JP2009163834A - Electromagnetic field generation element, recording head, and information recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate near-field light in a small area in an electromagnetic field generation element. <P>SOLUTION: The electromagnetic field generation element 1 includes a substrate 10, a conductive layer 11 in which a slit 14 is formed, and two kinds of protective layers 12 having different refractive indices. The conductive layer 11 includes a narrow part 15 narrowed by the slit 14. By irradiating the narrow part 15 with a laser beam, the near-field light is generated in the vicinity of the slit 14 at the narrow part 15. By means of the refractive indices of the materials forming the protective layers 12, the first protective layer 12a propagates the near-field light, and the second protective layer 12b does not propagate the near-field light. Thus, the near-field light is generated in a small area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electromagnetic field generating element, a recording head, and an information recording / reproducing apparatus including the same.

Currently, various research and development aimed at increasing the capacity of optical recording media, magnetic recording media, and these recording / reproducing apparatuses are underway. Among these, the optically assisted magnetic recording method is attracting attention as the next generation high density magnetic recording. This technique performs magnetic recording on a magnetic recording medium having a high coercive force that is resistant to thermal fluctuations, and can achieve a magnetic recording density exceeding 100 Gb / inch ² . Specifically, light is condensed on a magnetic recording medium having a magnetic compensation point temperature at room temperature, and the temperature of the magnetic recording medium is locally increased. Since the coercive force decreases at the portion where the temperature has risen, magnetic recording by a normal magnetic head becomes possible.

In recent years, a method using near-field light has been proposed to perform higher density recording. As disclosed in Patent Document 1, near-field light is minute light generated in a region near the opening by irradiating the minute opening with light. In the case of using near-field light, an information recording medium can be heated in a region smaller than a normal light irradiation region, so that higher density recording is expected.
JP 2001-291265 A (publication date October 19, 2001)

  The generation of near-field light depends on the polarization direction of the light applied to the minute opening, and the generation region depends on the shape of the minute opening. If this generation area can be further narrowed, a finer mark can be recorded. However, in the conventional optically assisted magnetic recording system, there is a limit to miniaturization of the near-field light generation region.

  In addition, if the irradiation power of light to the minute opening is increased, the near-field light can be miniaturized. However, when the irradiation power is increased, the amount of heat transferred to the information recording medium increases. As a result, heat conduction in the information recording medium increases, and the temperature rising area in the information recording medium increases.

  Therefore, the present invention has been made in view of the above-mentioned problems, and the object thereof is miniaturized by miniaturizing the generation region of near-field light without increasing the light irradiation power to the minute aperture. Another object of the present invention is to provide an electromagnetic field generating element capable of performing optically assisted magnetic recording using near-field light, a recording head including the same, and an information recording / reproducing apparatus.

  In order to solve the above problems, an electromagnetic field generating element according to the present invention is formed on a substrate, a slit made of a dielectric layer, and formed on the substrate, and is narrowed by the slit. A conductive layer having a constricted portion and a protective layer formed on the conductor layer and the slit, and the near-field light is generated from the constricted portion by irradiating light from a light source to the constricted portion. In the electromagnetic field generating element, the protective layer includes a plurality of protective layers having different refractive indexes, and a first protective layer of the plurality of protective layers and a second different from the first protective layer. The boundary with the protective layer is on the slit.

  According to the above configuration, when the electromagnetic field generating element is irradiated with light from the light source, near-field light is generated in the narrowed portion of the conductor layer. It is assumed that the light from the light source is irradiated from the opposite side of the conductor layer across the substrate. Then, this near-field light propagates to the protective layer side.

  Further, the first protective layer and the second protective layer have different refractive indexes. Furthermore, the boundary between the first protective layer and the second protective layer is on the slit. Near-field light is generated in the vicinity of the slit in the constricted portion of the conductor layer, so that the propagation of the near-field light in the protective layer differs between the first protective layer and the second protective layer. That is, it is divided into a region where propagation is maintained and a region where propagation is prevented. Thereby, only a part of the near-field light generated from the constriction part can be propagated, and other propagation can be prevented. As a result, the electromagnetic field generating element in the present invention can further reduce the near-field light generation region as compared with the conventional element.

  In the electromagnetic field generating element according to the present invention, the real part of the refractive index of the first protective layer is preferably larger than the real part of the refractive index of the second protective layer.

  With the above configuration, the first protective layer can more reliably propagate near-field light, and the second protective layer can more reliably prevent the propagation of near-field light. Therefore, the electromagnetic field generating element according to the present invention can efficiently miniaturize the near-field light generation region.

  In the electromagnetic field generating element according to the present invention, the real part of the refractive index of the first protective layer is larger than the real part of the refractive index of the slit, and the real part of the refractive index of the second protective layer is It is preferable that it is smaller than the real part of the refractive index of the slit.

  With the above configuration, the magnitude relationship between the refractive index of the first protective layer and the second protective layer and the refractive index of the slit is further set. Accordingly, near-field light can be more reliably propagated in the first protective layer than in the case where the above configuration is not used, and near-field light is more reliably propagated in the second protective layer. Can be prevented. Therefore, the electromagnetic field generating element in the present invention can further miniaturize the near-field light generating region efficiently.

  In the electromagnetic field generating element according to the present invention, it is preferable that the hardness of the protective layer is larger than the hardness of the slit and the conductor layer.

  When the electromagnetic field generating element according to the present invention is used for a flying head in an information recording / reproducing apparatus, the flying head keeps a distance from the information recording medium constant by a flying pressure with the information recording medium. Since the flying height is as small as about 10 nm, the slit and the conductor layer may be damaged by contact with the information recording medium. With the above configuration, the slit and the conductor layer can be prevented from being damaged by the protective layer.

  In the electromagnetic field generating element according to the present invention, the slit is made of quartz, the first protective layer is made of titanium oxide, silicon nitride, or aluminum oxide, and the second protective layer is nitrided. It is preferable to consist of titanium.

  With the above configuration, it is possible to provide an electromagnetic field generating element that suitably realizes near-field light miniaturization.

  In the electromagnetic field generating element according to the present invention, a semiconductor laser element is preferably provided on the substrate.

  According to the said structure, since a light source and an electromagnetic field generating element can be integrated, the distance between them can be made constant. Thereby, the electromagnetic field generating element can be accurately irradiated with light from the light source. Further, when the electromagnetic field generating element according to the present invention is used for a recording head, a more compact recording head can be provided.

  Further, by providing the electromagnetic field generating element according to the present invention and the suspension, it can function as a recording head. Further, the recording head, the optically assisted magnetic recording medium, and the reproducing element for reproducing the information recorded on the optically assisted magnetic recording medium can be suitably used as an information recording / reproducing apparatus.

  The reproducing element may be provided on the substrate. Since an electromagnetic field generating element and a reproducing element are provided on one substrate, a compact information recording / reproducing apparatus can be provided.

  An electromagnetic field generating element according to the present invention includes a conductor layer in which a slit is formed, and the conductor layer and a protective layer formed on the slit, and the protective layer has at least two types of protective layers having different refractive indexes. And having the boundary of the protective layer on the slit, it is possible to perform optically assisted magnetic recording by miniaturized near-field light.

Embodiment 1
The electromagnetic field generating element 1 according to the first embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, the case where the electromagnetic field generating element 1 is used for the recording head 2 for recording information on the information recording medium will be described, but the present invention is not limited to this.

(Overall configuration of recording head 2)
First, the recording head 2 and the electromagnetic field generating element 1 according to the present embodiment will be described below with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view of the recording head 2 as viewed from the side. FIG. 4 is a plan view of the recording head 2 as viewed from the front.

  As shown in FIG. 3, the recording head 2 has a configuration in which a suspension 13 is attached to the electromagnetic field generating element 1. The electromagnetic field generating element 1 includes a substrate 10, a conductor layer 11, and a protective layer 12, and the protective layer 12 is formed to face the substrate 10 with the conductor layer 11 interposed therebetween.

  The substrate 10 can be used as a slider by producing an ABS (Air Bearing Surface) surface. Or the structure which provides the board | substrate 10 in a slider may be sufficient. Thereby, the recording head 2 can be a floating recording head.

  In the flying type recording head, the information recording medium is disposed below the surface of the conductor layer 11, and the recording head 2 floats on the information recording medium with a flying height of about 10 nm. In FIG. 3, when the information recording medium moves from the left side to the right side, air flows from the direction of the arrow toward the recording head 2. Therefore, the right side of the substrate 10 is the air inflow end and the left side is the outflow end. FIG. 4 is a view of the recording head 2 as viewed from the air outflow end side.

(Configuration of electromagnetic field generating element 1)
The configuration of the electromagnetic field generating element 1 will be described in detail below with reference to FIG. FIG. 1 is a plan view showing the conductor layer 11 when the electromagnetic field generating element 1 is viewed from the protective layer 12 side. In FIG. 1, the protective layer 12 on the front surface is transmitted, and the conductor layer 11 on the back surface is indicated by hatched portions. Further, in the plane of the electromagnetic field generating element 1, the air inflow direction is defined as the Y direction, and the perpendicular direction thereof is defined as the X direction.

  As shown in FIG. 1, the electromagnetic field generating element 1 includes a substrate 10, a conductor layer 11, and a protective layer 12, and a slit 14 is formed in the conductor layer 11. Moreover, the conductor layer 11 has a narrowed portion 15 whose width in the Y direction is partially narrowed by the slit 14.

  In FIG. 1, when the width of the conductor layer 11 in the Y direction is 1500 nm, the size of the slit 14 is, for example, a width of 250 nm in the X direction and a width of 1000 nm in the Y direction, and the width in the Y direction of the narrowed portion 15 is 500 nm. It becomes.

Further, the substrate 10 is formed from quartz (SiO ₂ ) having translucency. The conductor layer 11 is made of gold (Au) as a material and is formed on the substrate 10. Therefore, the slit 14 formed in the conductor layer 11 is made of SiO ₂ that forms the substrate 10. The protective layer 12 includes a first protective layer 12a and a second protective layer 12b having different refractive indexes.

In order to form the conductor layer 11 and the protective layer 12 on the substrate 10, for example, a process combining a lithography technique and a lift-off method may be used, and no special process is required. The substrate 10 is not limited to the SiO ₂ substrate, and the conductor layer 11 and the protective layer 12 may be formed after forming the SiO ₂ film on another substrate. Thereby, the inside of the slit 14 can be made of SiO ₂ .

(Near-field light generation method)
Next, a method for generating near-field light will be described below with reference to FIG.

  In FIG. 1, when a laser beam having a wavelength of 635 nm is irradiated to the boundary with the narrowed portion 15 slit 14 from the back side of the paper, the free electrons at the edge portion in the conductor layer 11 are shaken by the electric field of light. As this vibration is transmitted to the electrons of the conductor layer 11, surface plasmons are generated.

  More specifically, the near-field light described in the present invention is local plasmon, surface plasmon, evanescent light, or the like. Therefore, when the constriction 15 has a size smaller than the wavelength of the laser light, electric field concentration occurs in the constriction 15 and near-field light is generated near the surface pole of the constriction 15.

  This near-field light travels in a direction perpendicular to the edge of the conductor layer 11 and propagates to the protective layer 12 side. Further, when the polarization direction of incident light is perpendicular to the edge of the conductor layer 11, surface plasmon is most likely to occur. Therefore, when the polarization direction of the laser light is set to the Y direction, near-field light is concentrated and generated in the near-field light generating unit 16 shown in FIG. Further, when the polarization direction of the laser light is set to the X direction, near-field light is concentrated and generated in the near-field light generating unit 16 shown in FIG. FIG. 2 is a plan view for explaining the near-field light generation region when the laser beam whose deflection direction is the X direction is irradiated. The behavior of near-field light propagated to the protective layer 12 side will be described later in the following examples.

(Miniaturization of near-field light)
As shown in FIG. 1, the protective layer 12 includes a first protective layer 12a and a second protective layer 12b having different refractive indexes. The boundary 17 between the first protective layer 12a and the second protective layer 12b is disposed so as to pass through the center of the slit 14 in the Y direction. However, the boundary 17 is not limited to this arrangement as long as it is on the slit 14.

  In addition, although selection of the material which forms the protective layer 12, and the miniaturization of near-field light by it will be described in detail later in the section of the examples, the first protective layer 12a and the second protective layer 12b having different refractive indexes are described. However, there is a difference in the propagation of near-field light. Furthermore, since the boundary 17 of the protective layer 12 is on the slit 14, the near-field light generation region in the vicinity of the slit 14 is divided into a region where propagation is maintained and a region where propagation is prevented. Accordingly, the near-field light generation region is miniaturized.

  In this embodiment, two layers of the first protective layer 12a and the second protective layer 12b are used as the protective layer 12. However, the present invention is not limited to this, and three or more layers may be used. Also in this case, the boundary 17 between the protective layers 12 is disposed on the slit 14, so that the near-field light generation region can be further miniaturized.

(Generation method of magnetic field)
Next, a method for generating a magnetic field will be described below with reference to FIG.

  When a current is applied to the conductor layer 11 from an electrode (not shown), a magnetic field is generated in the slit 14 according to the right-hand rule. For example, in the conductor layer 11 of FIG. 1, when a current is applied from the left side to the right side of the paper, a magnetic field is generated in the slit 14 in the direction from the front of the paper to the back. On the other hand, when a current is applied from the right side to the left side of the paper, a magnetic field is generated in the slit 14 in the direction from the back of the paper to the front.

  Further, since the narrowed portion 15 is narrower in the Y direction than the surrounding conductor layer 11, the current density is increased even when the same current is applied. Therefore, a magnetic field concentrates in the slit 14 and a large magnetic field is generated. Therefore, near-field light and a very large magnetic field can be generated in the vicinity of the constricted portion 15. These enable high-density magnetic recording on the information recording medium.

[Embodiment 2]
The electromagnetic field generating element 1 ′ according to the second embodiment of the present invention will be described below with reference to FIG. FIG. 5 is a plan view showing the conductor layer 11 when the electromagnetic field generating element 1 ′ is viewed from the protective layer 12 side. 5, except for the configuration of the protective layer 12, the configuration is the same as in FIGS. 1 and 2, and the same reference numerals are given to the same components.

  As shown in FIG. 5, the electromagnetic field generating element 1 ′ has a configuration including three protective layers 12. Specifically, the first protective layer 12b is arranged on both sides of the second protective layer 12a. In addition, two boundaries 17 between the first protective layer 12a and the second protective layer 12b are disposed on the slit 14 in the Y direction.

  With the above configuration, the position of the first protective layer 12 a is arranged near the center of the near-field light generating unit 16. In the present embodiment, the material for forming the protective layer 12 is selected so that the first protective layer 12a is a region where propagation is maintained and the second protective layer 12b is a region where propagation is prevented. Thereby, the near-field light generation region is further miniaturized in the vicinity of the center of the near-field light generator 16. The material of the protective layer 12 to be selected will be described later in detail in the example section.

  Further, the center of the near-field light generator 16 is in a region where the magnetic field in the slit 14 is most concentrated. Therefore, near-center light near the center of the near-field light generating unit 16 can be generated with a miniaturized near-field light and the largest magnetic field.

[Embodiment 3]
The recording heads 30 and 40 according to the third embodiment of the present invention include a reproducing element 20. The recording heads 30 and 40 will be described with reference to FIGS. FIG. 6 is a cross-sectional view schematically showing the recording head 30, and FIG. 7 is a cross-sectional view schematically showing the recording head 40. The recording heads 30 and 40 have the same basic configuration as that of the recording head 2, and the same reference numerals are assigned to the same components.

  As shown in FIG. 6, the recording head 30 includes a conductor layer 11, a substrate 10, a protective layer 12, a reproducing element 20, a light source 21, and a suspension 13. Further, the substrate 10 is mounted with a light source 21 and a reproducing element 20 for irradiating light to the constricted portion 15 formed in the conductor layer 11.

  Further, as shown in FIG. 7, the recording head 40 does not include the light source 22. However, by installing the light source 22 outside the recording head 40, the storage head 40 can be irradiated with light.

  As the light sources 21 and 22, a semiconductor laser can be used. As the reproducing element 20, a GMR (Giant Magneto Resistive), a TMR (Tunneling Magneto Resistive), or the like may be used.

  According to the above configuration, by using the recording heads 30 and 40, optically assisted magnetic recording and reproduction can be performed. In the recording head 30, since the electromagnetic field generating element 1 and the light source 21 are integrated, the distance between the laser element of the light source 21 and the narrowed portion 15 in the conductor layer 11 can be made constant. As a result, the constricted portion 15 can be accurately irradiated with laser light. The recording head 40 can be used in an information recording / reproducing apparatus as a more compact recording head 40.

[Embodiment 4]
(Overall configuration of information recording / reproducing apparatus 200)
An information recording / reproducing apparatus 200 according to a fourth embodiment of the present invention will be described below with reference to FIGS. FIG. 8 is a plan view schematically showing the information recording / reproducing apparatus 200 according to the present embodiment. FIG. 9 is a block diagram illustrating a configuration of a control unit that controls driving of the information recording / reproducing apparatus 200 according to the present embodiment.

  As shown in FIG. 8, the information recording / reproducing apparatus 200 includes a recording head 100, a suspension 201, an arm 202, an actuator 203, a spindle 204, and an information recording medium 205. The recording head 100 corresponds to the recording head 2 described in the first embodiment or the recording heads 30 and 40 described in the second embodiment.

  The recording head 100 is supported by a suspension 201, and the suspension 201 is supported by an arm 202. Further, the arm 202 is supported by the actuator 203.

  The information recording medium 205 is attached to the spindle 204 and can be rotated at a predetermined rotation speed by the spindle 204. The actuator 203 controls the position of the recording head 100 and slides on the information recording medium 22. The recording head 100 moved to a predetermined position records or reproduces information on the information recording medium 22.

  The information recording medium 205 is not limited to the optically assisted magnetic recording medium, and may be a magneto-optical recording medium that is recorded by light and magnetism such as MO and MD.

(Control method of information recording / reproducing apparatus 200)
As shown in FIG. 9, the information recording / reproducing apparatus 200 has a control unit 300 including a spindle driving circuit 302, a recording head driving circuit 304, a position control circuit 303, and a control circuit 301 for controlling them. is doing.

  The spindle drive circuit 302 controls the rotation drive of the information recording medium 205. The position control circuit 303 scans the recording head 100 to a desired position by controlling the actuator 203. The recording head drive circuit 304 controls the intensity or irradiation time of near-field light generated from the electromagnetic field generating element 1 provided on the recording head 100. The control circuit 301 comprehensively controls these circuits.

  Although not shown in FIG. 9, the recording head drive circuit 304 includes a current control mechanism (including a drive circuit) that controls generation of a current applied to the electromagnetic field generating element 1 and laser light irradiation from a light source. A light control mechanism for controlling As these current control mechanism and light control mechanism, known configurations can be adopted.

(Recording operation of information recording / reproducing apparatus 200)
The recording operation of the information recording / reproducing apparatus 200 will be described below with reference to FIG. 1 and FIG. First, the spindle drive circuit 302 rotates the spindle 204 at an appropriate rotational speed. As a result, the information recording medium 22 rotates at a predetermined rotational speed. Next, the actuator 203 is driven by the position control circuit 303 to move the recording head 100 to a desired position on the information recording medium 22. Next, the recording head drive circuit 304 applies a current to the electromagnetic field generating element 1 to generate a magnetic field, and irradiates the narrowed portion 15 with laser light. At this time, the amount and frequency of the applied current, the intensity of the laser beam, and the irradiation time are appropriately controlled.

  A magnetic field generated in the electromagnetic field generating element 1 is applied to the information recording medium 205. At the same time, near-field light is locally generated in the electromagnetic field generating element 1 irradiated with the laser light, and this near-field light is propagated to the information recording medium 205. Therefore, information is recorded on the information recording medium 205.

  With the configuration described above, the information recording / reproducing apparatus 200 can make a minute mark on the information recording medium 205 by using the miniaturized near-field light, and can perform high-density recording.

  The control circuit 301 gives an instruction to each of the above circuits to control the spindle 204, the actuator 203, and the recording head 100 so that desired recording can be performed at a desired location.

(Floating of the recording head 100)
When the floating recording head 100 is used as in the present embodiment, the recording head 100 can keep the distance from the information recording medium 205 constant by the flying pressure between the recording head 100 and the information recording medium 205. . The flying height at this time is appropriately adjusted according to the rotational speed of the information recording medium 205, the design of the suspension 201, and the like. In order to propagate the near-field light to the information recording medium 205 satisfactorily, the flying height is preferably small. However, if the flying height is too small, the recording head 100 and the information recording medium 205 come into contact with each other. As a result, the risk of damage to the recording head 100 increases.

  However, in the recording head 100, the protective layer 12 provided therein can prevent the conductor layer 11 from being damaged due to the collision with the information recording medium 205. Therefore, it is possible to provide a recording head 100 that can propagate near-field light to a smaller area of the information recording medium 205 and has good recording and reproducing characteristics without damaging the conductor layer 11.

  The present invention is not limited to the above-described embodiments. Those skilled in the art can make various modifications to the present invention within the scope of the claims. That is, a new embodiment can be obtained by combining appropriately changed technical means within the scope of the claims.

  In Examples 1 to 4, the recording head 2 according to this embodiment is irradiated with laser light whose polarization direction is the X or Y direction, and the propagation of near-field light that varies depending on the refractive index of the protective layer 12 is verified. went. In Example 5, the hardness of the protective layer 12 required when the recording head 2 was used in the information recording / reproducing apparatus 200 was verified.

  In the present embodiment, the inside of the slit 14 is represented as a dielectric layer 14.

[Example 1]
In the first embodiment, as shown in FIG. 1, the recording head 2 is irradiated with laser light whose polarization direction is the Y direction, and the intensity of the generated near-field light is calculated using the FDTD method (finite-difference time-domain method). ).

  The simulation conditions were a laser beam wavelength of 635 nm and a spot diameter of 1 μm. The laser beam was applied to the boundary between the narrowed portion 15 and the slit 14 in the recording head 2. Therefore, near-field light is generated in the vicinity of the near-field light generator 16 as shown in FIG. Therefore, the near-field light intensity was simulated in the vicinity of the near-field light generating unit 16 and near the protective layer 12 by 10 nm.

In the recording head 2, since the substrate 10 is formed of a quartz (SiO ₂ ) substrate, the inside of the slit 14 (dielectric layer 14) is SiO ₂ . The width of the slit 14 in the X direction was 250 nm. The conductor layer 11 was formed from gold (Au, film thickness 400 nm).

Further, for the two types of protective layers 12 having different refractive indexes, the first protective layer 12a was formed from titanium oxide (TiO ₂ , film thickness 10 nm), and the second protective layer 12b was formed from titanium nitride (TiN, film thickness 10 nm). The refractive index of titanium oxide is 2.52, and the refractive index of titanium nitride is 1.3-2.3i.

As a comparative example to this, a simulation was performed in the case where both the first protective layer 12a and the second protective layer 12b were titanium oxide (TiO ₂ ).

(Result of Example 1)
FIG. 10 shows the simulation results of the intensity of near-field light in Example 1 and the comparative example. FIG. 10 is a diagram showing a simulation result of the intensity of near-field light.

  In FIG. 10, the horizontal axis indicates the distance in the X direction of the slit 14, the vertical axis indicates the intensity of near-field light, the result of this example is indicated by a straight line, and the result of the comparative example is indicated by a dotted line. In the X direction of FIG. 10, 0 indicates the boundary 17 between the first protective layer 12a and the second protective layer 12b, the positive side indicates the region of the first protective layer 12a, and the negative side indicates the region of the second protective layer 12b. .

  As shown in FIG. 10, compared with the comparative example in Example 1, it was found that the near-field light intensity was reduced by about 10%, but the near-field light generation region was miniaturized. For example, when comparing the width of the slit 14 in which near-field light having an intensity of about 4 is generated, it is 130 nm in the comparative example and 90 nm in the first embodiment. Therefore, it can be seen that the near-field light generation region is miniaturized by about 30%. This simulation result shows that the irradiation area can be reduced by about 30% when recording on the information recording medium by irradiating near-field light having an intensity of 4.

  For the above reason, it is shown that near-field light propagates in the first protective layer 12a, but does not propagate in the second protective layer 12b. In the vicinity of the boundary 17, near-field light having a weak intensity is also generated in the region of the second protective layer 12b. This is considered to be caused by the near-field light propagated to the first protective layer 12a. It is done.

  Further, the intensity (a) of the near-field light generated most strongly in the first protective layer 12a was compared with the intensity (b) of the near-field light generated from the second protective layer 12b at the symmetrical position (b / a). The strength (a) is 5.91 and the strength (b) is 2.41. Therefore, in the second protective layer 12b, it was found that propagation of near-field light was prevented by about 60% compared to the first protective layer 12a. This simulation result indicates that the first protective layer 12a propagates near-field light and the second protective layer 12b prevents propagation of near-field light. As a result, it was found that the propagation region of the near-field light in the recording head 2 is miniaturized.

  Further, a magnetic field can be generated in the dielectric layer 14 by applying a current to the conductor layer 11. This magnetic field and the miniaturized near-field light enable minute marks on the information recording medium, and high-density recording can be performed.

  Even in the comparative example, if the power of the laser beam is increased, it can be narrowed down to the same generation region. However, when the power is increased, the amount of heat transferred to the information recording medium increases. As a result, the heat conduction in the information recording medium is increased, so that the temperature rising region in the information recording medium is increased.

  On the other hand, in this embodiment, the temperature of the information recording medium can be increased by the required strength, so that the temperature increase region can be miniaturized. Furthermore, since no extra heat is applied, the information recording medium is not overheated. Although the maximum intensity decreases by about 10%, the amount of decrease can be covered by adjusting the power of the laser beam to be irradiated as necessary.

[Example 2]
In Example 2, the material for forming the protective layer 12 of Example 1 was simulated when various combinations of the first protective layer 12a and the second protective layer 12b were performed. The conditions other than the protective layer 12 were the same as those in Example 1.

Near-field light generated in the recording head 2 propagates through the boundary of the dielectric layer 14. Therefore, in Example 2, a combination of a material having a high refractive index and a material having a low refractive index was examined on the basis of the refractive index 1.46 of quartz (SiO ₂ ) forming the dielectric layer 14. Note that quartz or a material having a higher refractive index than quartz was used for the first protective layer 12a, and a material having a lower refractive index was used for the second protective layer 12b.

Regarding the material of the protective layer 12, the first protective layer 12a is composed of titanium oxide (TiO ₂ ), silicon nitride (SiN), aluminum oxide (Al ₂ O ₃ ), quartz (SiO ₂ ), and the second protective layer 12b. Titanium (TiN) and carbon (C) were used. The refractive indexes of aluminum oxide, silicon nitride, and carbon were 1.76, 2.20, and 2.0-1.0i, respectively.

  As a comparative example, a combination in which the first protective layer 12a and the second protective layer 12b are both titanium oxide was used.

  In the following, in the results section of Example 2, when describing the magnitude of the refractive index, it is assumed that the real part of the refractive index is compared.

(Results of Example 2)
In Example 2 and the comparative example, the intensity (a) of the strongest near-field light generated from the first protective layer 12a and the intensity (b) of the near-field light generated from the second protective layer 12b at the symmetrical position thereof. Table 1 shows the results (b / a). Table 1 is a table showing b / a in various combinations of the first protective layer 12a and the second protective layer 12b. The value of b / a is a value that indicates the miniaturization of near-field light propagated on the protective layer 12, and indicates that the smaller the value is, the smaller the value is.

From Table 1, the b / a value of the comparative example is 1, whereas the b / a value is smaller than 1 in any combination of Example 2, and therefore the near field in the second protective layer 12b. It was found that light propagation was prevented. Hereinafter, in Table 1, the combination of the first protective layer 12a and the second protective layer 12b is (12a, 12b), and this result will be described in more detail.
(Result-1 of Example 2)
First, the combination with the 1st protective layer 12a in case the 2nd protective layer 12b is C was examined. Specifically, when the refractive index of the first protective layer 12a is smaller than the refractive index of C (Al ₂ O ₃ , C or SiO ₂ , C), and larger (TiO ₂ , C or SiN, C). Compared. As a result, it was found that the value of b / a was smaller when the refractive index of the first protective layer 12a was larger than the refractive index of the second protective layer 12b. Therefore, by making the refractive index of the first protective layer 12a larger than the refractive index of the second protective layer 12b, the near-field light generation region can be miniaturized.
(Result-2 of Example 2)
Next, the first protective layer 12a is in the case of TiO _2, was examined in combination with a second protective layer 12b. As a result, it was found that the b / a value is smaller when the second protective layer 12b is TiN than when it is C, and the near-field light generation region can be miniaturized. Note that the refractive index of TiN is smaller and the refractive index of C is larger than the refractive index of SiO ₂ forming the dielectric layer 14.

Similarly to the above, in the case where the first protective layer 12a is Al ₂ O ₃ and SiN, the combination with the second protective layer 12b was examined. As a result, similarly to the above, the value of b / a was smaller when the second protective layer 12b was TiN than when it was C.

Therefore, by making the refractive index of the first protective layer 12a larger than the refractive index of the dielectric layer 14 and making the refractive index of the second protective layer 12b smaller than the refractive index of the dielectric layer 14, Generation area can be miniaturized.
(Result-3 of Example 2)
In addition, even when the near-field light generation region is miniaturized, in order to maintain the intensity of the near-field light, it is preferable that the intensity of the near-field light propagated from the first protective layer 12a is higher. Therefore, from Table 1, the strength (a) from the first protective layer 12a was compared. As a result, the strength (a) from the first protective layer 12a is easily maintained when the first protective layer 12a is made of TiO ₂ , Al ₂ O ₃ , and SiN, and decreases when it is made of SiO _2. all right. Therefore, in order to maintain the intensity of the near-field light, it is desirable that the refractive index is higher than that of SiO ₂ of the dielectric layer 14.

  From the above results, the refractive index of the first protective layer 12a is made larger than the refractive index of the dielectric layer 14, and the refractive index of the second protective layer 12b is made smaller than the refractive index of the dielectric layer 14. It was found that the generation region of near-field light can be miniaturized while maintaining the intensity of the field light.

  In addition, the protective layer in the present invention is not limited to two layers, and the generation region of near-field light can be further miniaturized by using three or more layers.

Example 3
In Example 3, the recording head 2 was irradiated with laser light whose polarization direction was the X direction, and the intensity of the generated near-field light was simulated using an FDTD method (finite-difference time-domain method). The conditions other than the polarization direction of the laser light were the same as those in Example 1. In Example 3, since the laser light whose polarization direction is the X direction is incident, the near-field light is generated in the vicinity of the two near-field light generation regions 16 as shown in FIG.

In addition, similarly to Example 1, the comparative example was simulated for the case where both the first protective layer 12a and the second protective layer 12b were titanium oxide (TiO ₂ ).

(Result of Example 3)
FIG. 11 shows a simulation result of the intensity of near-field light in Example 3 and the comparative example. FIG. 11 is a diagram illustrating a simulation result of the intensity of near-field light.

  In FIG. 11, the horizontal axis indicates the distance in the X direction of the slit 14, the vertical axis indicates the intensity of near-field light, the result of this example is indicated by a straight line, and the result of the comparative example is indicated by a dotted line. In the X direction of FIG. 11, 0 indicates the boundary 17 between the first protective layer 12a and the second protective layer 12b, the positive side indicates the region of the first protective layer 12a, and the negative side indicates the region of the second protective layer 12b. .

  From FIG. 11, in Example 3, the near-field light from the first protective layer 12a propagates in the same manner as in the comparative example, whereas the propagated light from the second protective layer 12b is only about 50% of the comparative example. You can see that it is not propagating. In the comparative example, near-field light having the same intensity propagates from the first protective layer 12a and the second protective layer 12b.

  Therefore, in the comparative example, the information recording medium is heated by the two near-field lights, so that the heating area for the information recording medium becomes large. On the other hand, in Example 3, the information recording medium is heated by one near-field light from the first protective layer 12a. That is, in Example 3, since there is one heating region, it is possible to irradiate near-field light to a finer region.

  For example, when recording is performed with the intensity of the near-field light being about 2.5, in Example 3, the recording is performed only by the near-field light from the first protective layer 12a, whereas in the comparative example, the first protection is performed. Recording is performed by near-field light from the layer 12a and the second protective layer 12b. Therefore, in Example 3, since the irradiation area of the near-field light on the medium can be miniaturized, it is possible to record more minute marks.

Example 4
In Example 4, the material for forming the protective layer 12 of Example 3 was simulated when the first protective layer 12a and the second protective layer 12b were variously combined. In addition, the material which forms the dielectric material layer 14 and the protective layer 12 was the same as the material mentioned in Example 2. Similarly to Example 2, the comparative example was simulated for the case where both the first protective layer 12a and the second protective layer 12b were titanium oxide (TiO ₂ ).

  Hereinafter, in the term of the results of Example 4, when the magnitude of the refractive index is described, it is assumed that the real part of the refractive index is compared.

(Result of Example 4)
In Example 4 and the comparative example, the strongest near-field light intensity (a) generated from the first protective layer 12a was compared with the strongest near-field light intensity (b) generated from the second protective layer 12b. (B / a) The results are shown in Table 2. Table 2 is a table | surface which shows b / a in various combinations of the 1st protective layer 12a and the 2nd protective layer 12b. The value of b / a is a value that indicates the miniaturization of near-field light propagated on the protective layer 12, and indicates that the smaller the value is, the smaller the value is.

  From Table 2, the b / a value of the comparative example is 1, whereas in any combination of Example 4, the b / a value is smaller than 1. Therefore, the second protective layer 12b has a near field. It was found that light propagation was prevented.

  Furthermore, as a result of comparison similar to the comparison in Example 2, the same result as in Example 2 was obtained. That is, the refractive index of the first protective layer 12a and the refractive index of the second protective layer 12b are reduced by making the refractive index of the first protective layer 12a smaller than the refractive index of the dielectric layer 14, while maintaining the near-field light intensity. It was found that the light generation region can be miniaturized.

  From the above, it can be seen that by using the first protective layer 12a and the second protective layer 12b having different refractive indexes, the propagation of the near-field light can be controlled and the heating region by the near-field light can be miniaturized. In addition, since a magnetic field can be generated in the slit 14 by applying a current to the conductor layer 11, more minute marks can be recorded and high density recording can be performed.

  In addition, the protective layer 12 in the present invention is not limited to two layers, and the generation region of near-field light can be further miniaturized by using three or more layers.

Example 5
In Example 5, as shown in FIG. 8, the hardness of the protective layer 12 required when the recording head 2 was used in the information recording / reproducing apparatus 200 was verified.

  The recording head 2 keeps the distance from the information recording medium 205 constant by the flying pressure with the information recording medium 205. Since the flying height is as small as about 10 nm, the recording head 2 may be damaged due to a collision with the information recording medium 205 or the like. In particular, if the conductor layer 11 is damaged, no current can be applied, and a sufficient magnetic field cannot be applied to the dielectric layer 14. For this reason, it is necessary to prevent the conductor layer 11 from being damaged.

  Therefore, the recording head 2 needs a protective layer 12 having a hardness higher than that of the conductor layer 11. Therefore, the hardness of the material forming the protective layer 12 used in Examples 1 to 4 and the hardness of Au forming the conductor layer 11 were compared with reference to Table 3. Table 3 shows the material forming the protective layer 12 and the hardness of Au forming the conductor layer 11.

  From Table 3, the material which forms the protective layer 12 used in Examples 1 to 4 shows a higher hardness than Au which is the conductor layer 11. Therefore, even when the recording head 2 and the information recording medium collide, the conductor layer 11 can be protected. Further, when TiN, Al 2 O 3, and SiN are used for the protective layer 12, since these have higher hardness than SiO 2 that is the dielectric layer 14, not only the conductor layer 11 but also the dielectric layer 14 can be protected.

  The electromagnetic field generating element according to the present invention can be suitably used for an electromagnetic field generating element capable of performing optically assisted magnetic recording, a recording head including the same, and an information recording / reproducing apparatus.

It is a top view explaining the near field light generation | occurrence | production area | region when the electromagnetic field generation element which concerns on 1st embodiment of this invention, and the laser beam whose deflection | deviation direction is Y direction are irradiated. It is a top view explaining an electromagnetic field generating element concerning a first embodiment of the present invention and a near-field light generating region when a laser beam whose deflection direction is X direction is irradiated. FIG. 3 is a cross-sectional view of the recording head according to the first embodiment of the present invention viewed from the side. FIG. 3 is a plan view of the electromagnetic field generating element according to the embodiment of the present invention as viewed from the air outflow end side of the recording head. It is a top view explaining an electromagnetic field generating element concerning a second embodiment of the present invention and a near-field light generating region when a laser beam whose deflection direction is the Y direction is irradiated. It is sectional drawing of the recording head which concerns on 3rd embodiment of this invention. It is sectional drawing of the recording head which concerns on 3rd embodiment of this invention. It is a schematic diagram explaining the information recording / reproducing apparatus which concerns on 4th embodiment of this invention. It is a block diagram explaining the control part of the information recording / reproducing apparatus which concerns on 4th embodiment of this invention. It is a figure which shows the result of having simulated the intensity | strength of the near-field light when the electromagnetic field generation element which concerns on embodiment of this invention is irradiated with the laser beam whose deflection direction is a Y direction. It is a figure which shows the result of having simulated the intensity | strength of the near-field light when the electromagnetic field generating element which concerns on embodiment of this invention is irradiated with the laser beam whose deflection direction is X direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 'Electromagnetic field generating element 2,30,40,100 Recording head 10 Board | substrate 11 Conductor layer 12 Protective layer 12a 1st protective layer 12b 2nd protective layer 13 Suspension 14 Slit 15 Narrow part 16 Near field light generation part 17 Protection Layer boundary 20 Reproducing element 21, 22 Light source 200 Information recording / reproducing apparatus 201 Suspension 202 Arm 203 Actuator 204 Spindle 205 Information recording medium 300 Control unit 301 Control circuit 302 Spindle drive circuit 303 Position control circuit 304 Recording head drive circuit

Claims (10)

A substrate,
A slit formed on the substrate and made of a dielectric layer;
A conductor layer formed on the substrate and having a narrowed portion narrowed by the slit;
A protective layer formed on the conductor layer and the slit,
An electromagnetic field generating element that generates near-field light from the narrowed portion by irradiating the narrowed portion with light from a light source,
The protective layer is composed of a plurality of protective layers having different refractive indexes,
The electromagnetic field generating element, wherein a boundary between a first protective layer of the plurality of protective layers and a second protective layer different from the first protective layer is on the slit.   The electromagnetic field generating element according to claim 1, wherein a real part of a refractive index of the first protective layer is larger than a real part of a refractive index of the second protective layer. The real part of the refractive index of the first protective layer is greater than the real part of the refractive index of the slit;
3. The electromagnetic field generating element according to claim 1, wherein a real part of the refractive index of the second protective layer is smaller than a real part of the refractive index of the slit.   4. The electromagnetic field generating element according to claim 1, wherein the hardness of the protective layer is greater than the hardness of the slit and the conductor layer. 5.   The electromagnetic field generating element according to claim 1, wherein the slit is made of quartz.   The electromagnetic field according to any one of claims 1 to 5, wherein the first protective layer is made of titanium oxide, silicon nitride, or aluminum oxide, and the second protective layer is made of titanium nitride. Generating element.   The electromagnetic field generating element according to claim 1, wherein a semiconductor laser element is provided on the substrate.   A recording head comprising the electromagnetic field generating element according to claim 1 and a suspension.   9. An information recording / reproducing apparatus comprising: the recording head according to claim 8; an optically assisted magnetic recording medium; and a reproducing element for reproducing information recorded on the optically assisted magnetic recording medium.   The information recording / reproducing apparatus according to claim 9, wherein the reproducing element is provided on the substrate.

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