Thermally-assisted magnetic recording head, head gimbal assembly and magnetic recording device

A thermally-assisted magnetic recording head enables even steeper magnetization reversal between adjacent magnetic domains of a magnetic recording medium and satisfies the demand for high SN ratio and high recording density. The thermally-assisted magnetic recording head includes a pole that generates a writing magnetic field from an end surface that forms a part of an air bearing surface that opposes a magnetic recording medium, a waveguide through which light for exciting surface plasmon propagates, and a plasmon generator that couples to the light in a surface plasmon mode. The plasmon generator has a plane part and a projection part, the pole has a projection part opposing surface that opposes the projection part, and the distance between the projection part opposing surface and the projection part is 10-40 nm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a head that is used for a thermally-assisted magnetic recording that irradiates near-field light to a magnetic recording medium to decrease an anisotropy field of the magnetic recording medium and then performs data recording, and to a head gimbal assembly and a magnetic recording device to which the head is used.

2. Description of the Related Art

In the field of magnetic recording using a head and a medium, further performance improvements of thin film magnetic heads and magnetic recording media have been demanded in conjunction with a growth of high recording density of magnetic disk devices. Currently, composite type thin film magnetic heads are widely used for the thin film magnetic heads. The composite type thin film magnetic heads are configured with a configuration in which a magnetoresistive (MR) element for reading and an electromagnetic transducer element for writing are laminated.

The magnetic recording medium is a discontinuous medium in which magnetic nanoparticles gather and each of the magnetic nanoparticles has a single-magnetic-domain structure. In this magnetic recording medium, one recording bit is configured with a plurality of magnetic nanoparticles. Therefore, in order to increase recording density, asperities at a border between adjacent recording bits need to be reduced by decreasing the size of the magnetic nanoparticles. However, decreasing the size of the magnetic nanoparticles leads to a decrease in the volume of the magnetic nanoparticles, and thereby drawbacks that thermal stability of magnetizations in the magnetic nanoparticles decreases occur.

As a countermeasure against this problem, increasing magnetic anisotropy energy Ku of magnetic nanoparticles may be considered; however, the increase in Ku causes an increase in an anisotropy field (coercive force) of the magnetic recording medium. On the other hand, the upper limit of the writing magnetic field intensity of the thin film magnetic head is mostly determined by saturation magnetic flux density of a soft magnetic material configuring a magnetic core in the head. As a result, when the anisotropy field of the magnetic recording medium exceeds an acceptable value determined by the upper limit of the writing magnetic field intensity, it becomes impossible to perform writing. Currently, as a method to solve such thermal stability problem, a so-called thermally-assisted magnetic recording method has been proposed in which, while a magnetic recording medium formed of a magnetic material with large Ku is used, the magnetic recording medium is heated immediately before the application of a writing magnetic field so that the anisotropy field is reduced and the writing is performed.

As this thermally-assisted magnetic recording method, a method that uses a near-field light probe (a so-called plasmon-generator), which is a metal piece that generates near-field light from plasmon excited by laser light, is generally known.

As a magnetic recording head provided with such plasmon generator, a magnetic recording head provided with a pole, a waveguide, and a plasmon generator having a propagation edge opposing the waveguide has been already proposed by the inventors of the present application. Specifically, a magnetic recording head is proposed in which from the perspective of the air bearing surface side, heat dissipation layers respectively continue to trailing side end parts of a substantially V-shaped portion of the plasmon generator which has the substantially V-shaped part that is formed with a propagation edge positioned on the leading side and in which a part of the pole is contained in a space formed by the V-shaped part (U.S. patent application Ser. No. 13/046,117).

In this thermally-assisted magnetic recording head, light propagating through the waveguide is coupled with a plasmon generator in a surface plasmon mode to excite surface plasmon and then the surface plasmon propagates through the plasmon generator, so that the near-field light is generated at the near-field light generating portion positioned at an air bearing surface (ABS) side end part of the propagation edge. Furthermore, a magnetic recording medium is heated by the near-field light generated in the near-field light generating portion of the plasmon generator and a magnetic field is applied in a state where an isotropic magnetic field of the magnetic recording medium is reduced, and thereby information is written. In the above-described thermally-assisted magnetic recording head, a method that allows steep magnetization reversal between adjacent magnetic domains of the magnetic recording medium and that satisfies the demand for high recording density and high signal to noise (SN) ratio is shortening the distance between the center of near-field light irradiated to the magnetic recording medium and the center of the magnetic field applied from the pole, that is, in other word, shortening the distance between the near-field light generating portion and a tip end part (the end part positioned on the most leading side on the air bearing surface side) of the pole.

In order to shorten the distance between the near-field light generating portion and the tip end part of the pole in the magnetic recording head with the above-described configuration, it is necessary to thin the thickness of a substantially V-shaped part of the plasmon generator. However, with the thinned thickness, light is absorbed by the pole contacting the substantially V-shaped part, and this may reduce light intensity of the near-field light that emits from the near-field light generating portion. As a result, a preferred thermally-assisted effect may not be obtained. On the other hand, when the thickness of the substantially V-shaped part of the plasmon generator is thickened to obtain sufficient light intensity of the near-field light, the distance between the near-field light generating portion and the tip end part of the pole is lengthened, and this may bring difficulties to satisfy the demand for high recording density and high SN ratio.

In such a situation, due to the demand for even higher recording density in recent years, there is a current situation in which the demand for the thermally-assisted magnetic recording head has risen, the thermally-assisted magnetic recording head having a reduced spot size of near-field light irradiated to the magnetic recording medium to enable even steeper magnetization reversal between adjacent magnetic domains of the magnetic recording medium and satisfying the demand for higher SN ratio and higher recording density.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a thermally-assisted magnetic recording head that has a reduced spot size of near-field light irradiated to the magnetic recording medium to enable even steeper magnetization reversal between adjacent magnetic domains of a magnetic recording medium and that satisfies the demand for high SN ratio and high recording density, and a head gimbal assembly and a magnetic recording device using the thermally-assisted magnetic recording head.

In order to achieve the above object, the present invention provides a thermally-assisted magnetic recording head includes a pole that generates a writing magnetic field from an end surface that forms a part of an air bearing surface that opposes a magnetic recording medium, a waveguide through which light for exciting surface plasmon propagates, and a plasmon generator that couples to the light in a surface plasmon mode to generate near-field light from a near-field light generating end surface that forms a part of the air bearing surface, wherein the waveguide is arranged on a back side of the pole along a direction perpendicular to the air bearing surface from the perspective of the air bearing surface side, the plasmon generator has a plane part and a projection part that is projected from the plane part to the waveguide side and that opposes the pole and the waveguide with a predetermined gap therebetween, the pole has a projection part opposing surface that opposes the projection part, and the distance between the projection part opposing surface and the projection part is 10-40 nm (first invention).

For the first invention, it is preferred to include a nonmagnetic metal part that contacts the pole (second invention). For the second invention, it is preferred that another nonmagnetic metal part contacting the pole is included and that the nonmagnetic metal parts are arranged to contact both of the side surfaces of the pole in a track width direction from the perspective of the air bearing surface side (third invention), and that the nonmagnetic metal part contacts the plane part of the plasmon generator (fourth invention).

For the first invention, it is preferred that a light penetration suppression part that may suppress penetration of the near-field light is provided on the projection part opposing surface (fifth invention). For the fifth invention, it is preferred that the light penetration suppression part is a metal thin film with a thickness of 0.5-6.25 nm, and that the light penetration suppression part is configured of a metal material whose attenuation coefficient is larger than that of a metal material configuring the plasmon generator (seventh invention), and that the metal material that configures the light penetration suppression part is aluminum, magnesium, indium, or tin, or an alloy material including at least one type of these metals (eighth invention).

For the first invention, it is preferred that the projection part continues from the air bearing surface along the direction perpendicular to the air bearing surface (ninth invention).

For the first invention, it is possible that the shape of the projection part is a substantially trapezoidal shape that is surrounded by a short side that is positioned on the air bearing surface, a long side that is positioned on the back side with respect to the short side along the direction perpendicular to the air bearing surface and that is substantially parallel to the short side, and two inclined sides that respectively continue to end parts of the short side and end parts of the long side (tenth invention). In such a case, it is preferred that an angle formed by the direction perpendicular to the air bearing surface and one of the inclined sides is less than 10 degree (eleventh invention).

For the first invention, it is possible that the shape of the projection part includes a substantial V-shape formed by an apex that is positioned on the air bearing surface and two inclined sides that spread to each other from the apex toward the back side along the direction perpendicular to the air bearing surface (twelveth invention).

Further, the present invention provides a head gimbal assembly includes the thermally-assisted magnetic recording head discussed above, and a suspension that supports the thermally-assisted magnetic recording head (thirteenth invention).

Furthermore, the present invention provides a magnetic recording device includes a magnetic recording medium, the thermally-assisted magnetic recording head discussed above, and a positioning device that supports the thermally-assisted magnetic recording head and that also positions the thermally-assisted magnetic recording head with respect to the magnetic recording medium a magnetic recording medium (fourteenth invention).

According to the present invention, it is possible to provide a thermally-assisted magnetic recording head that has a reduced spot size of near-field light irradiated to the magnetic recording medium to enable even steeper magnetization reversal between adjacent magnetic domains of a magnetic recording medium and that satisfies the demand for high SN ratio and high recording density, and a head gimbal assembly and a magnetic recording device using the thermally-assisted magnetic recording head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to explaining embodiment of the present invention, terminologies used in the present specification are defined. In a lamination structure or an element structure formed on an element formation surface of a slider substrate of a magnetic recording head according to embodiment of the present invention, from a perspective of a reference layer or a reference element, a substrate side is referred to as “lower (below)” and an opposite side to the substrate side is referred to as “upper (above).” In addition, in the magnetic recording head according to embodiment of the present invention, “X, Y and Z axis directions” are defined in some of the drawings as necessary. Here, the Z axis direction corresponds to the above-described “up and down directions”, +Z side corresponds to a trailing side, and −Z side corresponds to a leading side. Moreover, the Y axis direction is a track width direction, and the X axis direction is a height direction

A thermally-assisted magnetic recording head according to one embodiment of the present invention is explained with reference to the drawings.

FIG. 1is a perspective view schematically illustrating a magnetic recording device of the present embodiment.FIG. 2is a perspective view schematically illustrating a head gimbal assembly (HGA) of the present embodiment.FIG. 3is a perspective view illustrating a thermally-assisted magnetic recording head according to the present embodiment.

As illustrated inFIG. 1, a magnetic disk device as a magnetic recording device in the present embodiment is provided with a number of magnetic disks301, an assembly carriage device310, head gimbal assemblies (HGA)312, and a control circuit330. The magnetic disks301rotate around a rotational shaft of a spindle motor302. The assembly carriage device310is provided with a plurality of drive arms311. Each of the HGAs312is attached to a tip portion of one of the drive arms311and has the thermally-assisted magnetic recording head1, which is a thin film magnetic head, according to the present embodiment. The control circuit330controls writing and reading operations of the thermally-assisted magnetic recording head1according to the present embodiment and controls a light emission operation of a laser diode, which is a light source that generates laser light for after-mentioned thermally-assisted magnetic recording.

In the present embodiment, the magnetic disk301is for perpendicular magnetic recording and has a structure in which a soft magnetic under layer, an intermediate layer, and a magnetic recording layer (perpendicular magnetization layer) are sequentially laminated above a disk substrate.

The assembly carriage device310is a device for positioning the thermally-assisted magnetic recording head1above a track, the track being formed in the magnetic disk301and having recording bits arrayed. In the assembly carriage device310, the drive arms311are stacked in a direction along a pivot bearing shaft313and are angularly swingable by a voice coil motor (VCM)314centering around the pivot bearing shaft313.

Note, the structure of the magnetic disk device of the present embodiment is not limited to the above-described structure but may include only a single piece of each of the magnetic disk301, the drive arm311, the HGA312, and the thermally-assisted magnetic recording head1.

In the HGA312illustrated inFIG. 2, a suspension320includes a load beam321, a flexure322that is firmly attached to the load beam321and has elasticity, and a base plate323provided at a base of the load beam321. In addition, a wiring member324is provided on the flexure322. The wiring member324is formed from a lead conductor and connection pads that are electrically connected to both sides of the lead conductor. The thermally-assisted magnetic recording head1according to the present embodiment is firmly attached to the flexure322at a tip end portion of the suspension320so as to oppose a surface of each of the magnetic disks301with a predetermined gap (flying height). Further, an end of the wiring member324is electrically connected to a terminal electrode of the thermally-assisted magnetic recording head1according to the present embodiment. Additionally, the structure of the suspension320in the present embodiment is also not limited to the above-described structure, and a head drive IC chip (not illustrated) may be mounted in the middle of the suspension320.

As illustrated inFIG. 3, the thermally-assisted magnetic recording head1according to the present embodiment is provided with a slider10and a light source unit50. The slider10is formed of ALTIC (Al2O3—TiC) or the like and is provided with a slider substrate11having an air bearing surface (ABS)11aand a head part12. The ABS11aas a medium opposing surface is processed to obtain an appropriate flying height, and the head part12is formed on an element formation surface11bperpendicular to the ABS11a.

Furthermore, the light source unit50is formed of ALTIC (Al2O3—TiC) or the like, and is provided with a unit substrate51having a joining surface51a, and a laser diode60as a light source, the laser diode60being provided on a light source installation surface51bperpendicular to the joining surface51a.

Here, the slider10and the light source unit50are joined with each other such that a back surface11cof the slider substrate11contacts the joining surface51aof the unit substrate51. The back surface11cof the slider substrate11means an end surface of the slider substrate11on the opposite side to the ABS11a. Note, the thermally-assisted magnetic recording head1according to the present embodiment may have a configuration in which the laser diode60is directly mounted on the slider10without using the light source unit50.

The head part12formed on the element formation surface11bof the slider substrate11is provided with a head element20, a waveguide23, a plasmon generator24, a protective layer31, a pair of first terminal electrodes25a, and a pair of second terminal electrodes25b. The head element20has an MR element21for reading out data from the magnetic disk301and an electromagnetic transducer element22for writing data to the magnetic disk301. The waveguide23is disposed for guiding laser light from the laser diode60provided on the light source unit50to an ABS side. The plasmon generator24configures a near-field light generating optical system with the waveguide23. The protective layer31is formed on the element formation surface11bso as to cover the MR element21, the electromagnetic transducer element22, the waveguide23, and the plasmon generator24. The pair of first terminal electrodes25ais exposed on an upper surface of the protective layer31and is electrically connected to the MR element21. The pair of second terminal electrodes25bis exposed on the upper surface of the protective layer31and is electrically connected to the electromagnetic transducer element22. The first and second terminal electrodes25aand25bare electrically connected to the connection pad of the wiring member324provided to the flexure322(seeFIG. 2).

One end of the MR element21, one end of the electromagnetic transducer element22, and one end of the plasmon generator24respectively reach a head part end surface12a, which is the air bearing surface of the head part12. Here, the head part end surface12aand the ABS11aform the medium opposing surface (or air bearing surface) of the entire thermally-assisted magnetic recording head1according to the present embodiment.

During the actual writing and reading, the thermally-assisted magnetic recording head1hydro-dynamically flies above the surface of the rotating magnetic disk301at a predetermined flying height. At this time, the end surfaces of the MR element21and the electromagnetic transducer element22oppose the surface of the magnetic recording layer of the magnetic disk301maintaining an appropriate magnetic spacing therebetween. In this state, the MR element21performs the reading by sensing a data signal magnetic field from the magnetic recording layer, and the electromagnetic transducer element22performs the writing by applying a data signal magnetic field to the magnetic recording layer.

At the time of the writing, the laser light that has propagated from the laser diode60of the light source unit50through the waveguide23is coupled with the plasmon generator24in a surface plasmon mode and excites surface plasmon at the plasmon generator24. This surface plasmon propagates through a projection part241(seeFIG. 4), which will be described later, of the plasmon generator24toward the head part end surface12aso that near-field light is generated at an end part of the plasmon generator24on a head part end surface12aside. This near-field light reaches the surface of the magnetic disk301and heats a portion of the magnetic recording layer of the magnetic disk301. As a result, anisotropy field (coercive force) at that portion decreases to a value at which the writing becomes possible. It becomes able to perform the thermally-assisted magnetic recording by applying a writing magnetic field to the portion where the anisotropy field has decreased.

FIG. 4is a cross-sectional view of the A-A line (XZ plane) inFIG. 3, and schematically illustrates a configuration of the thermally-assisted magnetic recording head1according to the present embodiment.

As illustrated inFIG. 4, the MR element21has a lower shield layer21aformed on a first insulating layer32aon the element formation surface11bof the slider substrate11, an MR multilayer body21bformed on the lower shield layer21a, and an upper shield layer21cformed on the MR multilayer body21b. A second insulating layer32bis provided between the lower shield layer21aand the upper shield layer21cin the periphery of the MR multilayer body21b. The lower shield layer21aand the upper shield layer21cprevent the MR multilayer body21bfrom receiving the effects of external magnetic fields which are noise.

The lower shield layer21aand the upper shield layer21care magnetic layers with a thickness of approximately 0.5-3 μm formed by, for example, a frame plating method, a spattering method, or the like of a soft magnetic material such as, for example, NiFe (permalloy), FeSiAl (sendust), CoFeNi, CoFe, FeN, FeZrN, CoZrTaCr, etc., a multilayer film formed of these materials, or the like.

The MR multilayer body21bis a magnetically sensitive part that senses a signal magnetic field using the MR effect and may be any one of a current in plane-giant magnetoresistive (CIP-GMR) multilayer body that uses a current in plane-giant magnetoresistive effect, a current perpendicular to plane-giant magnetoresistive (CPP-GMR) multilayer body that uses a current perpendicular to plane-giant magnetoresistive effect, and a tunnel-magnetoresistive (TMR) multilayer body that uses a tunnel-magnetoresistive effect. When the MR multilayer body21bis a CPP-GMR multilayer body or a TMR multilayer body, the lower shield layer21aand the upper shield layer21calso function as electrodes. On the other hand, when the MR multilayer body21bis a CIP-GMR multilayer body, insulating layers are provided respectively between the MR multilayer body21band the lower shield layer21aand between the MR multilayer body21band the upper shield layer21c. Moreover, an MR lead layer that is electrically connected to the MR multilayer body21bis provided.

When the MR multilayer body21bis a TMR multilayer body, the MR multilayer body21bhas a structure in which the following are sequentially laminated: an antiferromagnetic layer formed of, for example, IrMn, PtMn, NiMn, RuRhMn, or the like having a thickness of approximately 5-15 nm; a magnetization pinned layer that has a structure in which two ferromagnetic layers formed of, for example, CoFe or the like sandwich a nonmagnetic metal layer formed of Ru or the like and that has a magnetization direction pinned by the antiferromagnetic layer; a tunnel barrier layer formed of a nonmagnetic dielectric material that is a metal film formed of Al, AlCu, or the like having a thickness of approximately 0.5-1 nm oxidized by oxygen introduced into a vacuum device or by natural oxidation; and a magnetization free layer that is configured with a double layer film formed of a layer of CoFe or the like, which is a ferromagnetic material, having a thickness of approximately 1 nm and a layer of NiFe or the like, which is a ferromagnetic material, having a thickness of approximately 3-4 nm and that achieves tunnel exchange coupling with the magnetization pinned layer through the tunnel barrier layer therebetween.

The head part12in the present embodiment is provided with a third insulating layer32cprovided on the upper shield layer21c, an interelement shield layer33provided on the third insulating layer32c, and a fourth insulating layer32dprovided on the interelement shield layer33. The interelement shield layer33may be formed of a soft magnetic material, and has a function of shielding the MR element21from the magnetic field generated at the electromagnetic transducer element22provided on the fourth insulating layer32d. Note, the third insulating layer32cand the interelement shield layer33may be omitted.

The electromagnetic transducer element22for the perpendicular magnetic recording is provided with a lower yoke layer22aprovided on the fourth insulating layer32d, a writing coil22bprovided on the lower yoke layer22a, a pole22cthat is provided above the writing coil22band that reaches the head part end surface12aso as to form a part of the head part end surface12a, an upper yoke layer22dprovided above the pole22c, two linkage parts22eand22e(seeFIG. 7) that are provided on the lower yoke layer22aso as to sandwich the waveguide23, which will be described later, from both sides in the Y axis direction (track width direction) and to link the lower yoke layer22aand the upper yoke layer22d. The writing coil22bhas a spiral structure in which the writing coil22bwounds around two linkage layers22eand22e(seeFIG. 7) so as to at least go across between the lower yoke layer22aand the upper yoke layer22dduring one turn.

The head part12in the present embodiment is provided with a fifth insulating layer32eprovided on the fourth insulating layer32din the vicinity of the lower yoke layer22a, a sixth insulating layer32fprovided on the lower yoke layer22aand the fifth insulating layer32e, a seventh insulating layer32gprovided between the winding lines of the writing coil22band in its vicinity, an eighth insulating layer32hprovided on the writing coil22band the seventh insulating layer32g, and a ninth insulating layer32iprovided on the eighth insulating layer32hin the vicinity of the plasmon generator24, which will be described later.

In the head part12in the present embodiment, the lower yoke layer22a, the linkage layers22e, the upper yoke layer22d, and the pole22cform a magnetic guide path that allows a magnetic flux corresponding to a magnetic field generated by the writing coil22bto pass through and that guides the magnetic flux to the magnetic recording layer (perpendicular magnetization layer) of the magnetic disk301. The furthest leading side of the end surface220of the pole22cthat forms a part of the head part end surface12ais the point that generates a writing magnetic field.

The pole22cis preferably formed of a soft magnetic material having a higher saturation magnetic flux density than that of the upper yoke layer22d, and is formed of a soft magnetic material such as, for example, FeNi, FeCo, FeCoNi, FeN, FeZrN, or the like, which are iron-based alloy materials having Fe as a primary component. Note, the thickness of the pole22cin the Z axis direction may be set to be 0.1-0.8 μm.

Furthermore, the width of the pole22cin the Y axis direction is preferably 0.2-0.3 μm. When the width of the pole22cin the Y axis direction is within the above-described range, a magnetic field having a writable intensity can be appropriately applied to the heating spot of the magnetic disk301that is heated by the plasmon generator24. Furthermore, the thickness of the pole22cin the X axis direction (height direction) is preferably thin to the extent possible and is preferably 0.06-0.3 μm. When the thickness of the pole22cis thinned, this enables the distance MO (seeFIG. 5) to be shortened (10-40 nm) and, in parallel, enables the spot diameter of near-field light irradiated to the magnetic disk301to be small. The distance MO is the distance on the head part end surface12abetween the pole22cand the projection part241(upper surface of the projection part) of the plasmon generator24. Therefore, the demands for high SN ratio and high recording density can be satisfied together.

The end surface of the upper yoke layer22don the head part end surface12aside does not reach the head part end surface12a, and is provided at a recessed position at a predetermined distance from the head part end surface12atoward the head part back end surface12bside in the X axis direction. Thereby, magnetic flux can be focused at the pole22c, and the intensity of a magnetic field generated from the pole22ccan be strengthened.

The writing coil22bis formed of a conductive material such as Cu (copper) or the like. Note, the writing coil22dis a single layer in the present embodiment; however, may be two or more layers or may be a helical coil arranged so as to sandwich the upper yoke layer22d. Furthermore, the winding number of the writing coil22bis not particularly limited, and can be set to 2-7 turns, for example.

The lower yoke layer22ais formed on the forth insulating layer32dformed of an insulation material such as Al2O3(alumina), and functions as a magnetic guide path that guides a magnetic flux that has returned from a soft magnetic under layer provided under the magnetic recording layer (perpendicular magnetization layer) of the magnetic disk301. The lower yoke layer22ais formed of a soft magnetic material and has a thickness of approximately 0.5-5 μm, for example.

The waveguide23is provided at a recessed position from the pole22cin the X axis direction (height direction) from the perspective of the ABS11a(the head part end surface12a). The plasmon generator24is provided below the pole22c(on the leading side). The waveguide23and the plasmon generator24form an optical system for generating near-field light in the head part12.

The waveguide23is elongated in parallel with the element formation surface11bfrom a rear end surface23athat forms a part of a head part rear end surface12btoward a rear end surface of the pole22c, and a predetermined gap is between the rear end surface of the pole22cand an end surface23bso that the waveguide23does not contact the pole22c. Also, a lower surface (a part of side surfaces) of the waveguide23and a part of the projection part241of the plasmon generator24oppose each other with a predetermined gap therebetween, and the portion sandwiched by these is a buffer portion40with a lower refractive index than the refractive index of the waveguide23.

The buffer portion40functions to couple laser light propagating through the waveguide23with the plasmon generator24in the surface plasmon mode. Note, the buffer portion40may be a part of the ninth insulating layer32ior may be another layer provided separately from the ninth insulating layer32i.

The plasmon generator24is provided such that the projection part241opposes both the pole22cand the waveguide23. Note, the specific configurations of the pole22c, the waveguide23, and the plasmon generator24are described later.

As illustrated inFIG. 4, the light source unit50is provided with the unit substrate51, the laser diode60provided on the light source installation surface51bof the unit substrate51, a first drive terminal electrode61electrically connected to an electrode60fthat forms a lower surface of the laser diode60, and a second drive terminal electrode62electrically connected to an electrode60ethat forms an upper surface of the laser diode60. The first and second drive terminal electrodes61and62are electrically connected to the connection pad of the wiring member324provided on the flexure322(seeFIG. 2). When a predetermined voltage is applied to the laser diode60from the first and second drive terminal electrodes61and62, laser light is radiated from an emission center60hpositioned on an emission surface of the laser diode60. Here, in the head structure illustrated inFIG. 4, an oscillation direction of an electric field of laser light that the laser diode60generates is preferably perpendicular to a lamination layer surface of an active layer60d(in the Z axis direction). That is, it is preferable that laser light that the laser diode60generates is a TM-mode polarized light. As a result, laser light propagating through the waveguide23becomes able to be properly coupled with the plasmon generator24in the surface plasmon mode through the buffer portion40.

As the laser diode60, it is possible to use a diode that is generally used for communication, optical disk storage, material analysis or the like such as InP-type, GaAs-type, and GaN-type diodes etc. The wavelength λLof laser light to radiate need only be in the range of 375 nm-1.7 μm, for example.

Specifically, it is also possible to use an InGaAsP/InP quaternary mixed crystal type laser diode, of which the available wavelength region is set to be 1.2-1.67 μm, for example. The laser diode60has a multilayered structure that includes an upper electrode60e, the active layer60c, and a lower electrode60f. Reflection layers for exciting oscillation by total reflection are formed on the front and back of cleavage surfaces of this multilayered structure. In a reflection layer60g, an aperture is provided at a position of the active layer60cthat includes the emission center60h. It is possible to set the thickness TLAof the laser diode60to be approximately 60-200 μm, for example.

Also, it is possible to use a power source in the magnetic disk device for driving the laser diode60. In actual, magnetic disk devices normally is provided with a power source of approximately 5V, for example, and therefore a sufficient voltage for a laser oscillation operation is maintained. In addition, power consumption of the laser diode60is approximately several tens of mW, for example, and therefore the power source in the magnetic disk device can sufficiently cover the power. In actual, the power source applies a predetermined voltage to the middle of the first drive terminal electrode61that is electrically connected to the lower electrode60fand the second drive terminal electrode62that is electrically connected to the upper electrode60eto oscillate the laser diode60, and thereby the laser light is radiated from the aperture including the emission center60hin the reflection layer60g. Note, the laser diode60and the first and second drive terminal electrodes61and62are not limited to the above-described embodiment. For example, the electrodes may be positioned in a vertically reversed manner in the laser diode60, and the upper electrode60emay be joined to the light source installation surface51bof the unit substrate51. Also, it is possible to optically connect the laser diode and the waveguide23with each other by installing the laser diode on the element formation surface11bof the thermally-assisted magnetic recording head1. Moreover, it is possible for thermally-assisted magnetic recording head1to be provided without the laser diode60and to have the emission center of a laser diode provided in the magnetic disk device and the rear end surface23aof the waveguide23that are connected with each other by an optical fiber or the like, for example.

The sizes of the slider10and the light source unit50are arbitrary; however, for example, the slider10may be also a so-called femto slider having a width of 700 μm in the track width direction (Y axis direction), a length of 850 μm (in Z axis direction), and a thickness of 230 μm (in X axis direction). In this case, the size of the light source unit50may be smaller than the size of the slider and may have a width of 425 μm in the track width direction, a length of 300 μm, and a thickness of 300 μm, for example.

By connecting the above-described light source unit50and slider10, the thermally-assisted magnetic recording head1is configured. In this connection, the joining surface51aof the unit substrate51and the back surface11cof the slider substrate11contacte each other. At this time, the position of the unit substrate51and the position of the slider substrate11are determined such that the laser light generated from the laser diode60enters into the rear end surface23aof the waveguide23that is on the side opposite to the ABS11a.

FIG. 5is a plan view from the perspective of the air bearing surface side, the view mainly schematically illustrating a configuration of the waveguide23, the plasmon generator24, and the pole22cin the thermally-assisted magnetic recording head1according to the present embodiment.FIG. 6is a partially-enlarged-cross-sectional view (partially-enlarged view of the cross-section (XZ plane) ofFIG. 4) mainly schematically illustrating a configuration of the waveguide23, the plasmon generator24, and the pole22cin the thermally-assisted magnetic recording head1according to the present embodiment.

As illustrated inFIG. 5, the thermally-assisted magnetic recording head1according to the present embodiment has nonmagnetic metal parts NM and NM respectively contacting both side surfaces of the pole22cin the Y axis direction (track width direction) from the perspective of the head part end surface12aside. The contacting of the nonmagnetic metal parts NM and NM with the pole22callows the nonmagnetic metal parts NM and NM to function as heatsinks, and thereby an excessive temperature increase in the pole22ccan be suppressed. Furthermore, the provision of the nonmagnetic metal parts NM and NM on the both sides of the pole22cin the Y axis direction (track width direction) from the perspective of the head part end surface12aside enables to suppress diffusion of near-field light toward the Y axis direction (track width direction), the near-field light being generated from the projection part241of the plasmon generator24, and to further reduce the spot diameter of the near-field light irradiated to the magnetic disk301.

The nonmagnetic metal part NM and NM may be provided in a non-contacting manner with a plane part240of the plasmon generator24; however, are preferably provided in a contacting manner with the plane part240. The contacting of the nonmagnetic metal parts NM and NM with the plane part240of the plasmon generator24can also suppress an excessive temperature increase in the plasmon generator24.

Given as a material for configuring the nonmagnetic metal part NM is, for example, Au, Cu, Ag, Al, Pt, W, or Ru, or an alloy made of at least one type of these, etc.

Lengths of the nonmagnetic metal part NM in the X axis direction (height direction), in the Y axis direction (track width direction), and in the Z axis direction are, as long as the excessive temperature increase in the pole22ccan be suppressed and moreover as long as diffusion toward the Y axis direction (track width direction) of near-field light generated from the projection part241of the plasmon generator24can be suppressed, not particularly limited and may be arbitrarily set. For example, length of the nonmagnetic metal part NM in the X axis direction (height direction) may be set to be 100-3,000 nm; length in the Y axis direction (track width direction) may be set to be 200-10,000 nm; length in the Z axis direction may be set to be 100-1,000 nm.

As illustrated inFIG. 6, in the thermally-assisted magnetic recording head1according to the present embodiment, the pole22chas a projection part opposing surface22c1that opposes the projection part241(upper surface of the projection part), the ninth insulating layer32iis intervened between the pole22cand the projection part241(upper surface of the projection part) of the plasmon generator24, and a light penetration suppression part26is provided on the projection part opposing surface22c1. By the light penetration suppression part26provided, even when light (electromagnetic field) propagating through the projection part241of the plasmon generator24attempts to go into the light penetration suppression part26toward the pole22c, the light cannot go into the light penetration suppression part26due to high skin effect of the light penetration suppression part26. As a result, light peak intensity of near-field light irradiated to the magnetic disk301can be increased.

The light penetration suppression part26is preferably configured of a metal material whose attenuation coefficient is larger than that of a metal material configuring the plasmon generator24. When the light penetration suppression part26is configured of a metal material whose attenuation coefficient is larger than that of a metal material (for example, Au (attenuation coefficient to light with wavelength of 800 nm; k=4.9), Ag (attenuation coefficient to light with wavelength of 800 nm; k=5.2), or the like) configuring the plasmon generator24, penetration of light (electromagnetic field) into the light penetration suppression part26, the light propagating through the projection part241, is suppressed. Examples of such metal materials are Al (attenuation coefficient to light with wavelength of 800 nm; k=8.1), Mg (attenuation coefficient to light with wavelength of 800 nm; k=8.0), In (attenuation coefficient to light with wavelength of 800 nm; k=6.6), and Sn (attenuation coefficient to light with wavelength of 800 nm; k=7.3), and an alloy made of at least one type of above-mentioned metals.

Thickness TLPI(thickness in the Z axis direction) of the light penetration suppression part26is preferably 0.5-6.25 nm, and more preferably 1.25-5.5 nm. When the thickness is less than 0.5 nm, light penetration suppression effect by the light penetration suppression part26may not be sufficient; when the thickness is in excess of 6.25 nm, increase of the light penetration suppression effect is rarely observed, and thereby the distance between the pole22cand the projection part241is increased, which is not preferred.

A distance MO, which is on the head part end surface12abetween the pole22cand the projection part241(upper surface of the projection part) of the plasmon generator24, is 10-40 nm, and preferably 15-30 nm. When the distance MO is less than 10 nm, near-field light may be absorbed by the pole22cand reflect off the pole22c, so that a near-field light peak intensity sufficient to heat the magnetic disk301may not be obtained. When the distance MO is in excess of 40 nm, the distance between the center of a magnetic field applied to the magnetic disk301and the center of near-field light irradiated is increased, so that the demand for high SN ratio becomes unable be satisfied. In other words, when the distance MO is in the above-described range, near-field light, which is generated from a near-field light generating portion NFP (seeFIGS. 5-7) of the plasmon generator24and which diffuses toward the magnetic pole22cside, is suppressed by the existence of the pole22c. Therefore a spot diameter of light irradiated to the magnetic disk301can be reduced and, in parallel, demands for high recording density and high SN ratio can be satisfied.

The waveguide23is provided in the back side of the pole22calong the direction perpendicular to the head part end surface12aso as to be hidden by the pole22cfrom the perspective of the head part end surface12aside. The provision of the waveguide23in such position enables to set the distance MO, which is on the head part end surface12between the pole22cand the projection part241(upper surface of the projection part) of the plasmon generator24, within the above-described range, and also to set the distance between the waveguide23and the projection part241(upper surface of the projection) opposing the waveguide23at such a degree that makes possible for laser light propagating through the waveguide23to couple to the projection part241of the plasmon generator24in the surface plasmon mode.

FIG. 7is a perspective view schematically illustrating a configuration of the waveguide23, the plasmon generator24, and the pole22cin the thermally-assisted magnetic recording head1according to the present embodiment. InFIG. 7, the head part end surface12aincluding a portion from which a writing magnetic field and near-field light are radiated to the magnetic recording medium is positioned on the left side.

As illustrated inFIG. 7, the thermally-assisted magnetic recording head1according to the present embodiment is provided with the waveguide23for propagating laser light63for generating near-field light, and the plasmon generator24that includes the projection part241through which the surface plasmon excited by the laser light (waveguide light)63propagates. The projection part241opposes the lower surface of the waveguide23with a predetermined gap therebetween.

The plasmon generator24is provided with a near-field light generating end surface24athat reaches the head part end surface12a. Additionally, the portion that is sandwiched by a portion of an side surface of the waveguide23and a portion of an upper surface (side surface) of the plasmon generator24including the projection part241forms a buffer portion40(seeFIG. 4). In other words, a portion of the projection part241is covered by the buffer portion40. The buffer portion40functions to couple the laser light (waveguide light)63with the plasmon generator24in the surface plasmon mode. Additionally, the projection part241functions to propagate the surface plasmon excited by the laser light (waveguide light)63to the near-field light generating end surface24a.

Note, side surfaces of the waveguide23refer end surfaces out of end surfaces surrounding the waveguide23, excluding the end surface23b(seeFIG. 6) positioned on the head part end surface12aside and the rear end surface23aopposite to the end surface23b. The side surfaces of the waveguide23are the surfaces on which the laser light (waveguide light)63may totally reflect, the light propagating through the waveguide23, and herein the waveguide23corresponds to a core. In the present embodiment, the side surface of the waveguide23having a portion contacting the buffer portion40is a lower surface of the waveguide23.

More specifically, the laser light (waveguide light)63that has propagated to the vicinity of the buffer portion40is coupled with the optical configuration of the waveguide23having a predetermined refractive index nWG, the buffer portion40having a predetermined refractive index nBF, and the plasmon generator24made of a conductive material such as a metal or the like, and thereby the surface plasmon mode at the projection part241of the plasmon generator24is induced. In other words, the laser light (waveguide light)63is coupled with the plasmon generator24in the surface plasmon mode. It becomes possible to achieve this induction of the surface plasmon mode when the refractive index nBFof the buffer portion40is set to be smaller than the refractive index nWGof the waveguide23(nBF<nWG). Actually, evanescent light is excited in the buffer portion40based on the optical interfacial condition between the waveguide23, which is the core, and the buffer portion40. Then, the surface plasmon mode is induced such that the evanescent light and a fluctuation of charges excited on the surface (projection part241) of the plasmon generator24are coupled with each other, and surface plasmon70is excited (seeFIG. 9). Herein, the projection part241is in the closest position to the waveguide23and also the width in the Y axis direction is extremely small, so that an electrical field is more likely to be concentrated. Accordingly, the surface plasmon70is more likely to be excited.

A gap G (seeFIG. 9) between the lower surface of the waveguide23(surface opposite to the plasmon generator24) and the upper surface of the projection part241of the plasmon generator24(surface opposite to the waveguide23) is preferably 15-40 nm, and further preferably 25-30 nm. When the gap G is within the above-described range, it is possible to increase light density and to decrease the light spot diameter of near-field light irradiated to the magnetic disk301.

As illustrated inFIG. 7, the plasmon generator24has a plane part240and the projection part241that is projected from the plane part240to the waveguide23side, and an end surface that forms a part of the head part end surface12ais the near-field light generating end surface24a.

A portion of the projection part241opposes the waveguide23with the buffer portion40therebetween, and is elongated to the near-field light generating end surface24a. Thereby, the projection part241can realize the function of propagating the surface plasmon excited by the laser light (waveguide light) that has propagated through the waveguide23. In other words, the plasmon generator24couples to the waveguide light in the surface plasmon mode so as to propagate the surface plasmon on the projection part241. As a result, near-field light is generated from the near-field light generating portion NFP on the near-field light generating end surface24a.

The projection height TPGCof the projection part241is preferably 15-45 nm. Also, the width WPGCof the near-field light generating end surface24aof the projection part241in the Y axis direction is smaller than the wavelength of the laser light (waveguide light)63, and is preferably 15-30 nm. Also, from the perspective of the air bearing surface side where the waveguide23is positioned on the trailing side with respect to the plasmon generator24, the height TPGfrom a lower end of the plane part240to the upper end (upper surface) of the projection part241is preferably 65-205 nm, and further preferably approximately 130 nm. Furthermore, the length HPGof the plasmon generator24in the X axis direction is preferably 1.0-1.4 μm, and further preferably approximately 1.2 μm. When the plasmon generator24and the projection part241have the above-described size, it is possible to decrease the light spot diameter of near-field light irradiated to the magnetic disk301.

In the present embodiment, the shape of the upper surface of the projection part241is a rectangle; however, is not limited to this shape. For example, as illustrated inFIG. 8A, the shape of the upper surface of the projection part241may be a trapezoidal shape that is formed by a short side positioned on the head part end surface12a, a long side positioned on the head part rear end surface12bside, and two inclined sides that respectively connect end parts of the sides. Therein, the width in the Y axis direction gradually gets wider as approaching from the head part end surface12atoward the head part rear end surface12bside. Also, as illustrated inFIG. 8B, the shape of the upper surface of the projection part241may be the shape where the width in the Y axis direction gradually gets wider as approaching from the head part end surface12atoward the back side in the X axis direction to a predetermined position and gets constant from the predetermined position to the head part rear end surface12bside. Furthermore, as illustrated inFIG. 8C, the shape of the upper surface of the projection part241may be also a substantially triangular shape where its apex is positioned on the head part end surface12aand the width in the Y axis direction gradually gets wider as approaching toward the head part rear end surface12bside. When the shape of the upper surface of the projection part241is any one of the above-described shapes, it is possible to increase the light density of near-field light irradiated to the magnetic disk301and to reduce the light spot diameter. As illustrated inFIG. 8A, the angles θ formed respectively by the two inclined sides of the trapezoid in the upper surface of the projection part241and the X axis are preferably less than 10 degree, further preferably 1-3 degree, and extremely preferably approximately 2 degree.

The plane part240of the plasmon generator24can function to release heat generated at the near-field light generating portion NFP on the near-field light generating end surface24aof the plasmon generator24from the near-field light generating portion NFP. As a result, this can contribute to suppress the excessive temperature increase in the plasmon generator24and to prevent an unnecessary projection of the near-field light generating end surface24aand a significant reduction in light usage efficiency of the plasmon generator24.

The plasmon generator24is preferably formed of a conductive material such as a metal (e.g., Pd (attenuation coefficient to light with wavelength of 800 nm; k=5.1); Pt (attenuation coefficient to light with wavelength of 800 nm; k=5.0), Rh (attenuation coefficient to light with wavelength of 800 nm; k=6.8), Ir (attenuation coefficient to light with wavelength of 800 nm; k=5.3), Ru (attenuation coefficient to light with wavelength of 800 nm; k=5.2), Au (attenuation coefficient to light with wavelength of 800 nm; k=4.9), Ag (attenuation coefficient to light with wavelength of 800 nm; k=5.2), or Cu (attenuation coefficient to light with wavelength of 800 nm; k=5.1)), or an alloy formed of at least two types selected from these metals, and is further preferably formed of a material whose attenuation coefficient is smaller than that of a metal material configuring the light penetration suppression part26.

The waveguide23is provided in a position recessed more than the pole22cin the X axis direction (height direction) with a predetermined gap from the rear end surface22c2(seeFIG. 6) of the pole22c. Then, between the rear end surface22c2of the pole22cand the end surface23b(seeFIG. 6) of the waveguide23, the insulating layer32j(seeFIG. 6) is provided. With such configuration, the waveguide23and the pole22ccan be positionally separated from each other. As a result, a case can be avoided, in which a portion of the laser light (waveguide light)63is absorbed by the pole22cformed of a metal so that the amount of light to be transduced to the near-field light decreases.

Regarding the shape of the waveguide23, the width in the track width direction (Y axis direction) may be constant; however, as illustrated inFIG. 5andFIG. 7, the width may guradually get wider as approaching from the end surface23bof the waveguide23toward the back side in the X axis direction (height direction). The width in the track width direction (Y axis direction) of the rear end surface23aof the waveguide23may be, for example, approximately 0.5-20 μm; the width in the track width direction (Y axis direction) of the end surface23bmay be, for example, approximately 0.3-10 μm; the thickness in the Z axis direction may be approximately 0.1-4 μm; the length in the X axis direction may be, for example, approximately 10-300 μm.

The upper surface of the waveguide23contacts the protective layer31(seeFIG. 4); the lower surface of the waveguide23and both end surfaces in the track width direction (Y axis direction) of the waveguide23contact the ninth insulating layer32i(seeFIG. 4). Herein, the waveguide23is configured of a material with a refractive index nWGthat is higher than a refractive index nISof the configuration material of the ninth insulating layer32iand the protective layer. For example, in case where the wavelength λLof laser light is 600 nm when the ninth insulating layer32iand the protective layer31are formed of SiO2(silicon dioxide; n=1.46), the waveguide23may be formed of Al2O3(alumina; n=1.63). Furthermore, when the ninth insulating layer32iand the protective layer31are formed of Al2O3(n=1.63), the waveguide23may be formed of SiOxNy(n=1.7-1.85), Ta2O5(n=2.16), Nb2O5(n=2.33), TiO (n=2.3-2.55) or TiO2(n=2.3-2.55). When the waveguide23is formed of such materials, propagation loss of the laser light (waveguide light)63can be suppressed low due to excellent optical characteristics that the materials themselves have. Further, while the waveguide23functions as a core, the ninth insulating layer32iand the protective layer31function as a cladding, so that the total reflection condition on all of the side surfaces is established. As a result, more laser light (waveguide light)63reaches the position of the buffer portion40, and the propagation efficiency of the waveguide23increases.

Further, the waveguide23may have a multilayered structure of dielectric materials. In the multilayered structure, the closer portion to the plasmon generator24the layers are positioned in, the higher the refractive index n becomes. For example, such a multilayered structure is realized by sequentially laminating dielectric materials whose value of a composition ratio (X, Y) in SiOxNyis appropriately varied. The number of laminated layers may be 8-12 layers, for example. As a result, when the laser light (waveguide light)63is linearly polarized light in the Z axis direction, it becomes possible to propagate the laser light (waveguide light)63farther toward the buffer portion40side in the Z axis direction. At that time, by selecting the composition of each layer in the multilayered structure, the layer thickness, and the number of layers, the preferred propagation position for the laser light (waveguide light)63in the Z axis direction can be obtained.

The buffer portion40is formed of a dielectric material having a refractive index nBFthat is lower than the refractive index nWGof the waveguide23. For example, when the wavelength λLof the laser light is 600 nm and the waveguide23is formed of Al2O3(alumina; n=1.63), the buffer portion40may be formed of SiO2(silicon dioxide; n=1.46). In addition, when the waveguide23is formed of Ta2O5(n=2.16), the buffer portion40may be formed of SiO2(n=1.46) or Al2O3(n=1.63). In these cases, the buffer portion40may be configured as a part of the ninth insulating layer32i(seeFIG. 4) formed of SiO2(n=1.46) or Al2O3(n=1.63) and functioning as a cladding. Moreover, the length LBF(seeFIG. 9) in the X axis direction of the buffer portion40, which is a portion sandwiched by the lower surface of the waveguide23and the projection part241, is preferably 0.5-5 μm and is preferably larger than the wavelength λLof the laser light (waveguide light)63. In this case, the buffer portion40has a significantly larger region compared to the so-called “focal region” formed when the laser light is focused at the buffer portion40and the plasmon generator24for being coupled in the surface plasmon mode. This enables extremely stable coupling in the surface plasmon mode. The thickness TBF(seeFIG. 9) in the Z axis direction of the buffer portion40is preferably 10-200 nm. These length LBFand thickness TBFof the buffer portion40are important parameters for obtaining appropriate excitation and propagation of the surface plasmon.

Next, the description is given of the function of the thermally-assisted magnetic recording head1having the above-described configuration according to the present embodiment.FIG. 9is a schematic view for explaining thermally-assisted magnetic recording that uses a surface plasmon mode in the thermally-assisted magnetic recording head1according to the present embodiment.

As illustrated inFIG. 9, during the writing to a magnetic recording layer of the magnetic disk301by the electromagnetic transducer element22, laser light (waveguide light)63radiated from the laser diode60in the light source unit50initially propagates through the waveguide23. Next, the laser light (waveguide light)63that has propagated to the vicinity of the buffer portion40is coupled with the optical configuration of the waveguide23having a predetermined refractive index nWG, the buffer portion40having a predetermined refractive index nBF, and then the plasmon generator24made of a conductive material such as metal or the like, and the surface plasmon mode is induced at the projection part241of the plasmon generator24. That is, the laser light (waveguide light)63is coupled with the plasmon generator24in the surface plasmon mode. Actually, evanescent light is excited in the buffer portion40based on the optical interfacial condition between the waveguide23, which is the core, and the buffer portion40. Then, the surface plasmon mode is induced such that the evanescent light and fluctuation of charges excited at the metal surface (projection part241) of the plasmon generator24are coupled with each other, and the surface plasmon is excited. Note, more precisely, since the surface plasmon that is elementary excitation is coupled with electromagnetic wave in this system, surface plasmon•polariton is excited. However, hereinafter, the surface plasmon•polariton is referred to as surface plasmon for short. The excitation of the surface plasmon mode can be achieved by setting the refractive index nBFof the buffer portion40smaller than the refractive index nWGof the waveguide23(nBF<nWG) and by appropriately selecting the length LBFof the buffer portion40in the X axis direction, which is in other words the length of the coupling portion of the waveguide23and the plasmon generator24, and the thickness TBF(gap G between the waveguide23and the projection part241: preferably 15-40 nm and further preferably 25-30 nm) of the buffer portion40in the Z axis direction.

In the excited surface plasmon mode, the surface plasmon70is excited on the projection part241of the plasmon generator24to propagate on the projection part241along the direction of an arrow71. Since the projection part241does not contact the pole22c, the projection part241does not receive bad effects from the pole22ceven when adjustment for efficient excitation of the surface plasmon has not done. As a result, it becomes possible to intentionally propagate the surface plasmon on the projection part241.

As described above, by the surface plasmon70propagating on the projection part241in the direction of the arrow71, the surface plasmon70, which is in other words a electric field, is concentrated in the near-field light generating portion NFP on the near-field light generating end surface24athat reaches the head part end surface12aand that is an end of the projection part241. As a result, the near-field light72is generated from the near-field light generating portion NFP. The near-field light72is irradiated toward the magnetic recording layer of the magnetic disk301, reaches the surface of the magnetic disk301, and heats the portion of the magnetic recording layer of the magnetic disk301. Thereby, the anisotropy field (coercive force) of the portion is reduced to the value that allows the writing, and the writing is performed by the magnetic field that has been applied to the portion.

Herein, in the present embodiment, the distance MO (seeFIG. 5andFIG. 6) on the head part end surface12abetween the pole22cand the projection part241of the plasmon generator24(upper surface of the projection part) is set to be shorter in comparison with a conventional thermally-assisted magnetic recording head (10-40 nm). Generally, when the distance MO is shortened, light (surface plasmon) propagating through the projection part241of the plasmon generator24is more likely to be absorbed by the pole22c, and thereby there is a risk that the light intensity of the near-field light generated from the near-field light generating portion NFP may reduce. However, in the present embodiment, on the projection part opposing surface22c1of the pole22c, the light penetration suppression part26is provided, and therefore it becomes possible to suppress light (surface plasmon) from being absorbed by the pole22cand to generate near-field light with a light intensity sufficient to reduce the anisotropy field of the magnetic disk301. As a result, according to the thermally-assisted magnetic recording head1of the present embodiment, it enables a steep magnetization reversal between adjacent magnetic domains of the magnetic disk301, so that it becomes possible to satisfy the requirement of high recording density and high SN ratio.

Also, when the distance MO is short (10-40 nm), diffusion of near-field light onto the pole22cside, the near-field light being generated from the near-field light generating portion NFP of the plasmon generator24, is suppressed by the existence of the pole22c. Therefore, the spot diameter of near-field light irradiated to the magnetic disk301may be reduced. Furthermore, from the perspective of the head part end surface12aside, the provision of the nonmagnetic metal parts NM and NM on the both side of the pole22cin the track width direction enables to suppress near-field light from spreading in the track width direction, and as a result the spot diameter of near-field light irradiated to the magnetic disk301can be further reduced. The spot diameter of near-field light can be reduced as described above, and thereby it becomes possible to comply with even higher recording density.

Furthermore, due to the generation of the near-field light72, heating occurs in the vicinity of the near-field light generating portion NFP of the near-field light generating end surface24a; however, the heat dissipates into the plane part240of the plasmon generator24. As a result, this can contribute to suppress the excessive temperature increase in the plasmon generator24and to prevent an unnecessary projection of the near-field light generating end surface24aand a significant reduction in light usage efficiency of the plasmon generator24. Further, because the pole22cand the plasmon generator24are not contacted to each other, it is possible to suppress heat dissipation into the pole22cside and also to suppress the deterioration or the like of the pole22cdue to the heat dissipation into the pole22cside. Note, due to generation of the near-field light72, little heat is occasionally stored in the pole22c; however, when the nonmagnetic metal parts NM and NM contact the both side surfaces of the pole22cfrom the perspective of the head part end surface12aside, the heat can dissipate from the pole22cinto the nonmagnetic metal parts NM and NM, and therefore it is possible to further suppress deterioration of the pole22c, etc.

The thermally-assisted magnetic recording head having the above-described configuration can be manufactured as will be described below.

FIGS. 10A-10Jare perspective views mainly schematically illustrating steps of forming the plasmon generator24, the pole22c, and the waveguide23of the thermally-assisted magnetic recording head1according to the present embodiment.

Initially, a metal layer90with a predetermined thickness (for example, approximately 60 nm) made of Au or Au alloy, etc. is formed by using, for example, a sputtering method on the eighth insulating layer32hmade of Al2O3, SiO2, or the like (seeFIG. 10A). The metal layer90eventually becomes the plasmon generator24.

Next, a photoresist film PR1is formed so as to cover the metal layer90, and then patterning is performed. By using a remaining photoresist film PR1as a mask, etching is performed using a dry etching method such as ion milling or the like such that the thickness of the metal layer90in the portion on which the photoresist film PR1does not exist becomes a predetermined thickness (for example, approximately 30 nm) (seeFIG. 10B). By doing so, the plasmon generator24having the plane part240and the projection part241is formed.

Next, Al2O3, SiO2, or the like is refilled so as to cover portions above the plane part240of the plasmon generator24to form insulating layers91, and the remaining photoresist film PR1is peeled (seeFIG. 10C). Then, an insulating layer92formed of Al2O3, SiO2, or the like is formed on the upper surface of the projection part241and the insulating layers91by using, for example, a sputtering method (seeFIG. 10D). A portion of the insulating layer92eventually becomes a gap between the waveguide23and the plasmon generator24(projection part241), which is the buffer portion40. Because the thickness of the insulating layer92affects the coupling efficiency of the laser light (waveguide light)63at the projection part241of the plasmon generator24, it is required to control a film formation thickness of the insulating layer92to be an appropriate thickness.

Next, after forming a TaOxlayer93on the insulating layer92and forming a photoresist film PR2on the TaOxlayer93, patterning is performed (seeFIG. 10E). The TaOxlayer93positioned directly below the photoresist film PR2that remains as described above eventually becomes the waveguide23.

Next, by using the remaining photoresist film PR2as a mask, etching is performed on the portions of the TaOxlayer93on which the photoresist film PR2does not exist using a dry etching method such as ion milling, or the like. Then, the remaining photoresist film PR2is peeled, insulating layers94formed of Al2O3, SiO2, or the like are formed in the portions where the TaOxlayer93has been etched using, for example, a sputtering method or the like, and planarization is performed using a polishing method such as chemical mechanical polishing (CMP) or the like (seeFIG. 10F).

Next, after forming a photoresist film PR3on the remaining TaOxlayer93and the remaining insulating layers94, patterning is performed (seeFIG. 10G). Next, etching is performed on a portion of the TaOxlayer93by a dry etching method such as ion milling or the like, a metal thin film95made of Al or the like is formed on the exposed insulating layer92by sputtering or the like, and then the remaining photoresist film PR3is peeled (seeFIG. 10H). By doing so, it is possible to form the waveguide23and the light penetration suppression part26positioned on the back side of the pole22cin the X axis direction (height direction).

Next, a magnetic material such as FeCo or the like is plated on the light penetration suppression part26, planarization is performed by using a polishing method such as chemical mechanical polishing (CMP) or the like, and thereby the pole22cis formed. Next, patterning is performed after forming a photoresist film on the pole22c, the waveguide23, and the insulating layers94, etching is performed on portions of the insulating layers94, the insulating layer92, and the insulating layers91by using a dry etching method such as ion milling, the plane part240of the plasmon generator24and the both side surfaces of the pole22cfrom the perspective of the head part end surface12aside are exposed, a nonmagnetic metal96such as Cu or the like is plated on the exposed plane part240, and planarization is performed by using a polishing method such as chemical mechanical polishing (CMP) or the like (seeFIG. 10I). By doing so, it is possible to form the nonmagnetic metal parts NM and NM contacting the both side surfaces of the pole22cin the Y axis direction from the perspective of the head part end surface12aside and the plane part240of the plasmon generator24.

Lastly, a magnetic material such as FeCo or the like is plated in a manner of covering the pole22cto form the upper yoke layer22d, the protective layer31formed of Al2O3(alumina) or SiO2is formed by using, for example, a sputtering method or the like, and then planarization is performed by using a polishing method such as chemical mechanical polishing (CMP) or the like (seeFIG. 10J). As described above, it is possible to manufacture the head part12in the present embodiment.

The above-described embodiment is provided for a clear understanding of the present invention, and is not provided to limit the present invention. Therefore, each of the elements disclosed in the above-described embodiment also includes any design changes and equivalents thereof that belong to the technical scope of the present invention.

Also, in the thermally-assisted magnetic recording head1according to the above-described embodiment, the shape of the projection part241is rectangular when the projection part241projected from the plane part240of the plasmon generator24is viewed from the head part end surface12aside; however, the present invention is not limited to such form. The shape of the projection part241when the projection part241is viewed from the head part end surface12aside may be substantially trapezoidal or substantially invertedly trapezoidal; the shape of an angle at the intersection of the side (side in the Z axis direction) of the projection part241when the projection part241is viewed from the head part end surface12aside and the plane part240may be curved.

In the thermally-assisted magnetic recording head1according to the above-described embodiment, the nonmagnetic metal parts NM and NM are formed upright on the plane part240of the plasmon generator24; however, the present invention is not limited to such form. The nonmagnetic metal parts NM and NM need only contact at least the both side surfaces of the pole22cfrom the perspective of the head part end surface12aside, and the plane part240and the nonmagnetic metal parts NM and NM may be separated.

EXAMPLES

Hereinafter, further detailed description of the present invention will be given showing experimental examples; however, the present invention is not particularly limited to the experimental examples, which will be described below.

Experimental Example 1

By using the thermally-assisted magnetic recording head1having the configuration illustrated inFIGS. 4-7, regarding the relation between the near-field light peak intensity and the distance MO between the pole22cand the projection part241of the plasmon generator24, simulation analysis experiment was performed (example 1).

The simulation analysis experiment was performed using a finite-difference time-domain method (FDTD method) of three dimensions, which is an electromagnetic field analysis.

As the thermally-assisted magnetic recording head1in the example 1, a model was adopted. In the model, the pole22cwas formed of a FeCo alloy, the waveguide23was formed of Ta2O5(refractive index nWG=2.15), the protective layer31and the buffer portion40(the ninth insulating layer32i) were formed of SiO2(refractive index n=1.46), the plasmon generator24was formed of Au, the nonmagnetic metal part NM was formed of Cu, and the light penetration suppression part26was formed of Al.

In the model, a projection height TPGCof the projection part241of the plasmon generator24was set at 30 nm; a height TPGfrom the lower surface of the plane part240to the upper surface of the projection part241was set at 130 nm; a width WPGCof the projection part241in the Y axis direction on the near-field light generating end surface24awas set at 30 nm; a length HPGof the plasmon generator24in the X axis direction was set at 1.2 μm; the gap G (thickness TBFof the buffer portion40in the Z axis direction) between the waveguide23and the projection part241was set at 25 nm; a length of the nonmagnetic metal part NM in the X axis direction was set at 5 μm; and the wavelength of laser light (waveguide light) was set at 797 nm. Furthermore, the winding number of the writing coil22bwas set at 3; input current value was set at 40 mA.

Then, while the distance MO between the pole22con the head part end surface12aand the projection part241(upper surface of the projection part) of the plasmon generator24was varied in the range of 5-45 nm, the relation between the near-field light peak intensity and the distance MO was calculated by simulation analysis.

With respect to the thermally-assisted magnetic recording head1that has the same configuration as the example 1 other than that the nonmagnetic metal parts NM and NM were not provided in, regarding the relation between the near-field light peak intensity and the distance MO (5-45 nm), simulation analysis experiment was performed in the same way as the example 1 (example 2).

Comparative Example 1

As illustrated in the plan view from the perspective of the head part end surface side inFIG. 11, with respect to a conventional thermally-assisted magnetic recording head1000provided with a waveguide2300, a plasmon generator2400provided above the waveguide2300with an insulating layer (buffer portion)4000intervened between the waveguide2300and the plasmon generator2400, and a pole2200provided on the plasmon generator2400, regarding the relation between the near-field light peak intensity and the distance MO, simulation analysis experiment was performed in the same way as the example 1 (comparative example 1).

In the thermally-assisted magnetic recording head1000of the comparative example 1, the plasmon generator2400has a substantially V-shaped part2400athat has a substantial V-shape from the perspective of the head part end surface side, extended parts2400bthat continue to upper end parts of the substantially V-shaped part2400aand that extend in the Y axis direction, and a propagation edge2410that is positioned in an apex of the substantially V-shaped part2400aand that elongates in the X axis direction. Inside the substantially V-shaped part2400aof the plasmon generator2400, one part of the pole2200is embedded.

Note, as the thermally-assisted magnetic recording head1000of the comparative example 1, a model was adopted. In the model, the pole2200was formed of a FeCo alloy, the waveguide2300was formed of Ta2O5(refractive index nWG=2.15), the buffer portion4000was formed of SiO2(refractive index n=1.46), and the plasmon generator24was formed of Au.

In the model, an angle that forms an apex of the pole2200embeded inside the substantially V-shaped part2400aof the plasmon generator2400was set at 90 degree. Also, the gap G (thickness of the buffer portion4000in the Z axis direction) between the waveguide2300and the propagation edge2410was set at 25 nm, and the wavelength of laser light (waveguide light) was set at 797 nm. Furthermore, the winding number of the writing coil22bwas set at 3, and input current value was set at 40 mA.

Then, while the distance MO between the propagation edge2410on the head part end surface and the apex of the pole2200embedded inside the substantially V-shaped part2400awas varied in the range of 20-50 nm, the relation between the near-field light peak intensity and the distance MO was calculated by simulation analysis in the same way as the example 1.

FIG. 12illustrates the simulation analysis experiment results of the example 1, the example 2, and the comparative example 1.FIG. 12is a graph illustrating the simulation analysis experiment results. Note, in the graph illustrated inFIG. 12, the Y axis is indicated using relative values when the near-field light peak intensity when the distance MO in the thermally-assisted magnetic recording head1000of the comparative example 1 is 35 nm is defined as 100%.

As is clear from the graph inFIG. 12, in the thermally-assisted magnetic recording head1of the example 1, when the distance MO between the pole22cand the projection part241of the plasmon generator24was set to be 10-40 nm, an increasing effect of the near-field light peak intensity was recognized.

Also, in the thermally-assisted magnetic recording head1of the example 2, when the distance MO between the pole22cand the projection part241of the plasmon generator24was set to be 16-36 nm, an increasing effect of the near-field light peak intensity was recognized.

Further, from the simulation analysis results of the above-described example 1 and example 2, by providing the nonmagnetic metal parts NM and NM on the both side surfaces of the pole22cin a contacting manner from the perspective of the head part end surface12aside, it was presumptively recognized that deffusion of near-field light in the track width direction can be suppressed and the spot diameter of near-field light can be reduced.

Experimental Example 2

In a model used, for the example 1 and the example 2, the distance MO between the pole22cand the projection part241of the plasmon generator24was set at 25 nm, and for the comparative example 1, the distance MO between the propagation edge2410on the head part end surface and the apex of the pole2200embedded inside the substantially V-shaped part2400awas set at 35 nm. With the model, spot diameters (in a cross-track direction (CT) and in a down-track direction (DT)) of near-field light were calculated by simulation analysis. The simulation analysis experiment was performed by using a finite-difference time-domain method (FDTD method) of three dimensions, which is an electromagnetic field analysis. The results are shown in Table 1. Note, in order that the peak intensities of near-field light in all of the thermally-assisted magnetic recording heads in the example 1, the example 2, and the comparative example 1 are almost the same, the distance MO in the example 1 and the example 2 was set at 25 nm, and in contrast the distance MO in the comparative example 1 was set at 35 nm.

As is clear from Table 1, it was confirmed that, in the thermally-assisted magnetic recording heads1of the example 1 and the example 2 compared to the thermally-assisted magnetic recording head1000, it was possible to reduce a spot diameter of near-field light. Also, it was confirmed that, in the thermally-assisted magnetic recording head1of the example 1 in which the nonmagnetic metal parts NM and NM are provided so as to contact the both side surfaces of the pole22cwhen viewed from the head part end surface12aside, it is possible to reduce a spot diameter of near-field light due to the function of the nonmagnetic metal parts NM and NM.

Experimental Example 3

By using the thermally-assisted magnetic recording head1of the example 1, regarding the relation between SNR and the thickness TLPIof the light penetration suppression part26and the relation between the spot diameter of near field light and the thickness TLPIof the light penetration suppression part26while thickness TLPIof the light penetration suppression part26was varied in the range of 0-15 nm, simulation analysis experiment was performed in the same way as the example 1. In the simulation analysis experiment, in the case where the thickness TLPIof the light penetration suppression part26is 0 nm (light penetration suppression part26is not provided), the distance MO between the pole22cand the projection part241(upper surface of the projection part) of the plasmon generator24was set at 25 nm. Also, when the thickness TLPIof the light penetration suppression part26was varied, the pole22cwas slided upward (in the trailing side) by the distance of the thickness TLPIand arranged at the position. In other words, the distance between the projection part241(upper surface of the projection part) of the plasmon generator24and the light penetration suppression part26was set to be constant at 25 nm.

The result is shown in the graph ofFIG. 13. Note, inFIG. 13, the Y-axis is indicated using relative values when SNR and spot diameter of the thermally-assisted magnetic recording head in which the thickness TLPIof the light penetration suppression part26is 0 nm, that is, the light penetration suppression part26is not provided, was defined as 100%

As illustrated inFIG. 13, it was confirmed that in the thermally-assisted magnetic recording head1of the example 1, regarding SNR, the thickness TLPIof the light penetration suppression part26is preferably 0.5-6.25 (SNR≧105%), further preferably 1.25-5.5 nm (SNR≧115%). Also, regarding the spot diameter of near-field light, it was confirmed that the spot diameter was reduced as the thickness TLPIof the light penetration suppression part26was thickened.