the V-shaped portion 84A of theplasmon generator 84 in dimension in the track width direction TW (Y direction) at themedium facing surface 12 a. The dimension of theconductor 86 in the track width direction TW is 0.6 μm, for example. In the example shown inFIG. 23 , theconductor 86 is greater than theplasmon generator 84 in length in the X direction. The length of theconductor 86 in the X direction is 1.2 μm, for example. - As shown in
FIG. 22 , theconductor 86 includes a V-shaped portion 86A that has an end face located in themedium facing surface 12 a. The V-shaped portion 86A is arranged along the inner surfaces of the V-shaped portion 84A of theplasmon generator 84 and extends in the direction perpendicular to themedium facing surface 12 a (X direction). The V-shaped portion 86A is V-shaped in cross section parallel to themedium facing surface 12 a. - The
conductor 86 further includes extended portions 86B and 86C that spread out from the top ends of the V-shaped portion 86A of theconductor 86 in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction). The extended portion 86B is arranged along the top surface of the extended portion 84B of theplasmon generator 84. The extended portion 86C is arranged along the top surface of the extended portion 84C of theplasmon generator 84 and thetop surface 33 a of the cladlayer 33. Each of the extended portions 86B and 86C has a constant width in the direction parallel to themedium facing surface 12 a and the evanescentlight generating surface 32 c (Y direction) regardless of the distance from themedium facing surface 12 a. In the example shown inFIG. 22 , the width of the extended portion 86B is smaller than that of the extended portion 84B of theplasmon generator 84. The width of the extended portion 86C is greater than that of the extended portion 86B and greater than that of the extended portion 84C of theplasmon generator 84. Note that theconductor 86 need not necessarily have the extended portion 86B. - The
magnetic pole 85 is disposed on theconductor 86 so that at least a part of theconductor 86, that is, the V-shaped portion 86A, is interposed between theplasmon generator 84 and themagnetic pole 85. Themagnetic pole 85 has afirst portion 85A and asecond portion 85B. Thesecond portion 85B is located farther from the evanescentlight generating surface 32 c of the core 32 than is thefirst portion 85A. InFIG. 22 andFIG. 23 , the border between thefirst portion 85A and thesecond portion 85B is shown by a chain double-dashed line. Thefirst portion 85A has a triangular-prism-shaped part in the vicinity of themedium facing surface 12 a. The triangular-prism-shaped part of thefirst portion 85A is interposed between the first and second sidewall parts 84A1 and 84A2 of theplasmon generator 84. The V-shaped portion 86A of theconductor 86 is interposed between the triangular-prism-shaped part of thefirst portion 85A and the first and second sidewall parts 84A1 and 84A2. - As shown in
FIG. 22 , themagnetic pole 85 has an end face 851 located in themedium facing surface 12 a. The end face 851 includes a first portion 851 a and a second portion 851 b. The first portion 851 a is the end face of thefirst portion 85A. The second portion 851 b is the end face of thesecond portion 85B. The first portion 851 a has a triangular shape and is interposed between the first and second portions 842 a and 842 b of the front end face 842 of theplasmon generator 84. The end face of the V-shaped portion 86A of theconductor 86 is interposed between the first portion 851 a and the first and second portions 842 a and 842 b of the front end face 842. The end face 851 a has atip 851 c located at its bottom end. - The thermally-assisted magnetic recording head further includes a
first electrode 87 that is electrically connected to the extended portion 84B of theplasmon generator 84, and asecond electrode 88 that is electrically connected to the extended portion 86C of theconductor 86. The first andsecond electrodes magnetic pole 85 in the track width direction TW, each at a distance from themagnetic pole 85. Not-shown leads are connected to the first andsecond electrodes second electrodes second electrodes magnetic pole 85. - The thermally-assisted magnetic recording head further includes insulating
films films plasmon generator 84 and theconductor 86 that are interposed between themagnetic pole 85 and the first andsecond electrodes films medium facing surface 12 a (X direction). The insulatingfilms films - Reference is now made to
FIG. 24A toFIG. 26A ,FIG. 24B toFIG. 26B , andFIG. 27 toFIG. 29 to describe an example of the method of forming theplasmon generator 84, themagnetic pole 85 and theconductor 86.FIG. 24A toFIG. 26A are plan views each showing a part of a stack of layers fabricated in the process of forming theplasmon generator 84, themagnetic pole 85 and theconductor 86.FIG. 24B toFIG. 26B , andFIG. 27 toFIG. 29 are cross-sectional views each showing a part of the stack of layers fabricated in the process of forming theplasmon generator 84, themagnetic pole 85 and theconductor 86. InFIG. 24A toFIG. 26A , the symbol ABS indicates the position where themedium facing surface 12 a is to be formed.FIG. 24B toFIG. 26B , andFIG. 27 toFIG. 29 each show a cross section in the position ABS. - The method of forming the
plasmon generator 84, themagnetic pole 85 and theconductor 86 is the same as in the first embodiment up to the step of forming theclad layer 33 as shown inFIG. 13 . -
FIG. 24A andFIG. 24B show the next step. In this step, a metal film that is to become theplasmon generator 84 later is initially formed by, for example, sputtering, so as to cover the entire top surface of the stack shown inFIG. 13 . Next, the metal film is patterned by etching a part of the metal film by ion milling, for example. As a result, the remaining metal film becomes theplasmon generator 84. -
FIG. 25A andFIG. 25B show the next step. In this step, theconductor 86 is formed by lift-off, for example. Where theconductor 86 is formed by lift-off, a mask having an opening that has a shape corresponding to the planar shape of theconductor 86 to be formed later is initially formed. The mask can be formed by patterning a photoresist layer by photolithography, for example. With the mask left intact, a metal film to become theconductor 86 later is then formed by, for example, sputtering, so as to cover the entire top surface of the stack shown inFIG. 24A andFIG. 24B . Next, the mask is lifted off. The remaining metal film thereby becomes theconductor 86. -
FIG. 26A andFIG. 26B show the next step. In this step, the insulatinglayers plasmon generator 84 and theconductor 86. -
FIG. 27 shows the next step. In this step, anelectrode film 89 is formed by, for example, sputtering, so as to cover the entire top surface of the stack shown inFIG. 26A andFIG. 26B . The material of theelectrode film 89 is FeCo, for example. -
FIG. 28 shows the next step. In this step, platingfilms electrode film 89 as the electrode. Theplating film 85C has a shape corresponding to the planar shape of thesecond portion 85B of themagnetic pole 85. Theplating film 87C has a shape corresponding to the planar shape of thefirst electrode 87. Theplating film 88C has a shape corresponding to the planar shape of thesecond electrode 88. Theplating film 85C is formed also on a part of theelectrode film 89 located on the insulatingfilm 81 and on a part of theelectrode film 89 located on the insulatingfilm 82. Theplating film 87C is formed also on a part of theelectrode film 89 located on the insulatingfilm 81. Theplating film 88C is formed also on a part of theelectrode film 89 located on the insulatingfilm 82. -
FIG. 29 shows the next step. In this step, theelectrode film 89 is etched by, for example, ion milling, using the platingfilms top surface 33 a of the cladlayer 33 and the top surfaces of the insulatingfilms plating film 85C and afirst portion 89A of theelectrode film 89 that remains below theplating film 85C form themagnetic pole 85. Theplating film 87C and asecond portion 89B of theelectrode film 89 that remains below theplating film 87C form thefirst electrode 87. Theplating film 88C and athird portion 89C of theelectrode film 89 that remains below theplating film 88C form thesecond electrode 88. The insulatingfilms plasmon generator 84 and theconductor 86 interposed between themagnetic pole 85 and the first andsecond electrodes electrode film 89. - The
magnetic pole 85, thefirst electrode 87 and thesecond electrode 88 are formed simultaneously in the steps shown inFIG. 27 toFIG. 29 . However, the formation of themagnetic pole 85 and the formation of the first andsecond electrodes - The operation and effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. The thermally-assisted magnetic recording head according to the present embodiment includes the
conductor 86 made of a conductive material, theconductor 86 having a Seebeck coefficient different from that of theplasmon generator 84 and being in contact with theplasmon generator 84. In the present embodiment, heat absorption by the Peltier effect occurs in the contact area between theplasmon generator 84 and theconductor 86 when a current is made to flow from one of theplasmon generator 84 and theconductor 86, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area. A voltage for generating the current that causes the heat absorption by the Peltier effect in the contact area is applied to the first andsecond electrodes plasmon generator 84 is made of Au and theconductor 86 is made of Co, the current is passed through thesecond electrode 88, theconductor 86, theplasmon generator 84, and thefirst electrode 87 in this order. According to the present embodiment, it is thereby possible to cool theplasmon generator 84. - Now, the amount of heat absorption by the Peltier effect in the contact area between the
plasmon generator 84 and theconductor 86 will be specifically described. Here, a description will be given for the case where theplasmon generator 84 is made of Au and theconductor 86 is made of Co. The amount of heat absorption Q per unit time at the contact area is given by the following equation (1): -
Q=π AB ×I (1) - Here, πAB is the Peltier coefficient, and I is the current that passes through the contact area. The Peltier coefficient πAB is given by the following equation (2):
-
πAB=(αA−αB)×T (2) - Here, αA is the Seebeck coefficient of the plasmon generator 84 (Au), and αB is the Seebeck coefficient of the conductor 86 (Co). T is the absolute temperature. As mentioned previously, Au has a Seebeck coefficient of 1.9 μV/K at 300 K, and Co has a Seebeck coefficient of −30.8 μV/K at 300 K. The Peltier coefficient πAB at 300 K is thus (1.9−(−30.8))×300=9810 μV=9.81 mV.
- As can be seen from the foregoing equations (1) and (2), when the Peltier coefficient πAB is not zero, i.e., when the
plasmon generator 84 and theconductor 86 have different Seebeck coefficients, it is possible to cause heat absorption by the Peltier effect in the contact area between theplasmon generator 84 and theconductor 86 by making a current to flow from one of theplasmon generator 84 and theconductor 86, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area. Consequently, it is possible to cool theplasmon generator 84 by the Peltier effect. According to the present embodiment, the cooling operation by the Peltier effect is added to the heat dissipating operation by the extended portions 84B and 84C of theplasmon generator 84. This allows a further suppression of a rise in temperature of theplasmon generator 84. - In the present embodiment, the
first electrode 87 is in contact with the extended portion 84B of theplasmon generator 84, and thesecond electrode 88 is in contact with the extended portion 84C of theconductor 86. Consequently, according to the present embodiment, the heat generated in theplasmon generator 84 can be dissipated through thefirst electrode 87, and through theconductor 86 and thesecond electrode 88. - The remainder of configuration, function and effects of the present embodiment are similar to those of the first embodiment.
- A fourth embodiment of the invention will now be described with reference to
FIG. 30 .FIG. 30 is a front view showing a part of the medium facing surface of the head unit of the thermally-assisted magnetic recording head according to the present embodiment. The thermally-assisted magnetic recording head according to the present embodiment does not have the first andsecond electrodes plasmon generator 94, amagnetic pole 95, aconductor 96, and insulatingfilms plasmon generator 84, themagnetic pole 85, theconductor 86, and the insulatingfilms plasmon generator 94 is made of the same material as that of theplasmon generator 84 of the third embodiment. Themagnetic pole 95 is made of the same material as that of themagnetic pole 85 of the third embodiment. Theconductor 96 is made of the same material as that of theconductor 86 of the third embodiment. The insulatingfilms films - The
plasmon generator 94 has an outer surface that includes a plasmonexciting part 941 and afront end face 942. The plasmonexciting part 941 faces the evanescentlight generating surface 32 c of the core 32 with a predetermined distance therebetween. Thefront end face 942 is located in themedium facing surface 12 a. Theplasmon generator 94 further has a V-shapedportion 94A that has an end face located in themedium facing surface 12 a. The V-shapedportion 94A has a first sidewall part 94A1 and a second sidewall part 94A2 that are each connected to the plasmonexciting part 941, and that increase in distance from each other with increasing distance from the plasmonexciting part 941. The shapes and locations of the first and second sidewall parts 94A1 and 94A2 are the same as those of the first and second sidewall parts 84A1 and 84A2 of the third embodiment. - The
plasmon generator 94 further has an extendedportion 94B and anextended portion 94C. Theextended portion 94B is connected to an edge of the first sidewall part 94A1 opposite from the plasmonexciting part 941. Theextended portion 94C is connected to an edge of the second sidewall part 94A2 opposite from the plasmonexciting part 941. A not-shown lead is connected to theextended portion 94B. The shapes and locations of theextended portions plasmon generator 94 need not necessarily have the extendedportion 94C. - The
front end face 942 has afirst portion 942 a and asecond portion 942 b that lie at respective ends of the first and second sidewall parts 94A1 and 94A2 and are connected to each other into a V-shape, athird portion 942 c that lies at an end of theextended portion 94B, afourth portion 942 d that lies at an end of theextended portion 94C, and a near-fieldlight generating edge 942 e that lies at an end of the plasmonexciting part 941. The shape and location of the near-fieldlight generating edge 942 e are the same as those of the near-fieldlight generating edge 842 e of the third embodiment. - The insulating
film 91 is arranged along the inner surface of the first sidewall part 94A1 and the top surface of theextended portion 94B of theplasmon generator 94, and covers the joint between the first sidewall part 94A1 and theextended portion 94B and its vicinity. The insulatingfilm 92 is arranged along the inner surface of the second sidewall part 94A2 and the top surface of theextended portion 94C of theplasmon generator 94, and covers the joint between the second sidewall part 94A2 and theextended portion 94C and its vicinity. - As shown in
FIG. 30 , theconductor 96 is arranged along the inner surfaces of the V-shapedportion 94A and the top surfaces of the insulatingfilms conductor 96 makes contact with theplasmon generator 94 at least on a virtual straight line L, the virtual straight line L passing through the near-fieldlight generating edge 942 e and extending in the direction perpendicular to the evanescentlight generating surface 32 c. In the present embodiment, theconductor 96 makes contact with theplasmon generator 94 on the virtual straight line L passing through the near-fieldlight generating edge 942 e and extending in the direction perpendicular to the evanescentlight generating surface 32 c, and in the vicinity of the virtual straight line L. - The
magnetic pole 95 is disposed on theconductor 96 so that theconductor 96 is interposed between theplasmon generator 94 and themagnetic pole 95. Themagnetic pole 95 has a portion interposed between the first and second sidewall parts 94A1 and 94A2 of theplasmon generator 94. Between this portion of themagnetic pole 95 and the first and second sidewall parts 94A1 and 94A2, there are interposed respective portions of theconductor 96 and the insulatingfilms magnetic pole 95 has anend face 951 located in themedium facing surface 12 a. Theend face 951 has a portion interposed between the first andsecond portions front end face 942 of theplasmon generator 94. Between this portion of theend face 951 and the first andsecond portions conductor 96 and the insulatingfilms medium facing surface 12 a. Theend face 951 has atip 951 c located at its bottom end. A not-shown lead is connected to themagnetic pole 95. - The
conductor 96 is electrically connected to themagnetic pole 95. Themagnetic pole 95 is formed by frame plating, for example. Theconductor 96 may be used as an electrode film when forming themagnetic pole 95 by frame plating. - The operation and effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. In the present embodiment, as shown in
FIG. 30 , theconductor 96 makes contact with theplasmon generator 94 at least on the virtual straight line L that passes through the near-fieldlight generating edge 942 e and extends in the direction perpendicular to the evanescentlight generating surface 32 c. In the present embodiment, as in the third embodiment, heat absorption by the Peltier effect occurs in the contact area between theplasmon generator 94 and theconductor 96 when a current is made to flow from one of theplasmon generator 94 and theconductor 96, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area. In the present embodiment, theconductor 96 is electrically connected to themagnetic pole 95. A voltage for generating the current that causes the heat absorption by the Peltier effect in the contact area is applied to theplasmon generator 94 and themagnetic pole 95. According to the present embodiment, it is thereby possible to cool theplasmon generator 94. - In the present embodiment, the insulating
films plasmon generator 94 from part of theconductor 96 so that the contact area between theplasmon generator 94 and theconductor 96 is formed in a limited area close to the near-fieldlight generating edge 942 e. According to the present embodiment, it is therefore possible to cause the heat absorption by the Peltier effect in proximity to the near-fieldlight generating edge 942 e where theplasmon generator 94 becomes highest in temperature. Consequently, according to the present embodiment, the near-fieldlight generating edge 942 e of theplasmon generator 94 can be cooled more efficiently as compared with the case where the contact area between theplasmon generator 94 and theconductor 96 has a greater area than in the embodiment, provided that the amount of heat absorption by the Peltier effect is the same. As a result, it is possible to suppress a rise in temperature of the near-fieldlight generating edge 942 e where theplasmon generator 94 becomes highest in temperature. - The remainder of configuration, function and effects of the present embodiment are similar to those of the third embodiment.
- The present invention is not limited to the foregoing embodiments, and various modifications may be made thereto. For example, in the third and fourth embodiments, the plasmon generator may have the same configuration as that of the
plasmon generator 34 of the second embodiment. - It is apparent that the present invention can be carried out in various forms and modifications in the light of the foregoing descriptions. Accordingly, within the scope of the following claims and equivalents thereof, the present invention can be carried out in forms other than the foregoing most preferable embodiments.
Claims (16)
1. A thermally-assisted magnetic recording head comprising:
a medium facing surface that faces a magnetic recording medium;
a magnetic pole that has an end face located in the medium facing surface and produces a write magnetic field for writing data on the magnetic recording medium;
a waveguide including a core and a clad, the core propagating light; and
a plasmon generator, wherein:
the core has an evanescent light generating surface that generates evanescent light based on the light propagated through the core;
the plasmon generator has an outer surface, the outer surface including: a plasmon exciting part that faces the evanescent light generating surface with a predetermined distance therebetween; and a front end face located in the medium facing surface;
the plasmon generator has: a first sidewall part and a second sidewall part that are each connected to the plasmon exciting part, the first and second sidewall parts increasing in distance from each other with increasing distance from the plasmon exciting part; and at least one extended portion that is connected to an edge of at least one of the first and second sidewall parts, the edge being opposite from the plasmon exciting part;
from the edge of the at least one of the first and second sidewall parts opposite from the plasmon exciting part, the at least one extended portion extends parallel to the evanescent light generating surface and away from both the first and second sidewall parts;
the magnetic pole has a portion interposed between the first and second sidewall parts;
the front end face includes: a first portion and a second portion that lie at respective ends of the first and second sidewall parts and are connected to each other into a V-shape; at least one third portion that lies at an end of the at least one extended portion; and a near-field light generating edge that lies at an end of the plasmon exciting part;
the end face of the magnetic pole has a portion interposed between the first and second portions of the front end face;
a surface plasmon is excited on the plasmon exciting part through coupling with the evanescent light generated from the evanescent light generating surface; and
the near-field light generating edge generates near-field light based on the surface plasmon excited on the plasmon exciting part.
2. The thermally-assisted magnetic recording head according to claim 1 , wherein the magnetic pole is in contact with the plasmon generator.
3. The thermally-assisted magnetic recording head according to claim 1 , wherein:
the first and second sidewall parts are connected to each other so that the connected first and second sidewall parts have a V-shaped cross section parallel to the medium facing surface;
the plasmon exciting part includes a propagative edge that lies at an end of the connected first and second sidewall parts closer to the evanescent light generating surface; and
the near-field light generating edge lies at an end of the propagative edge.
4. The thermally-assisted magnetic recording head according to claim 1 , wherein:
the plasmon generator further has a bottom part that is shaped like a plate and connects the first and second sidewall parts to each other at their respective edges closer to the evanescent light generating surface;
the plasmon exciting part includes a flat surface part that is formed by a surface of the bottom part that is closer to the evanescent light generating surface; and
the flat surface part includes a width changing portion, the width changing portion having a width that decreases with decreasing distance to the medium facing surface, the width being in a direction parallel to the medium facing surface and the evanescent light generating surface.
5. The thermally-assisted magnetic recording head according to claim 1 , further comprising a buffer part that is located between the evanescent light generating surface and the plasmon exciting part and has a refractive index lower than that of the core.
6. The thermally-assisted magnetic recording head according to claim 1 , wherein a dimension of the first and second sidewall parts in a direction perpendicular to the evanescent light generating surface falls within a range of 200 to 400 nm.
7. The thermally-assisted magnetic recording head according to claim 1 , wherein a dimension of the front end face on a virtual straight line that passes through the near-field light generating edge and extends in a direction perpendicular to the evanescent light generating surface falls within a range of 20 to 70 nm.
8. The thermally-assisted magnetic recording head according to claim 1 , further comprising a conductor made of a conductive material, the conductor having a Seebeck coefficient different from that of the plasmon generator and being in contact with the plasmon generator,
wherein heat absorption by the Peltier effect occurs in a contact area between the plasmon generator and the conductor when a current is made to flow from one of the plasmon generator and the conductor, the one being lower in Seebeck coefficient, to the other which is higher in Seebeck coefficient, through the contact area.
9. The thermally-assisted magnetic recording head according to claim 8 , wherein the plasmon generator is made of Au, and the conductive material contains at least one of Co, Ni, and a CuNi alloy.
10. The thermally-assisted magnetic recording head according to claim 8 , wherein the conductor is in contact with the plasmon generator on at least a virtual straight line that passes through the near-field light generating edge and extends in a direction perpendicular to the evanescent light generating surface.
11. The thermally-assisted magnetic recording head according to claim 10, wherein a dimension of the conductor on the virtual straight line falls within a range of 20 to 50 nm.
12. The thermally-assisted magnetic recording head according to claim 8 , wherein at least part of the conductor is interposed between the plasmon generator and the magnetic pole.
13. The thermally-assisted magnetic recording head according to claim 8 , further comprising a first electrode that is electrically connected to the plasmon generator and a second electrode that is electrically connected to the conductor, wherein a voltage for generating the current is applied to the first and second electrodes.
14. The thermally-assisted magnetic recording head according to claim 8 , wherein the conductor is electrically connected to the magnetic pole, and a voltage for generating the current is applied to the plasmon generator and the magnetic pole.
15. A head gimbal assembly comprising: the thermally-assisted magnetic recording head according to claim 1 ; and a suspension that supports the thermally-assisted magnetic recording head.
16. A magnetic recording device comprising: a magnetic recording medium; the thermally-assisted magnetic recording head according to claim 1 ; and a positioning device that supports the thermally-assisted magnetic recording head and positions the thermally-assisted magnetic recording head with respect to the magnetic recording medium.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/823,491 US8077559B1 (en) | 2010-06-25 | 2010-06-25 | Thermally-assisted magnetic recording head including plasmon generator |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/823,491 US8077559B1 (en) | 2010-06-25 | 2010-06-25 | Thermally-assisted magnetic recording head including plasmon generator |
Publications (2)
Publication Number | Publication Date |
---|---|
US8077559B1 US8077559B1 (en) | 2011-12-13 |
US20110317528A1 true US20110317528A1 (en) | 2011-12-29 |
Family
ID=45092715
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/823,491 Active 2030-08-03 US8077559B1 (en) | 2010-06-25 | 2010-06-25 | Thermally-assisted magnetic recording head including plasmon generator |
Country Status (1)
Country | Link |
---|---|
US (1) | US8077559B1 (en) |
Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20120075967A1 (en) * | 2010-09-28 | 2012-03-29 | Tdk Corporation | Thermally assisted magnetic recording head |
US20120147716A1 (en) * | 2010-12-08 | 2012-06-14 | Tdk Corporation | Thermally-assisted magnetic head |
US20120213041A1 (en) * | 2011-02-17 | 2012-08-23 | Tdk Corporation | Heat-assisted magnetic write head, head gimbals assembly, head arm assembly, and magnetic disk device |
US20120230168A1 (en) * | 2011-03-11 | 2012-09-13 | Tdk Corporation | Heat-assisted magnetic write head, head gimbals assembly, head arm assembly, and magnetic disk device |
US20130176836A1 (en) * | 2012-01-06 | 2013-07-11 | University Of Southampton | Magnetic field generator |
US8801945B2 (en) * | 2012-11-13 | 2014-08-12 | Sae Magnetics (H.K.) Ltd. | Write element, thermally assisted magnetic head slider, head gimbal assembly, hard disk drive with the same, and manufacturing method thereof |
US8830800B1 (en) * | 2013-06-21 | 2014-09-09 | Seagate Technology Llc | Magnetic devices including film structures |
US9275833B2 (en) | 2012-02-03 | 2016-03-01 | Seagate Technology Llc | Methods of forming layers |
US9280989B2 (en) | 2013-06-21 | 2016-03-08 | Seagate Technology Llc | Magnetic devices including near field transducer |
US9672848B2 (en) | 2015-05-28 | 2017-06-06 | Seagate Technology Llc | Multipiece near field transducers (NFTS) |
US9824709B2 (en) | 2015-05-28 | 2017-11-21 | Seagate Technology Llc | Near field transducers (NFTS) including barrier layer and methods of forming |
US10032468B1 (en) | 2015-11-06 | 2018-07-24 | Seagate Technology Llc | Heat-assisted magnetic recording head configured to conduct heat away from slider components to a substrate |
US10049693B2 (en) * | 2016-08-03 | 2018-08-14 | Seagate Technology Llc | Substrate heat channels for heat assisted magnetic recording for reader over writer transducer application |
US10074386B1 (en) | 2015-05-19 | 2018-09-11 | Seagate Technology Llc | Magnetic writer coil incorporating integral cooling fins |
US10192573B2 (en) | 2015-03-22 | 2019-01-29 | Seagate Technology Llc | Devices including metal layer |
Families Citing this family (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4518158B2 (en) * | 2008-02-08 | 2010-08-04 | Tdk株式会社 | Thermally assisted magnetic head, head gimbal assembly, and hard disk drive |
US8374062B2 (en) * | 2010-09-23 | 2013-02-12 | Tdk Corporation | Heat assist magnetic write head, head gimbals assembly, head arm assembly, and magnetic disk device |
US8437230B2 (en) * | 2011-02-18 | 2013-05-07 | Tdk Corporation | Heat-assisted magnetic write head, head gimbals assembly, head arm assembly, and magnetic disk device |
US8264920B1 (en) * | 2011-07-27 | 2012-09-11 | Tdk Corporation | Near-field light generator and thermally-assisted magnetic recording head |
US8400884B1 (en) * | 2012-01-19 | 2013-03-19 | Headway Technologies, Inc. | Method of manufacturing plasmon generator |
JP5762987B2 |