JP2009059441A - Optically-assisted magnetic head device, optically-assisted magnetic recording device, and optically-assisted magnetic recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a light spot and arrange a magnetic pole generating a recording magnetic field in proximity to the light spot in the order of 10 nm. <P>SOLUTION: The optically-assisted magnetic head device includes a condensing optical system 4 and a thin-film magnetic head 5. The condensing optical system 4 includes an SIL 2. A main magnetic pole 21 of the thin-film magnetic head 5 is constituted so that a side surface 21S at an inflow end side in a relative traveling (arrow M) with a magnetic recording medium is along an optical axis C of the condensing optical system 4, and the optical axis C is disposed at the central part of the side surface 21S. The light condensed at the central part of the side surface 21S of the main magnetic pole 21 by the condensing optical system 4 is converted into linearly polarized light, and its electric field vibration direction (arrow P) is arranged along the relative traveling direction with the magnetic recording medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optically assisted magnetic head device, an optically assisted magnetic recording device, and an optically assisted magnetic recording method that perform magnetic recording by locally irradiating a recording area with light.

There is an increasing demand for high-density recording on information recording media. Even in information recording on magnetic recording media such as magnetic tapes and magnetic disks, ultra-high density recording is required. In this case, perpendicular recording is employed to make the recording pits smaller, and development is being carried out to achieve high resolution and to increase the coercivity of the magnetic layer.
At present, a magnetic body having a high coercive force is being developed, but it is difficult to sufficiently increase the signal recording magnetic field when recording is performed on a magnetic recording medium made of a material having such a high coercive force. In order to solve this problem, an optically assisted magnetic head device has been proposed. This optically assisted magnetic head apparatus performs magnetic recording by locally raising the temperature of a recording portion of a magnetic recording medium by light irradiation and temporarily reducing the coercivity of the recording area. As a result, it is possible to record information on a magnetic recording medium having a magnetic layer having a high coercive force by a minute magnetic field spot.

In such optically assisted magnetic recording, it is necessary to increase the recording density, that is, to reduce the light spot in order to form a minute recording bit. In a normal condensing lens, the spot diameter is determined by the wavelength of light used and the numerical aperture (NA) of the lens. However, the numerical aperture is limited, which limits the miniaturization of the spot diameter.
On the other hand, a hemispherical or super-hemispherical solid immersion lens (Solid Immersion Lens, hereinafter referred to as SIL) is interposed between the objective lens and the recording medium, thereby the numerical aperture of the objective lens. A method for improving the above has been developed. When a spot by near-field light is formed using a hemispherical or super hemispherical SIL, the spot diameter can be reduced. When the refractive index of the SIL for the wavelength of light used is n, n times in the case of hemispherical SIL, it is possible to increase the effective numerical aperture n ² times in the case of hyper-hemispherical SIL (also referred to as super-SIL), That is, the spot size is reduced to 1 / n and 1 / n ² , respectively.

Focusing on such spot miniaturization, an optically assisted magnetic head using a hemispherical or super hemispherical SIL has also been proposed (see, for example, Patent Document 1).
The optically assisted magnetic head described in Patent Document 1 has a two-group condensing lens system composed of an objective lens and a hemispherical or super hemispherical SIL. In particular, the SIL includes a spherical lens body, a light-transmitting substrate, Are formed by joining and integrating. A thin film magnetic head is formed on the light transmissive substrate to constitute a light-assisted magnetic head.
JP 2006-286119 A

In the above-described optically assisted magnetic head device, it is necessary to make the magnetic spot that generates the recording magnetic field and the optical spot that heats the surface of the magnetic recording medium close to the order of 10 nm, that is, less than 100 nm, simultaneously with the miniaturization of the optical spot. is there.
As a conventional optically assisted magnetic head, a method of forming an optical spot using an optical waveguide has been mainly studied, but in order to obtain sufficient light transmission efficiency in the waveguide, the thickness of the cladding layer is set to a wavelength. Therefore, it is not easy to place the light spot closer to the magnetic pole than this.

On the other hand, in an optically assisted magnetic head using a hemispherical or super hemispherical SIL such as the invention disclosed in Patent Document 1, the magnetic pole and the optical spot can be arranged close to each other. Moreover, when using a lens, since light is irradiated three-dimensionally, there is an advantage that the light use efficiency is high.
However, when the light spot is close to the magnetic pole in this way, there arises a problem that light is shielded by the magnetic pole. Therefore, a method for generating a sufficient recording magnetic field on the surface of the magnetic recording medium and realizing light irradiation with sufficient intensity is required.

  In view of the above problems, an object of the present invention is to miniaturize a light spot and to dispose a magnetic pole that generates a recording magnetic field and a light spot close to less than 100 nm.

  In order to solve the above problems, an optically assisted magnetic head device according to the present invention includes a condensing optical system and a thin film magnetic head, and the condensing optical system includes a hemispherical lens or a super hemispherical lens. The main magnetic pole of the thin film magnetic head has a configuration in which the side surface on the inflow end side relative to the magnetic recording medium is along the optical axis of the condensing optical system and the optical axis is arranged at the center of this side surface. . Further, the light condensed on the central portion of the side surface of the main magnetic pole by the condensing optical system is linearly polarized, and the electric field vibration direction is arranged along the traveling direction relative to the magnetic recording medium.

  The optically assisted magnetic recording apparatus according to the present invention includes the above-described optically assisted magnetic recording apparatus according to the present invention. That is, it includes a light source unit, a magnetic recording medium placement unit, a thin film magnetic head, a recording signal control unit, and a condensing optical system that guides light from the light source unit to the thin film magnetic head. The condensing optical system includes a hemispherical lens or a super hemispherical lens. In the main magnetic pole of the thin film magnetic head, the side surface on the inflow end side relative to the magnetic recording medium is along the optical axis of the condensing optical system, and the optical axis is arranged at the center of the side surface. Further, the light condensed on the central portion of the side surface of the main pole by the condensing optical system is linearly polarized, and the electric field vibration direction is arranged along the relative traveling direction with respect to the magnetic recording medium. .

  In the optically assisted magnetic recording method according to the present invention, a single magnetic pole type thin film magnetic head is disposed at a condensing spot position of a condensing optical system, and the main magnetic pole of the thin film magnetic head is relative to the magnetic recording medium. The side surface on the inflow end side in traveling is along the optical axis of the condensing optical system, and the optical axis is arranged at the center of the side surface. By the condensing optical system, linearly polarized light whose direction of electric field vibration is along the traveling direction relative to the magnetic field is incident on the main pole, and near-field light is generated from the tip position along the optical axis of the main pole. Recording is performed on a magnetic recording medium.

As described above, in the optically assisted magnetic head device, the optically assisted magnetic recording device, and the optically assisted magnetic recording method of the present invention, the main pole of the thin film magnetic head is used as the inflow end relative to the magnetic recording medium. The side surface on the side is along the optical axis of the condensing optical system, and the optical axis is arranged at the center of the side surface. The light collected by the condensing optical system at the center of the side surface of the main pole is linearly polarized, and the electric field vibration direction is arranged along the traveling direction relative to the magnetic recording medium to perform magnetic recording. To do.
In the case of such a configuration, as will be described later, it has been clarified that near-field light is generated at the inflow end of the main magnetic pole of the thin-film magnetic head and sufficiently high photoelectric field energy is obtained.
Therefore, by performing optically assisted magnetic recording using near-field light generated at the inflow end of the main magnetic pole, it is possible to realize the miniaturization of the light spot and the close arrangement of the magnetic pole and the light spot on the order of 10 nm.

  According to the present invention, the light spot can be miniaturized, and the magnetic pole for generating the recording magnetic field and the light spot can be arranged close to less than 100 nm.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
FIG. 1 is a schematic cross-sectional configuration diagram of an optically assisted magnetic head device according to an embodiment of the present invention. As shown in FIG. 1, the optically assisted magnetic head device in the present embodiment includes a condensing optical system 4 and a thin film magnetic head 5. The condensing optical system 4 includes an objective lens 3 and a hemispherical or super hemispherical SIL 2. The main magnetic pole 21 of the thin film magnetic head 5 is disposed such that the side surface 21S on the inflow end side relative to the magnetic recording medium (not shown) is along the optical axis C of the condensing optical system 4. In FIG. 1, the traveling direction of the magnetic recording medium is indicated by an arrow M. That is, the side surface 21S on the inflow end side of the main magnetic pole 21 is the side surface on the rear end side (left side in FIG. 1) of the arrow M in FIG. As shown in a schematic perspective configuration diagram of the main magnetic pole 2 in FIG. 2, the optical axis C is arranged at the center of the side surface 21 </ b> S of the main magnetic pole 21. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  1 and 2, the direction parallel to the traveling direction of the magnetic recording medium 11 is shown as the X axis, the direction along the optical axis is shown as the Z axis, and the direction perpendicular to these is shown as the Y axis. That is, the X direction is the relative running direction with respect to the magnetic recording medium, that is, the recording track length direction, the Y direction is the recording track width direction of the magnetic recording medium, and the Z direction is the gap direction in the SIL. In the present invention, the optical axis C is arranged at the center of the width in the Y direction of the side surface 21 </ b> S on the inflow end side of the main magnetic pole 21.

  In the optically assisted magnetic head according to the present embodiment, as shown in FIGS. 1 and 2, the light Li condensed on the central portion of the side surface 21S of the main magnetic pole 21 by the condensing optical system 4 is converted into linearly polarized light. To do. Furthermore, the electric field vibration direction is arranged along the traveling direction (arrow M) relative to the magnetic recording medium as indicated by arrow P. That is, in this case, the condensing optical system 4 and the thin film magnetic head 5 are arranged and configured so that the electric field vibration direction of the incident light Li is parallel to the recording track length direction of the magnetic recording medium.

  In FIG. 2, a surface H indicated by a two-dot chain line virtually indicates the same plane as the side surface 21 </ b> S on the inflow end side of the main magnetic pole 21. ) Is the inflow end side, and the region indicated by the arrow Fo (from the surface H to the main magnetic pole 21 side) is the outflow end side. FIG. 2 schematically shows the spot S by the light Li condensed by the condensing optical system 4.

  A more specific configuration example of the condensing optical system 4 in the optically assisted magnetic head shown in FIGS. 1 and 2 is shown in a schematic perspective configuration diagram of FIG. In FIG. 3, parts corresponding to those in FIG. As described above, in this example, the condensing optical system 4 includes the objective lens 3 and the hemispherical or super hemispherical SIL 2 used in the near-field optical recording. The objective lens 3 and the SIL 2 can realize an optical system that realizes a numerical aperture with an effective numerical aperture exceeding 1.0 and generates near-field light.

With a single objective lens, the focused spot diameter can only be reduced to about λ / NAobj due to the diffraction limit of light. Here, λ is the wavelength of the light used, and NAobj is the numerical aperture of the objective lens. On the other hand, as described above, in the condensing optical system 4 using the hemispherical or super hemispherical SIL2, the spot diameter is 1 / n in the hemispherical SIL on the bottom surface (focal plane) of the SIL2, and the super hemisphere. It can be miniaturized to 1 / n ² by the SIL of the mold. Here, n is the refractive index of SIL2 at the wavelength λ of the used light. Generally, by narrowing the gap (gap) between the bottom surface of the SIL 2 and the magnetic recording medium to λ / 10 or less, the spot diameter of λ / NAobj is further increased on the surface of the magnetic recording medium by the imaging action of near-field light. It is possible to reduce the size to 1 / n with a hemispherical SIL and 1 / n ² with a super hemispherical SIL.

  As shown in FIG. 3, in this example, the first and second optical blocks 6a and 6b and the spherical portion 2S are joined to form SIL2. The first and second optical blocks 6a and 6b and the spherical portion 2S are both made of an optical member having a light transmittance with respect to the wavelength of the used light and having a high refractive index, and preferably made of the same material. To do.

  An example of the manufacturing method of this SIL2 is demonstrated. For example, one end surface of the first optical block 6a is used as a head forming surface 6ah, and after the thin film magnetic head 5 is formed on the head forming surface 6ah, the second optical block 6b is bonded by sticking or welding with an optical adhesive. To do. The optical adhesive is preferably a high refractive index material having a refractive index of, for example, 1.5 or more, and more preferably the same refractive index as that of the first and second optical blocks 6a and 6b.

  The bonded first and second optical blocks 6a and 6b are subjected to depth polishing for adjusting the depth length of the main magnetic pole 21 by planar polishing the surface on the main magnetic pole forming side of the thin film magnetic head 5, The back surface is also polished to a predetermined thickness. On the other hand, a separate ball lens is prepared, and a part of the ball lens is polished to form a spherical portion 2S having a plane substantially orthogonal to the optical axis. As described above, the spherical portion 2S is preferably made of the same material as the first and second optical blocks 6a and 6b. Then, the plane of the spherical portion 2S is bonded to the bonding surfaces of the first and second optical blocks 6a and 6b by bonding, welding, or the like with the above-described optical adhesive. At this time, the main magnetic pole of the thin film magnetic head 5 formed in the first optical block 6a and the optical axis of the spherical portion 2S are positioned and joined so as to be in the arrangement described in FIG.

  SIL2 shown in FIG. 3 can be obtained by the manufacturing method described above. In the case of such a configuration, the spherical portion 2S and the spherical portion 2P included as a part in the first and second optical blocks 6a and 6b as shown by a broken line in FIG. Super hemispherical SIL2 is constructed. The plate thickness of the first and second optical blocks 6a and 6b and the thickness of the spherical portion 2S are selected so as to be hemispherical or super hemispherical as a whole. When the radius of the spherical portion 2S is r, the total thickness is r when the hemispherical SIL is used, and the total thickness is r × (1 + 1 / n) when the hemispherical SIL is used. Constitute. That is, when the thickness of the first and second optical blocks 6a and 6b after surface polishing is T, the thickness of the spherical portion 2S is formed by subtracting the thickness T from the final thickness.

  The total thickness of the SIL 2 having such a configuration is r in the case of a hemispherical type SIL, and r × (1 + 1 / n) in the case of a super hemispherical type SIL. It is completely equivalent to the type SIL. Therefore, the light condensed by the upper objective lens 3 is focused on the bottom surface of the synthesized SIL 2, that is, the surface on the recording medium side of the first and second blocks 6a and 6b, and functions as a normal SIL. Have By performing optical adjustment at the time of assembly, it is possible to position the optical axis center of the condensing optical system 4 on the head forming surface 6ah of the optical block 6a on which the main magnetic pole is formed. The center is disposed on the end face of the main pole.

  FIG. 4 is a schematic perspective configuration diagram of a part of an example of the condensing optical system 4 in which the objective lens 2 and the SIL 2 described in FIG. 4, portions corresponding to those in FIGS. 1 to 3 are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 4, the terminal lead-out portion 12 and the electrode 13 of the thin film magnetic head 5 may be formed on the head forming surface 6ah of the first optical block 6a. Note that the size and shape of the first and second optical blocks 6a and 6b are not limited to the examples shown in FIGS. 3 and 4, and may be various other shapes.

  FIG. 5 is an enlarged cross-sectional configuration diagram of an example of the thin film magnetic head 5. As shown in FIG. 5, in this case, an example of a single pole head structure for perpendicular recording is shown. The thin film magnetic head 5 is used for generating and applying a magnetic field to a recording section and a coil conductor 23 for generating a magnetic field. The main magnetic pole 21 is used. Although not shown in FIG. 5, a structure in which the sub magnetic pole is connected to the main magnetic pole to form a magnetic circuit may be used. In actual recording, the magnetic recording medium having the recording layer and the soft magnetic layer is opposed to the soft magnetic layer, and the main magnetic pole 21 and the coil conductor 23 constitute a magnetic circuit in the thin film magnetic head 5.

  In this example, as shown in FIG. 5, the main magnetic pole 21 is formed with a predetermined length on the head forming surface 6ah of the first optical block 6a, and the lower coil layer 23A and the insulating layer are interposed via the insulating layer 22. 24, a yoke 25 connected to the main magnetic pole 21, an insulating layer 26, and an upper coil layer 23B are formed, and the second optical block 6b is joined via an optical adhesive 27.

  6A and 6B show a schematic cross-sectional configuration diagram and a plan configuration diagram of an example of the thin-film magnetic head 5. 6A and 6B, parts corresponding to those in FIG. As shown in FIG. 6B, the coil conductor 23 of the thin film magnetic head 5 may be composed of a lower coil layer 23A, an upper coil layer 23B, and a connecting portion 23C that connect them, which are arranged in oblique directions opposite to each other. it can. In FIG. 6B, the terminal lead-out portion 12 extends from the lower coil layer 23A at both ends, but the number of turns of the coil, the configuration of each portion, the shape of each coil layer, etc. are not limited to this, and various modifications are possible. Needless to say. In FIG. 6B, the depth of the main magnetic pole 21 is indicated by ld, and the width of the main magnetic pole 21 and the yoke 25 in the direction orthogonal to the relative running direction with respect to the magnetic recording medium are indicated by wm and wy, respectively.

FIG. 7 is a schematic configuration diagram of the optically assisted magnetic recording apparatus according to the embodiment of the present invention.
The magnetic recording apparatus 100 according to the present embodiment includes a light source unit, for example, a light source unit 62 having a semiconductor laser element having a wavelength of 400 nm, an optically assisted magnetic head device 10 according to the present invention, and a magnetic recording medium 11, for example, a magnetic disk. A recording signal power supply unit that supplies a recording signal to the arrangement unit 64 of the magnetic recording medium 11 that is arranged and rotated and the magnetic head coil of the thin film magnetic head element 5 of the optically assisted magnetic head device 10, that is, a recording signal circuit 65. And an optical system 67 that introduces laser light from the light source unit 62 into the optically assisted magnetic head device 10 and introduces it into a light detection unit 66 having, for example, a photodiode that detects return light from the magnetic recording medium 11. Have The magnetic recording medium 11 is configured by sequentially laminating a soft magnetic layer 16 and a recording layer 17 on a substrate 15 such as glass.

  The optical system 67 includes, for example, a collimator lens (not shown), a beam splitter 68, and the like, as will be described in detail later with reference to FIG. Further, the detection output detected by the light detection unit 66 is calculated to obtain a desired servo signal for the optically assisted magnetic head device 10, for example, each servo signal such as focusing and tracking, and control for positioning for performing these controls. A device 69 is included. When the optically assisted magnetic head device 10 is mounted with a reproducing thin film magnetic head in addition to the thin film magnetic recording head, the head element is connected to a reproduction signal circuit (not shown) and performs a magnetic signal reproducing operation.

  In the magnetic recording medium placement unit 64, for example, the magnetic recording medium 11, which is a magnetic disk, is placed and rotated by a driving unit 80 such as a spindle motor as indicated by an arrow r, and the magnetic recording medium 11 is moved to an arrow M. It is rotated as shown in. The control mechanism 70 driven by the control device 69 can be constituted by, for example, a flying slider or a biaxial actuator described in FIG. The control mechanism 70 is equipped with the optically assisted magnetic head device 10 according to the present invention having the condensing optical system 4 and is driven based on the tracking servo signal and the gap servo signal to move the condensing optical system 4 in the tracking direction. It adjusts and moves and adjusts in the optical axis direction, that is, the gap direction.

  In the magnetic recording apparatus 100 of the present embodiment, the magnetic recording medium 11 is rotated, and a laser beam having a required wavelength, for example, 400 nm, is emitted from the light source unit 62 along the optical axis of the optically assisted magnetic head apparatus 10 by the optical system 67. The near-field light from this optically assisted magnetic head device 10 is introduced onto the magnetic recording medium 11. As will be described later, the optically assisted magnetic head device 10 has an arrangement configuration of a main magnetic pole and an optical axis, as will be described later, by means of a condensing optical system 4 having a two-group lens configuration with an objective lens 3 and a hemispherical or super hemispherical SIL2. In addition, by appropriately selecting the electric field vibration direction of the light incident by the condensing optical system 4, the spot diameter can be reduced and the center of the spot and the main magnetic pole can be arranged close to less than 100 nm.

  The spot is irradiated onto the rotating magnetic recording medium 11, and at the same time, an information recording signal is supplied to the magnetic head coil of the thin film magnetic head 5, so that the recording signal magnetic field from the tip of the main pole of the thin film magnetic head 5 Is applied to the magnetic recording medium 11 to record a signal.

  FIG. 8 is a side view of a section of the optically assisted magnetic head device 10 according to the present invention, in which a part of the control mechanism 70 for adjusting tracking and gap is formed as a floating slider. In FIG. 8, parts corresponding to those in FIG. In this floating type configuration, the slider 19 supported on the free end of the suspension 18 is mounted with the optically assisted magnetic head device 10 and floats by moving or rotating the magnetic recording medium 11 facing the thin film magnetic head 5. The gap between the optically assisted magnetic head device 10 and the magnetic recording medium 11 is adjusted by the flying height of 19.

  The magnetic recording apparatus 100 according to the present invention has a passive control type structure that floats by moving or rotating the magnetic recording medium 11 as described above, and controls the biaxial actuator or the like by the control apparatus 69 shown in FIG. It is of course possible to adopt a so-called active control type configuration that performs gap control and tracking of the assist type magnetic head device 10.

  FIG. 9 shows a schematic configuration diagram of an example of the magnetic recording apparatus 100 in this case. In this example, an example in which light of different wavelengths is used as light assist light and gap detection light during recording is shown. In this case, as shown in FIG. 9, a light source 30 and a collimating lens 31, a polarizing beam splitter 33, a beam expander 35, and a dichroic prism 45 are arranged on the outgoing light path. The dichroic prism 45 is configured to reflect light from the light source 30, and the condensing optical system 4 is disposed on the reflected light path. A light detection unit 39 such as a photodiode is disposed on the reflected light path of the return light of the polarization beam splitter 33 via the lens 38. A collimating lens 41, a beam splitter 42, a polarizing beam splitter 43, a ¼ wavelength plate 44, and a dichroic prism 45 are disposed on the outgoing light path of the other light source 40, and the condensing optical system 4 is disposed on the transmitted light path of the dichroic prism 45. Is placed. A light detection unit 51 such as a photodiode is disposed via a lens 50 on the reflected light path of the return light from the beam splitter 42.

  In such a configuration, the assisting light emitted from the light source 30 is converted into parallel light by the collimating lens 31, passes through the polarization beam splitter 33, and the beam width is adjusted by the beam expander 35. Further, the light is reflected by the dichroic prism 45 and is incident on the condensing optical system 4 mounted on the control mechanism 70 such as a biaxial actuator, that is, the objective lens 3 and the SIL 2.

  The magnetic recording medium 11 is rotated as indicated by an arrow r by a driving unit 80 such as a spindle motor. The relative traveling direction of the condensing optical system 4 with the SIL 2 is indicated by an arrow M. In the magnetic head device 10 of the present invention, the light assisting light applied to the magnetic recording medium 11 is linearly polarized light, and the electric field vibration direction is indicated by an arrow P. It arrange | positions so that it may become parallel.

  Tracking can also be performed using the return light of the light assist light. In this case, the return light reflected from the recording surface of the magnetic recording medium 11 is reflected by the dichroic prism 45 through the SIL 2 and the optical lens 3, reflected by the polarization beam splitter 33 through the beam expander 35, and by the lens 38. The light is collected by the light detection unit 39. A tracking signal or the like is obtained by the light detection unit 39. Based on this signal, a tracking control signal is generated by the control device 69 to drive a control mechanism 70 such as a biaxial actuator that holds the condensing optical system 4.

  On the other hand, the light from the light source 40 is irradiated to the dichroic prism 45 through the collimating lens 41, the beam splitter 42, the polarization beam splitter 43, and the quarter wavelength plate 44, and is combined with the light from the light source 30 in the dichroic prism 45. Then, the magnetic recording medium 11 is irradiated as a beam spot for gap detection via the objective lens 3 and SIL2. The return light of the gap detection beam spot from the magnetic recording medium 11 passes through the dichroic prism 45 and the quarter wavelength plate 44, and the light leaking from the polarization beam splitter 43 is reflected by the beam splitter 42 to pass through the lens 50. And detected by the light detection unit 51.

When the gap between the magnetic recording medium 11 and the SIL 2 is wide and light is substantially totally reflected at the SIL end face, the polarization changes on the SIL surface, so that part of the light leaks from the polarization beam splitter 43 in the return optical path. . On the other hand, when the magnetic recording medium 11 and the SIL 2 are close to each other and the near-field light leaks and is close to normal reflection, the amount of light leaking through the polarization beam splitter 43 is small because the change in polarization is small. Gap detection can be performed using this difference, that is, a change in the total reflected return light amount.
As a method for detecting the gap between SIL2 and the magnetic recording medium 11, various methods such as a method for detecting a change in capacitance can be employed.

Next, the light irradiation mode on the surface of the magnetic recording medium when the assisting light is irradiated onto the magnetic recording medium using the above-described magnetic recording apparatus will be described in more detail.
In this case, as shown in FIG. 10, the side surface 21 </ b> S on the inflow end side of the main magnetic pole 21 in the relative traveling direction M of the magnetic recording medium is arranged along the optical axis C. 10, parts corresponding to those in FIG. 2 and FIG. When the traveling direction of the incident light Li is the Z direction, the electric field vibration direction P is constant. In the present invention, the electric field vibration direction P is selected in the X direction, that is, the recording track length direction of the magnetic recording medium 11 which is the traveling direction M of the magnetic recording medium 11. As a result, spot formation at the end face 21T facing the magnetic recording medium of the main magnetic pole 21 and spot diameter reduction are realized.

  As described with reference to FIGS. 5 and 6, the thin film magnetic head including the main magnetic pole 21 in FIG. 10 is directly formed on the head forming surface of the optical block 6a such as glass on the left side in FIG. The tip 21T of the main magnetic pole 21, which is a recording magnetic field application unit, is disposed on the surface. In FIG. 10, the X direction is the stacking direction of the thin film magnetic heads, and the recording head and the reproducing head are arranged in series in this direction in forming the thin film magnetic head. Therefore, in order to minimize the azimuth loss, it is desirable to perform recording / reproduction while moving the magnetic recording medium in the X direction, and the X direction is usually taken in the recording track length direction.

When the optical adjustment is performed so that the optical axis C of the incident light Li is along the side surface 21S of the main magnetic pole 21, the spot center is disposed on the end surface 21T along the side surface 21S of the main magnetic pole 21. The intensity of the photoelectric field due to the incident light Li is significantly increased at the focal point on the bottom surface of the SIL 2 and causes dielectric polarization in the adjacent main pole 21. This is because the main magnetic pole 21 is made of a magnetic metal such as Co, Ni alloy, etc., but excitation vibration of free electrons due to the incident photoelectric field P occurs.
At the interface between the metal and the dielectric, free electron vibration is excited by the incident photoelectric field. When the dielectric constant of metal and dielectric is ε (ω) and εm,
ε (ω) <0
| Ε (ω) |> εm
When the condition is satisfied, surface plasmon resonance occurs, and free electron vibration propagates as a plane wave along the interface, and behaves as an evanescent wave that decays exponentially as it moves away from the surface. In magnetic metals such as Co and Ni alloys, the dielectric constant becomes an imaginary number and does not reach a resonance state. Occurs. That is, a surface plasma wave localized on the metal surface is generated, and this surface plasma wave causes dielectric polarization in the main magnetic pole 21. In particular, since the incident photoelectric field intensity is large at the focal plane, the dielectric polarization effect is large, and electric field concentration occurs at the corner on the optical axis C side of the end face 21T of the main pole 21, so that significant dielectric polarization occurs.

  When the polarization plane of the incident light, that is, the electric field vibration direction P of the incident light is taken as the X direction, the above dielectric polarization effect occurs only at the end of the main pole 21 on the optical axis C side of the incident light Li. The amplification of the photoelectric field intensity occurs at the end of the incident light Li on the optical axis C side. As a result, a light spot can be formed in the vicinity of the end of the incident light Li of the main magnetic pole 21 on the optical axis C side, and local electric field concentration at the end of the main magnetic pole 21 on the optical axis C side The formation of a light spot localized at the end of the main magnetic pole 21, that is, the spot diameter can be significantly reduced and the spot size can be miniaturized.

11A and 11B show spot profiles (photoelectric field energy distribution) when the electric field vibration direction P of the incident light Li is parallel to the traveling direction M (that is, the recording track length direction) of the magnetic recording medium and when they are orthogonal to each other. The analysis results are shown respectively. In this example, the conditions of the optical system are as follows. That is, the numerical aperture of the objective lens is 0.75, the refractive index of SIL is 1.92 with respect to the incident light wavelength, the material of SIL2 is optical glass S-LAH58 (trade name, manufactured by OHARA INC.), Incident light The wavelength is 400 nm. The effective numerical aperture of the condensing optical system 4 including the objective lens 3 and the SIL 2 is 1.44.
In this example, in the structure described with reference to FIG. 5, the depth length ld of the main magnetic pole 21 and the widths wm and wy of the main magnetic pole 21 and the yoke 25 in the direction orthogonal to the relative running direction with respect to the magnetic recording medium. Are the cases where ld = 3 μm, wm = 0.15 μm, and wy = 4 μm, respectively. The material of the main magnetic pole 21 was Co.
The analysis was performed by the FDTD method (Finite Difference Time Domain). 11A and 11B show the energy distribution on the surface of the magnetic recording medium, and the light intensity is shown by gradation from white to black. The distance between the end surface of the SIL and the surface of the magnetic recording medium was 20 nm.

As shown in FIG. 11A, when the electric field vibration direction P is taken in the X direction, that is, the relative traveling direction M with respect to the magnetic recording medium, as described above, a single photoelectric field energy strong on the incident end side of the main magnetic pole 21 is used. It can be seen that the peak (white part) of is generated. It can be seen that the position of the light spot on the magnetic recording medium substantially coincides with the inflow end of the main magnetic pole 21 and that the portion immediately below the main magnetic pole 21 is also irradiated.
On the other hand, as shown in FIG. 11B, when the electric field vibration direction P is taken in the Y direction, that is, the direction perpendicular to the traveling direction M relative to the magnetic recording medium, the Y direction, that is, in this case, recording on the magnetic recording medium is performed. Two peaks of photoelectric field energy occur in the track width direction of the track. That is, since the light spot is separated, the energy is dispersed, and a large photoelectric field energy cannot be obtained at the inflow end of the main magnetic pole 21 to which the recording magnetic field is applied.

Although not shown in FIG. 11, when the incident light is circularly polarized light, an average characteristic between both arrangements of the linearly polarized light shown in FIGS. 11A and 11B is obtained, and the electric field vibration direction shown in FIG. Compared to the X direction, the effect of miniaturizing the spot size is small.
Even when the optical axis C is not close to the central portion of the side surface on the inflow end side of the main magnetic pole 21 but close to the end portion in the Y direction, the photoelectric field energy distribution differs from FIG. The peak cannot be obtained. Also, since the recording magnetic field distribution is maximized near the center of the main magnetic pole and is reduced at the end in the Y direction, it is desirable that the optical axis be near the center of the main magnetic pole in terms of positioning with the recording magnetic field. Therefore, it is desirable that the optical axis C be arranged at the approximate center in the Y direction of the side surface 21S of the main magnetic pole 21 as much as possible.

FIG. 12 shows the photoelectric field energy distribution and the magnetic field distribution when the X direction is the electric field vibration direction P. In FIG. 12, solid lines a and b indicate the photoelectric field energy at the surface of the magnetic recording medium and at the bottom of the SIL, respectively. A broken line c indicates a recording magnetic field by the main magnetic pole. The X axis is indicated by hatching with the optical axis, that is, the inflow end of the main magnetic pole as the origin, and the region where the main magnetic pole exists as X21.
As is clear from FIG. 12, the bottom surface of the SIL also has a shielding effect of the main pole itself and the light energy is small, but on the surface of the magnetic recording medium, the photoelectric field energy increases due to the dielectric polarization of the main pole. I understand that. Furthermore, a sharp peak occurs at the inflow end of the main pole, and its half-value width is about 50 nm. Since the spot half-value width by the condensing optical diameter using the SIL having the same shape without the main magnetic pole is 140 nm, it is understood that the spot diameter is reduced and miniaturized.
At the same time, it can be seen that the recording magnetic field is sufficiently high at about 5000 [Oe] at the inflow end. Since the magnetic layer of the magnetic recording medium is heated to near its Curie temperature by the light assist effect, it is expected that sufficient magnetic recording can be performed with this recording magnetic field. Therefore, it can be confirmed that the optically assisted magnetic recording is surely performed.

For reference, FIGS. 13A and 13B show the photoelectric field energy distribution on the bottom surface of the SIL, that is, the front end surface of the main magnetic pole, and the photoelectric field energy distribution on the surface of the magnetic recording medium. In FIG. 13A, Z = 0 nm, that is, the front end surface of the main pole, and in FIG. 13B, Z = −20 nm, that is, the surface of the magnetic recording medium. Both examples show a case where the electric field vibration direction P of incident light is parallel to the traveling direction M of the magnetic recording medium.
As is apparent from FIG. 13A, the photoelectric field energy is almost zero at the front end surface of the main pole 21, and as shown in FIG. 13B, it can be seen that evanescent light is generated only on the surface of the magnetic recording medium. .

As described above, according to the present invention, the following effects can be obtained.
1. According to the present invention, the light spot and the main magnetic pole of the thin-film magnetic head can be arranged close to each other with an interval of less than 100 nm and on the order of 10 nm, that is, the peak position of the light spot is arranged close to the end portion on the inflow side of the main magnetic pole. be able to.
2. The light spot diameter can be reduced, particularly a spot having a diameter of 50 nm or less can be formed at the end of the main pole of the thin film magnetic head.
3. Due to the effects 1 and 2, a high recording magnetic field gradient due to the light assist effect can be generated. As a result, the recording bit length can be reduced and the recording density can be improved.
4). It becomes possible to record on a magnetic recording medium having higher magnetic anisotropy energy (Ku). As a result, it is possible to increase the recording density and suppress the thermomagnetic relaxation and extend the recording data life.

As described above, according to the present invention, an optically assisted magnetic head device and an optically assisted magnetic recording device that achieve a high recording density of 1 Tbit / inch ² or higher, which has been difficult to realize with conventional magnetic recording and reproducing devices. Can be provided. That is, by arranging a light spot having a spot diameter of the order of 10 nm close to the end of the recording head magnetic pole in the order of 10 nm, a sufficient recording magnetic field and a light spot intensity can be achieved at the same time. By using, the size of the recording domain can be reduced to 10 nm or less, and the recording density can be improved.

  The present invention is not limited to the configuration described in the above-described embodiment, and various modifications and changes can be made without departing from the configuration of the present invention. For example, in the optically assisted magnetic head device and the optically assisted magnetic recording device of the present invention, a margin can be provided in the arrangement of the optical axis and the main magnetic pole of the thin film magnetic head within the range of variations caused by optical adjustment. Is possible. For example, even if the optical axis deviates from the center of the side surface on the inflow end side of the main pole within the range of the margin of optical adjustment, the peak position of the light spot is on the order of 10 nm at the end of the main pole as in the case of the center arrangement It can be made close by.

On the other hand, when the optical axis is arranged at the Y direction end of the inflow side surface of the main magnetic pole, a good photoelectric field energy distribution cannot be obtained, and the same effect as the present invention cannot be obtained. The incident photoelectric field distribution can be considered to have a Gaussian distribution near the focal plane, but in order to generate a unimodal peak at the end of the main pole, the vicinity of the top of the Gaussian distribution where the incident photoelectric field can be regarded as almost constant is mainly used. Must match the pole tip. This is considered to be a range of about 1/3 to 1/4 of the spot diameter by SIL.
That is, in the present invention, it can be said that the deviation in the arrangement of the main magnetic pole and the optical axis may be in a range where the peak is single in the photoelectric field energy distribution.

  In addition, in the optically assisted magnetic recording method of the present invention, it is also possible to use other near-field light irradiation means such as SIM (Solid Immersion Mirror) without using SIL in the condensing optical system.

1 is a cross-sectional configuration diagram of an optically assisted magnetic head device according to an embodiment of the present invention. 1 is a perspective configuration diagram of a main part of an optically assisted magnetic head device according to an embodiment of the present invention. 1 is a perspective configuration diagram of an optically assisted magnetic head device according to an embodiment of the present invention. FIG. 1 is a perspective configuration diagram in which a part of an optically assisted magnetic head device according to an embodiment of the present invention is cut away. FIG. 1 is a cross-sectional configuration diagram of a main part of an optically assisted magnetic head device according to an embodiment of the present invention. FIGS. 2A and 2B are a cross-sectional configuration diagram and a plan configuration diagram of the main part of the optically assisted magnetic head device according to the embodiment of the present invention. 1 is a schematic configuration diagram of an optically assisted magnetic recording apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of an optically assisted magnetic recording apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of an optically assisted magnetic recording apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the relationship between the main pole and incident photoelectric field of the optically assisted magnetic head apparatus which concerns on embodiment of this invention. A and B are diagrams showing photoelectric field energy distributions according to an embodiment of the present invention and a comparative example, respectively. It is a figure which shows the photoelectric field intensity distribution and magnetic field intensity distribution with respect to the position of the recording track direction on the magnetic recording medium surface in embodiment of this invention. A and B are diagrams showing photoelectric field energy distributions on the end surface of the SIL and the surface of the magnetic recording medium in the optically assisted magnetic head device according to the embodiment of the present invention, respectively.

Explanation of symbols

  1. 1. magnetic recording medium; SIL, 2S. Spherical part, 2P. 2. optical material part; Objective lens, 4. 4. Condensing optical system Thin film magnetic head, 6a. First optical block, 6b. 8. second optical block; Spacer, 10. 11. optically assisted magnetic head device; Terminal lead-out section, 13. Electrodes, 18. Suspension, 19. Slider, 21. Main pole, 23. Coil, 25. York, 30. Light source unit, 100. Optically assisted magnetic recording device

Claims (8)

A condensing optical system and a thin film magnetic head;
The condensing optical system includes a hemispherical or super hemispherical solid immersion lens,
The main magnetic pole of the thin-film magnetic head has a side surface on the inflow end side relative to the magnetic recording medium along the optical axis of the condensing optical system, and the optical axis is disposed at the center of the side surface.
The light condensed on the central portion of the side surface of the main magnetic pole by the condensing optical system is linearly polarized light, and the electric field vibration direction is arranged along the relative traveling direction with the magnetic recording medium. An optically assisted magnetic head device. The solid immersion lens is composed of a spherical portion constituting a spherical lens, and an optical material portion disposed on the surface facing the magnetic recording medium,
2. The optically assisted magnetic head device according to claim 1, wherein the thin film magnetic head is formed on the optical material portion. The optical material portion includes a first optical block on which the thin film magnetic head is formed, and a second optical block.
3. The optically assisted magnetic head device according to claim 2, wherein the first and second optical blocks are joined with the surface on which the thin film magnetic head is formed facing inward. A light source unit;
A magnetic recording medium placement section;
A thin film magnetic head;
A recording signal control unit;
A condensing optical system for guiding the light from the light source unit to the thin film magnetic head,
The condensing optical system includes a hemispherical or super hemispherical solid immersion lens,
The main magnetic pole of the thin-film magnetic head has a side surface on the inflow end side relative to the magnetic recording medium along the optical axis of the condensing optical system, and the optical axis is disposed at the center of the side surface.
The light condensed on the central portion of the side surface of the main magnetic pole by the condensing optical system is linearly polarized light, and the electric field vibration direction is arranged along the relative traveling direction with the magnetic recording medium. An optically assisted magnetic recording apparatus.   5. The optically assisted magnetic recording apparatus according to claim 4, wherein the thin film magnetic head is mounted on a flying slider. The thin film magnetic recording head is mounted on an actuator for positioning in a normal direction with respect to the surface of the magnetic recording medium,
5. The optically assisted magnetic recording apparatus according to claim 4, wherein a distance between the thin film magnetic head and the magnetic recording medium is controlled using return light from the near field from the magnetic recording medium. A thin film magnetic head is placed at the focusing spot position of the focusing optical system,
The main magnetic pole of the thin film magnetic head has a side surface on the inflow end side relative to the magnetic recording medium along the optical axis of the condensing optical system, and the optical axis is disposed at the center of the side surface. ,
By the condensing optical system, linearly polarized light whose electric field vibration direction is along the traveling direction relative to the magnetic field is incident on the main magnetic pole, and near-field light is emitted from the tip position along the optical axis of the main magnetic pole. An optically assisted magnetic recording method which is generated and recorded on the magnetic recording medium. 8. The optically assisted magnetic recording method according to claim 7, wherein a hemispherical or super hemispherical solid immersion lens is used for the condensing optical system.