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

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 that propagates light to excite surface plasmon; and a plasmon generator that is provided between the pole and the waveguide and that generates near-field light from a near-field light generating end surface that forms a part of the air bearing surface by coupling with the light in a surface plasmon mode. The plasmon generator includes a flat plate part and a projection part that projects from the flat plate part to the waveguide side and is provided closer to a trailing side than the pole is.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a head for a thermally assisted magnetic recording that records data by emitting near-field (NF) light on a magnetic recording medium and by decreasing an anisotropic magnetic field of the magnetic recording medium and to a head gimbal assembly and a magnetic recording device that uses such head.

2. Description of the Related Art

In the field of magnetic recording using a head and a medium, further improvements have been demanded in performance of thin film magnetic heads and magnetic recording media in view of an increase in recording density of magnetic disk devices. For the thin film magnetic heads, composite type thin film magnetic heads configured from lamination of a reading magnetoresistive (MR) element and a writing electromagnetic conversion element are being widely used.

The magnetic recording medium is a non-continuous medium, in which magnetic microparticles are aggregated. Each magnetic microparticle has a single magnetic domain. In this magnetic recording medium, a single recording bit is configured by a plurality of magnetic microparticles. Therefore, to increase magnetic density, the size of the magnetic microparticles must be reduced, and asperity at a border of adjacent recording bits needs to be minimized. However, if the size of the magnetic microparticles is reduced, there is a problem that thermal stability for magnetization of the magnetic microparticles is lowered as the volume of the magnetic microparticles is reduced.

To address this problem, increasing magnetic anisotropic energy Ku of magnetic microparticles may be considered. However, this increase in Ku causes an increase in anisotropic magnetic field (coercive force) of the magnetic recording medium. On the other hand, the upper limit of the writing magnetic field intensity for the thin film magnetic head is determined substantially by saturation magnetic flux density of a soft magnetic material forming a magnetic core in the head. As a result, when the anisotropic magnetic field of the magnetic recording medium exceeds an acceptable value determined from the upper value of the writing magnetic field intensity, writing becomes impossible. Currently, as a method to solve such a problem of thermal stability, a so-called thermally assisted magnetic recording method has been proposed, which, using a magnetic recording medium formed by a magnetic material with large Ku, performs the writing by heating the magnetic recording medium immediately before applying the writing magnetic field to reduce the anisotropic magnetic field.

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

A magnetic recording head provided with a conventional plasmon generator has a configuration in which a main pole is provided on a trailing side of a near-field light generating portion of the plasmon generator and in which a waveguide that propagates light is provided so as to oppose the plasmon generator. This plasmon generator excites surface plasmon by coupling with the light that propagates through the waveguide in surface plasmon mode and generates near-field light at the near-field light generating portion as a result of propagation by this surface plasmon propagating through the plasmon generator. Furthermore, a magnetic recording medium is heated by the near-field light generated at the near-field light generating portion of the plasmon generator, an isotropic magnetic field of the magnetic recording medium is reduced, and thereby information is written. However, with a magnetic recording head having this configuration, after the temperature rises due to heating, the magnetic field is also applied to the magnetic recording medium during the cooling process. Accordingly, after the application of the magnetic field for recording is completed, the magnetic field is further applied even onto the magnetic microparticles where the magnetization has not yet stabilized. Therefore, there is a problem that sufficient signal-to-noise ratio (S/N ratio) cannot be obtained at high recording density.

Therefore, in order to achieve high recording density and obtain a sufficient S/N ratio, a configuration, in which a magnetic field is applied prior to heating the magnetic recording medium, is conceivable. Or in other words, that is a configuration where the plasmon generator of a conventional magnetic recording head is provided on the trailing side of the main pole. A magnetic recording head as described in Japanese Patent Publication No. 2010-244670 has been proposed as a magnetic recording head with this configuration. With this magnetic recording head, it is thought that almost no magnetic field is applied to the magnetic recording medium during the cooling process, therefore, rapid magnetization reversal is possible in the adjacent magnetic domains on the magnetic recording medium, and that the requirements for high recording density and sufficient S/N ratio can be satisfied. However, the light spot diameter of the near-field light irradiated on the magnetic recording medium by the near-field light generating portion is currently being required to be even smaller because of demand for even higher recording density in recent years.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a thermally-assisted magnetic recording head that further reduces a light spot diameter of near-field light irradiated onto a magnetic recording medium from a near-field light generating portion of a plasmon generator, and to provide a head gimbal assembly and a magnetic recording device that uses this head.

In order to achieve the object, the present invention provides a thermally-assisted magnetic recording head including: 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 that propagates light to excite surface plasmon; and a plasmon generator that is provided between the pole and the waveguide and that generates near-field light from a near-field light generating end surface that forms a part of the air bearing surface by coupling with the light in a surface plasmon mode. The plasmon generator includes a flat plate part which at least partly contacts the pole and a projection part (convex part) that projects from the flat plate part to the waveguide side and is provided closer to a trailing side than the pole is (first invention).

With the present invention, the near-field light generating end surface refers to an end surface that configures a portion of the air bearing surface in a plasmon generator.

In the first invention, it is preferred that the projection part is contiguous from the near-field light generating end surface along a light propagating direction of the waveguide (second invention). It is preferred that a protrusion height of the projection part is from 20 to 30 nm (third invention). It is preferred that a length of the plasmon generator in a light propagation direction of the waveguide is no less than a length of the pole in the light propagation direction (fourth invention), further that the length is from 1 to 14 μm (fifth invention). It is preferred that a width of the pole as viewed from the air bearing surface is from 0.2 to 0.3 μm, in a direction approximately orthogonal to a direction of travel of the magnetic recording medium (sixth invention).

Further, in the first invention, it is preferred that a shape of a surface of the projection part that opposes the waveguide is approximately a trapezoidal shape with a short side located on the air bearing surface side, a long side approximately parallel to the short side, and two oblique sides (seventh invention). In the seventh invention, an angle formed by the oblique sides with regards to a direction perpendicular to the air bearing surface is less than 10° (eighth invention).

In the first invention, it is preferred that a length from a lower end of the flat plate part to an upper end of the projection part is from 45 to 75 nm, as viewed from the air bearing surface side such that the waveguide is located closer to the trailing side than the plasmon generator (ninth invention). It is preferred that a gap between a lower end of the waveguide and an upper end of the projection part is from 15 to 40 nm, as viewed from the air bearing surface side such that the waveguide is located closer to the trailing side than the plasmon generator (tenth invention).

Further, the present invention provides a head gimbal assembly, including: the thermally-assisted magnetic recording head with respect to the above first invention; and a suspension that supports the thermally-assisted magnetic recording head (eleventh invention).

Furthermore, the present invention provides a magnetic recording device, including: a magnetic recording medium; the thermally-assisted magnetic recording head with respect to the above invention (first invention); and a positioning device that supports the thermally-assisted magnetic recording head and determines a position with regards to the magnetic recording medium (twelfth invention).

The present invention provides a thermally-assisted magnetic recording head that further reduces the light spot diameter of the near-field light irradiated onto the magnetic recording medium from the near-field light generating portion of the plasmon generator, and provides a head gimbal assembly and a magnetic recording device that uses this recording head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining embodiments 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 embodiments of the present invention, from a reference layer or element, the substrate side is called “downward (lower direction),” and the opposite side is called “upward (upper direction).” In addition, in the magnetic recording head according to embodiments of the present invention, some of the drawings provide “X, Y and Z axis directions” if necessary. Here, the Z axis direction is 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 an embodiment of the present invention is explained with reference to the drawings.

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

As shown inFIG. 1, a magnetic disk device, which is a magnetic recording device according to the present embodiment includes a plurality of magnetic disks301that rotate about a rotational axis of a spindle motor302, an assembly carriage device310provided with a plurality of drive arms311, a head gimbal assembly (HGA)312attached to a front end of each drive arm311and having a thermally assisted magnetic recording head1, which is a thin film magnetic head, according to the present embodiment, and a control circuit330that controls writing and reading operations of the thermally assisted magnetic recording head1according to the present embodiment and that controls a light emission operation of a laser diode, which is a light source that generates laser light for the later-discussed thermally assisted magnetic recording.

In the present embodiment, the magnetic disks301are for perpendicular magnetic recording and have a configuration, in which a soft magnetic under layer, an intermediate layer and a magnetic recording layer (perpendicularly magnetized layer) are sequentially laminated on a disk substrate.

The assembly carriage device310is a device for positioning the thermally assisted magnetic recording head1on a track, which is formed on the magnetic disk301and on which recording bits are 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) about the pivot bearing shaft313.

The configuration of the magnetic disk device of the present embodiment is not limited to the above-described configuration but may include only a single set of the magnetic disk301, the drive arm311, the HGA312and the thermally assisted magnetic recording head1.

In the HGA312shown inFIG. 2, a suspension320includes a load beam321, a flexure322that is fixed to the load beam321and has elasticity, and a base plate323provided at a base of the load beam321. In addition, a wiring member324formed from a lead conductor and a connection pads electrically connected to both sides of the lead conductor are provided on the flexure322. The thermally assisted magnetic recording head1according to the present embodiment opposes a surface of the respective magnetic disk301with a predetermined space (flying height) and is fixed to the flexure322at the front end of the suspension320. Further, an end of the wiring member324is electrically connected to a terminal electrode of the thermally assisted magnetic recording head1according to the present embodiment. The configuration of the suspension320in the present embodiment is also not limited to the above-described configuration but may include a head driving IC chip (not shown) attached to the middle of the suspension320.

As shown inFIG. 3, the thermally assisted magnetic recording head1according to the present embodiment includes a slider10and a light source unit50. The slider10is formed from ALTIC (Al2O3—TiC) or the like and includes a slider substrate11having an air bearing surface (ABS)11a, which is a medium opposing surface, processed to obtain an appropriate flying height, and a head part12formed on an element formation surface11bthat is perpendicular to the ABS11a.

Furthermore, the light source unit50is formed from ALTIC (Al2O3—TiC) or the like and includes a unit substrate51having a joining surface51a, and a laser diode60, which is a light source provided on the light source installation surface51bthat is perpendicular to the joining surface51a.

The slider10and the light source unit50are joined with each other by bonding a back surface11cof the slider substrate11and the joining surface51aof the unit substrate51. The back surface11cof the slider substrate11means an end surface opposite from the ABS11aof the slider substrate11. The thermally assisted magnetic recording head1according to the present embodiment may have a configuration, in which the laser diode60is directly attached to the slider10without the light source unit50.

The head part12formed on the element formation surface11bof the slider substrate11includes a head element20that has an MR element21for reading out data from the magnetic disk301and an electromagnetic conversion element22for writing data on the magnetic disk301, a waveguide23for guiding the laser light from the laser diode60provided on the light source unit50to the side of the medium opposing surface, a plasmon generator24that forms a near-field light generating optical system with the waveguide23, a passivation layer31formed on the element formation surface11bto cover the MR element21, the electromagnetic conversion element22, the waveguide23and the plasmon generator24, a pair of first terminal electrodes25athat are exposed from the upper surface of the passivation layer31and that are electrically connected to the MR element21, and a pair of second terminal electrodes25bthat are exposed from the upper surface of the passivation layer31and that are electrically connected to the electromagnetic conversion element22. The first and second terminal electrodes25aand25bare electrically connected to the connection pad of the wiring member324provided to the flexure322(FIG. 2).

Ends of the MR element21, the electromagnetic conversion element22and the plasmon generator24reach a head part end surface12a, which is the medium opposing surface of the head part12. The head part end surface12aand the ABS11aform the entire medium opposing surface for the thermally assisted magnetic recording head1according to the present embodiment.

During the actual writing and reading of data, the thermally assisted magnetic recording head1hydro-dynamically flies on the surface of the rotating magnetic disk301with a predetermined flying height. At this time, the end surfaces of the MR element21and the electromagnetic conversion element22oppose the surface of the magnetic recording layer of the magnetic disk301with an appropriate magnetic spacing. In this state, the MR element21reads data by sensing a data signal magnetic field from the magnetic recording layer, and the electromagnetic conversion element22writes data by applying the data signal magnetic field to the magnetic recording layer.

At the time of writing data, the laser light that propagates from the laser diode60of the light source unit50through the waveguide23is coupled with the plasmon generator24in a surface plasmon mode and excites a surface plasmon at the plasmon generator24. This surface plasmon propagates along the later-discussed propagation edge provided at the plasmon generator24towards the head part end surface12aso that the near-field light is generated at the end of the plasmon generator24on the side of the head part end surface12a. This near-field light heats a part of the magnetic recording layer of the magnetic disk301as it reaches the surface of the magnetic disk301. As a result, anisotropic magnetic field (coercive force) at that part decreases to a value at which the writing becomes possible. Thermally assisted magnetic recording can be achieved by applying a writing magnetic field to the part where the anisotropic magnetic field has decreased.

FIG. 4is a cross-sectional view from an A-A line (XZ plane) inFIG. 3that schematically shows a configuration the thermally assisted magnetic recording head1according to the present embodiment.

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

The lower shield layer21band the upper shield layer21care magnetic layers with a thickness of approximately 0.5-3 μm formed by a frame plating method or a spattering method, for example, and are formed by a soft magnetic material, such as NiFe (Permalloy), FeSiAl (Sendust), CoFeNi, CoFe, FeN, FeZrN, CoZrTaCr or the like, or a multilayer formed by these materials.

The MR multilayer21bis a magnetically sensitive part that senses the signal magnetic field using the MR effect and may be any of a current-in-plane giant magnetoresistive (CIP-GMR) multilayer that uses a current-in-plane giant magnetoresistive effect, a current-perpendicular-to-plane giant magnetoresistive (CPP-GMR) multilayer that uses a current-perpendicular-to-plane giant magnetoresistive effect, and a tunnel-magnetoresistive (TMR) multilayer that uses a tunnel magnetoresistive effect. If the MR multilayer21bis a CPP-GMR multilayer or a TMR multilayer, the lower shield layer21aand the upper shield layer21cfunction as electrodes also. On the other hand, if the MR multilayer21bis a CIP-GMR multilayer, insulation layers are provided between the MR multilayer21band each of the lower shield layer21aand the upper shield layer21c. Moreover, an MR lead layer that is electrically connected to the MR multilayer21bis provided.

If the MR multilayer21bis a TMR multilayer, the MR multilayer21bhas a configuration in which the following are sequentially laminated: an antiferromagnetic layer of IrMn, PtMn, NiMn, RuRhMn or the like having a thickness of approximately 5-15 nm; a magnetization pinned layer that has a configuration in which two ferromagnetic layers of CoFe or the like sandwich a nonmagnetic metal layer of Ru or the like and in which a magnetization direction is pinned by the antiferromagnetic layer; a tunnel barrier layer of a nonmagnetic dielectric material in which a metal film of Al, AlCu or the like having a thickness of 0.5-1 nm is oxidized by oxygen introduced in a vacuum device or by natural oxidation; and a magnetization free layer that is formed by a layer of CoFe or the like having a thickness of approximately 1 nm and a layer of NiFe or the like having a thickness of approximately 3-4 nm, which are ferromagnetic materials, and that achieves tunnel exchange coupling with the magnetization pinned layer through the tunnel barrier layer.

The head part12in this embodiment includes a third insulation layer32cprovided on the upper part shield layer21c, an inter-element shield layer33provided on the third insulation layer32c, and a fourth insulation layer32dprovided on the inter-element shield layer33. The inter-element shield layer33may be formed from a soft magnetic material, and has a function that shields the MR element21from the magnetic field generated by the electromagnetic transducer element22provided on the fourth insulation layer32d. The third insulation layer32cand the inter-element shield layer33may be omitted.

The electromagnetic transducer element22is for perpendicular magnetic recording, and includes a lower part yoke layer22aprovided on the fourth insulation layer32d, a linking layer22bprovided on the lower part yoke layer22ain a position separated in the X-axis direction from the head part end surface12a, an upper part yoke layer22cprovided on the linking layer22b, a writing coil22dwith a spiral structure wound around the linking layer22bso as to pass through at least the lower part yoke layer22aand the upper part yoke layer22ceach turn, and a pole22eprovided on the upper part yoke layer22cthat reaches the head part end surface12aso as to form a portion of the head part end surface12a.

The head part12in the present embodiment includes a fifth insulation layer32eprovided in the area around the lower part yoke layer22aon the fourth insulation layer32d, a sixth insulation layer32fprovided on the lower part yoke layer22aand the fifth insulation layer32e, a seventh insulation layer32gprovided in the area around the linking layer22bas well as between windings of the writing coil22dand surrounding area thereof, an eighth insulation layer32hprovided on the writing coil22dand the seventh insulation layer32g, a ninth insulation layer32iprovided in the area around the upper part yoke layer22con the eighth insulation layer32h, and a 10th insulation layer32jprovided in the area around the pole22eon the upper part yoke layer22cand the ninth insulation layer32i.

In the head part12in the present embodiment, the lower part yoke layer22a, linking layer22b, upper part yoke layer22c, and pole22eform a magnetic guide path that allows the magnetic flux corresponding to the magnetic field generated by the writing coil22dto pass through, and guides the magnetic flux to the magnetic recording layer (perpendicular magnetization layer) of the magnetic disk301. The furthest trailing side of the end surface220of the pole22ethat forms a part of the head part end surface12ais the point that generates the writing magnetic field.

The pole22eis preferably formed from a soft magnetic material having a higher saturation magnetic flux density than the upper part yoke layer22c, and is formed, for example, from a soft magnetic material, such as FeNi, FeCo, FeCoNi, FeN, FeZrN or the like, which are ferroalloy materials having Fe as a main component. The thickness in the Z direction of the pole22ecan be set from 0.1 to 0.8 μm.

Furthermore, the width in the Y direction of the pole22eis preferably from 0.2 to 0.3 μm. If the width in the Y direction of the pole22eis within the aforementioned 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.

The end surface on the head part end surface12aside of the upper part yoke layer22cdoes not extend to the head part end surface12a, and is positioned at a location recessed from the head part end surface12aby a predetermined distance toward the head part back end surface12bside in the X direction. Thereby, magnetic flux can be concentrated at the pole22e, and the intensity of the magnetic field generated from the pole22ecan be strengthened.

The writing coil22dis formed from a conductive material, such as Cu (copper) or the like. The writing coil22dis a single layer in the present embodiment, but can also be two or more layers, and can be a helical coil arranged such that the upper part yoke layer22cis interposed therebetween. Furthermore, the number of windings of the writing coil22dis not particularly restricted, and can be set from 2 to 7 turns, for example.

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

The waveguide23and the plasmon generator24are provided above the pole22eand form an optical system for generating near-field light in the head part12. The waveguide23is in parallel with the element formation surface11band extends from a rear end surface23athat forms a part of a head part rear end surface12bto the end surface23bthat forms a part of the head part end surface12a. In addition, a part of the lower surface (side surface) of the waveguide23and a part of the upper surface of the plasmon generator24(including the projection part241) oppose each other with a predetermined gap. A part that is sandwiched between those parts forms a buffer portion40that has a lower refractive index than the refractive index of the waveguide23.

The buffer portion40functions to couple the laser light that propagates through the waveguide23to the plasmon generator24in the surface plasmon mode. The buffer portion40may be a part of a tenth insulation layer32jthat is a part of the passivation layer31or may be another layer provided separately from the tenth insulation layer32j.

The plasmon generator24is provided at a position between the waveguide23and the pole22e. With the thermally-assisted magnetic recording head1according to the present embodiment, the plasmon generator24is provided closer to the trailing side than the pole22e. The specific structures of the pole22e, waveguide23, and plasmon generator24are described later.

As shown inFIG. 4, the light source unit50includes the unit substrate51, the laser diode60provided on the light source installation surface51bof the unit substrate51, a first drive terminal electrode61electrically connected to an electrode that forms a lower surface60aof the laser diode60, and a second drive terminal electrode62electrically connected to an electrode that forms an upper surface60bof the laser diode60. The first and second drive terminal electrodes61and62are electrically connected to the connection pads of the wiring member324provided at the flexure322(FIG. 2). When a predetermined voltage is applied to the laser diode60via the first and second drive terminal electrodes61and62, laser light is emitted from an emission center located on an emission surface60cof the laser diode60. In the head structure shown inFIG. 4, an oscillation direction of the electric field of laser light that the laser diode60generates is preferably perpendicular (Z axis direction) to a lamination layer plane of an active layer60d. That is, it is preferable that the laser light which the laser diode60generates is a TM-mode polarized light. As a result, the laser light that propagates through the waveguide23can be coupled to the plasmon generator24in the surface plasmon mode through the buffer portion40.

For the laser diode60, InP-type, GaAs-type, and GaN-type diodes etc. may be used that are generally used for communication, optical disk storage, material analysis or the like. The wavelength λLfor the emitted laser light may be in a range of 375 nm-1.7 μm, for example.

More specifically, an InGaAsP/InP4 quaternary laser diode, of which the available wavelength region is considered to be 1.2-1.67 μm, for example, may be used. The laser diode60has a multilayer structure that includes the upper electrode60e, the active layer60dand the lower electrode60f. Reflection layers for exciting the oscillation by total reflection are formed on cleavage surfaces of this multilayer structure. In a reflection layer60g, an opening is provided at a position of the active layer60dthat includes the emission center60h. A thickness TLAof the laser diode60is approximately 60-200 μm, for example.

A power source in the magnetic disk device may be used for driving the laser diode60. Magnetic disk devices normally have a power source of approximately 2 V, for example, which has a sufficient voltage for operating the laser oscillation. In addition, power consumption of the laser diode60is approximately several tens of mW, for example, which can be sufficiently covered by the power source in the magnetic disk device. By applying a predetermined voltage by such a power source between the first drive terminal electrode61that is electrically connected to the lower electrode60fand the second drive terminal electrode62that is electrically connected to the upper electrode60e, and by oscillating the laser diode60, the laser light is emitted from the opening that includes the emission center60hin the reflection layer60g. The laser diode60and the first and second drive terminal electrodes61and62are not limited to the above-discussed embodiment. For example, the electrodes may be turned upside down in the laser diode60, and the upper electrode60emay be bonded to the light source installation surface51bof the unit substrate51. Furthermore, a laser diode may be provided on the element formation surface11bof the thermally assisted magnetic recording head1, and such a laser diode and the waveguide23may be optically connected. Moreover, an emission center of a laser diode provided in the magnetic disk device and the rear end surface23aof the waveguide23may be connected by an optical fiber or the like, for example, without providing the laser diode60in the thermally assisted magnetic recording head1.

The sizes of the slider10and the light source unit50may be arbitrary. For example, the slider10may be a femto slider, which has 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 light source unit50may be a size slightly smaller than the slider, which may have a width of 425 μm in the track width direction, a length of 300 μm and a thickness of 300 μm.

By connecting the above-described light source unit50and slider10, the thermally assisted magnetic recording head1is configured. For this connection, the contact surface51aof the unit substrate51and the rear surface11cof the slider substrate11are in contact. At this time, the unit substrate51and the slider substrate11are positioned so that the laser light generated from the laser diode60enters the rear end surface23aof the waveguide23that is opposite from the ABS11a.

FIG. 5Ais a perspective view schematically illustrating a configuration of the waveguide23, the plasmon generator24and the pole22efor the thermally assisted magnetic recording head1according to the present embodiment.FIG. 5Bis a perspective view schematically illustrating a configuration where the waveguide23has been removed from the thermally-assisted magnetic recording head illustrated inFIG. 5A. InFIGS. 5A and 5B, the head part end surface12athat includes positions from which the writing magnetic field and the near-field light are irradiated to the magnetic recording medium is positioned on the left side of the drawing.

As shown inFIG. 5A, the thermally assisted magnetic recording head1according to the present embodiment includes the waveguide23for propagating the laser light63for generating the near-field light, and the plasmon generator24having the projection part241that propagates the surface plasmon generated by the laser light (waveguide light)63.

The plasmon generator24includes the near-field light generating end surface24athat extends to the head part end surface12a(seeFIG. 7). In addition, the part sandwiched by a part of the side surface of the waveguide23and a part of the upper surface (side surface) of the plasmon generator24including the projection part241form the buffer portion40. That is, the projection part241is surrounded by the buffer portion40. This buffer portion40couples the laser light (waveguide light)63to the plasmon generator24in the surface plasmon mode. In addition, the projection part241propagates the surface plasmon excited by the laser light (waveguide light)63to the near-field light generating end surface24a.

The side surfaces of the waveguide23include end surfaces, excluding the end surface23bthat forms a part of the head side end surface12aand the rear end surface23aopposite from the end surface23b. The side surfaces of the waveguide23totally reflect the laser light (waveguide light)63that propagates in the waveguide23, which corresponds to a core. In the present embodiment, the side surface23cof the waveguide23, part of which contacts the buffer portion40, is the lower surface of the waveguide23.

More specifically, the laser light (waveguide light)63that has advanced to the vicinity of the buffer portion40induces the surface plasmon mode at the projection part241of the plasmon generator24as it is coupled to the optical structure formed by 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 metal. That is, the laser light (waveguide light)63is coupled to the plasmon generator24in the surface plasmon mode. This induction of the surface plasmon mode is achieved by setting the refractive index nBFof the buffer portion40to be smaller than the refractive index nWGof the waveguide23(nBF<nWG). Actually, evanescent light is excited in the buffer portion40based on the condition of the optical interface between the waveguide23, which is the core, and the buffer portion40. Then, the surface plasmon mode is induced as the evanescent light and a fluctuation of charges excited at the surface (projection part241) of the plasmon generator24are coupled, and the surface plasmon70is excited (seeFIG. 8). Here, the surface plasmon70is easily excited at the projection part241, because the projection part241is located closest to the waveguide and because the electric field is easily focused as the projection part241has extremely small width in the Y axis direction.

The gap G between the lower surface of the waveguide23(surface opposing the plasmon generator24) and the upper surface of the projection part241of the plasmon generator24(surface opposing the waveguide23) (refer toFIG. 7) is preferably from 15 to 40 nm, and more preferably from 25 to 30 nm. If the gap G is within the aforementioned range, the light density can be increased, and the light spot diameter of the near-field light irradiated onto the magnetic disk301can be made smaller.

As illustrated inFIG. 5B, the plasmon generator24includes a flat plate part240that partly contacts the upper surface of the pole22e, and the projection part241that projects from the flat plate part240to the waveguide23side. The end surface that becomes a part of the head part end surface12aforms a near-field light generating end surface24a.

As is made clear inFIG. 5AandFIG. 5B, the projection part241opposes the waveguide23via a buffer portion40, and extends to the near-field light generating end surface24a. Thereby, the projection part241can realize a function of propagating the surface plasmon excited by the laser light (waveguide light) that propagates through the waveguide23. In other words, the plasmon generator24is coupled to the waveguide light in surface plasmon mode, and propagates 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 protrusion height TPGCof the projection part241is preferably from 20 to 30 nm. Further, the width WPGCon the near-field light generating end surface24ain the Y direction of the projection part241is smaller than the wavelength of the laser light (waveguide light)63, and is preferably from 15 to 30 nm. Furthermore, the height TPGfrom the lower end (surface that contacts the upper surface of the pole22e) of the flat plate part240to the upper end (upper end surface) of the projection part241when viewed from the air bearing surface side so that the waveguide23is positioned closer to the trailing side than the plasmon generator24, is preferably from 45 to 75 nm, but approximately 60 nm is more preferable. Moreover, the length HPGof the plasmon generator24in the X direction is preferably from 1.0 to 1.4 μm, but approximately 1.2 μm is more preferable. Because the plasmon generator24and the projection part241have the aforementioned size, the light spot diameter of the near-field light irradiated onto the magnetic disk301can be made smaller.

With the present embodiment, the shape of the upper surface of the projection part241is rectangular. However, as illustrated inFIG. 6, the shape of the upper surface of the projection part241can be trapezoidal, configured from a short side positioned on the head part end surface12a, a long side positioned on the head part back end surface12bside, and two oblique sides each connecting the end parts of the long and short sides, and the width in the Y direction gradually increases from the head part end surface12atoward the head part back end surface12bside. With this shape, the light density of the near-field light irradiated onto the magnetic disk301can be increased, and the light spot diameter can be made smaller. In this case, the angle θ formed by the X axis and each of the two oblique sides of the trapezoid shape of the upper surface of the projection part241is preferably less than 10°, more preferably from 1 to 3°, and approximately 2° is particularly preferred.

As illustrated inFIGS. 5A and 5B, a portion of the flat plate part240of the plasmon generator24, which is made of a metal material, interfaces with the pole22e, which is similarly made of a metal material. Thereby, the plasmon generator24is not in an electrically isolated state, and the negative effects caused by electrostatic discharge (ESD) are suppressed.

Furthermore, the flat plate part240can realize a function of causing the heat generated by the near-field light generating portion NFP at the near-field light generating end surface24aof the plasmon generator24to escape from the near-field light generating portion NFP. As a result, excess temperature increase of the plasmon generator24is suppressed. This can contribute to the avoidance of a major drop in the light use efficiency of the plasmon generator24and unnecessary protrusion of the near-field light generating end surface24a. Furthermore, the heat can be suppressed by escaping to the pole22eside, and therefore degradation of the pole22edue to heat can be suppressed.

The length HPG(seeFIG. 5B) in the height direction (X direction) of the plasmon generator24is preferably equal to or longer than the length of the pole22ein this direction. If the length in the height direction (X direction) of the plasmon generator24is shorter than the length of the pole22e, there is a risk that the laser light (waveguide light) that propagates through the waveguide23is lost by the existence of the pole22e, and that the light intensity is reduced.

The plasmon generator24is preferably formed of a conductive material, such as a metal (e.g., Pd, Pt, Rh, Ir, Ru, Au, Ag, Cu or Al) or an alloy made of at least two types of these metals.

The waveguide23is provided on the +Z side (trailing side) of the plasmon generator24. With such a configuration, the waveguide23can be separated from the pole22e. As a result, a case can be avoided, in which the amount of light to be converted to the near-field light decreases as a part of the laser light (waveguide light)63is absorbed by the pole22eformed by metal.

Regarding the shape of the waveguide23, the width in the track width direction (Y axis direction) may be constant. However, the width of a part of the waveguide23on the side of the head part end surface12amay be narrower in the track width direction (Y axis direction) as shown inFIG. 5A. The width WWG1in the track width direction (Y axis direction) at a part of the rear end surface23athat is on the opposite side from the head part end surface12aof the waveguide23is approximately 0.5-20 μm, for example. The width WWG2in the track width direction (Y axis direction) at the part on the side of the end surface23bis approximately 0.3-100 μm, for example. The thickness TWGof the part on the side of the rear end surface23a(in the Z axis direction) is approximately 0.1-4 μm, for example. The height (length) HWG(in the X axis direction) is approximately 10-300 μm, for example.

The side surfaces of the waveguide23, that is, the upper surface, the lower surface and both side surfaces in the track width direction (Y axis direction) contact the passivation layer31(FIG. 4), except the part that contacts the buffer portion40. The waveguide23is configured from a material formed by spattering or the like, that has a refractive index nWG, which is higher than the refractive index nOCof the material forming the passivation layer31. For example, if the wavelength λLof the laser light is 600 nm, and if the passivation layer31is formed by SiO2(silicon dioxide; n=1.46), the waveguide23may be formed by Al2O3(alumina; n=1.63). In addition, if the passivation layer31is formed by Al2O3(n=1.63), the waveguide23may be formed by 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). By forming the waveguide23with such materials, propagation loss of the laser light (waveguide light)63can be suppressed with excellent optical characteristics that the materials have themselves. Further, while the waveguide functions23as a core, the passivation layer31functions as a cladding, thereby establishing the condition for total reflection by the entire side surfaces. As a result, more laser light (waveguide light)63reaches the position of the buffer portion40, and thus, the propagation efficiency of the waveguide23increases.

Further, the waveguide23may have a multilayer structure of dielectric materials and may have a configuration that the refractive index n increases in the upper layers. For example, such a multilayer structure may be established by sequentially laminating dielectric materials based on SiOxNyas a composition ratio for X and Y is appropriately varied. The number of laminated layers may be 8-12, for example. As a result, if the laser light (waveguide light)63is linearly polarized light in the Z axis direction, the laser light (waveguide light)63can propagate to the side of the buffer portion40along the Z axis direction. At that time, by selecting the composition of each layer in the multilayer structure, the layer thickness and the number of layers, the desired propagative position for the laser light (waveguide light)63in the Z axis direction can be obtained.

The buffer portion40is formed by a dielectric material that has a lower refractive index nBFthan the refractive index nWGof the waveguide23. If the wavelength λLof the laser light is 600 nm, and if the waveguide23is formed by Al2O3(alumina; n=1.63), the buffer portion40may be formed by SiO2(silicon dioxide; n=1.46). In addition, if the waveguide23is formed by Ta2O5(n=2.16), the buffer portion40may be formed by SiO2(n=1.46) or Al2O3(n=1.63). In these cases, the buffer portion40may be configured as a part of the passivation layer31(FIG. 3), which is formed by SiO2(n=1.46) or Al2O3(n=1.63) and functions as a cladding. Moreover, the length LBF(in the X axis direction) of the buffer portion40, which is sandwiched by the side surface23cof 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 such a case, the buffer portion40becomes a significantly larger area compared to the so-called “focal area” that is formed when the laser light is concentrated at the buffer portion40and the plasmon generator24for coupling in the surface plasmon mode. Therefore, coupling in the extremely stable surface plasmon mode becomes possible. The thickness TBF(in the Z axis direction) of the buffer portion40is preferably 10-200 nm. These length LBFand thickness TBFof the buffer portion40are important parameters for achieving appropriate excitation and propagation for the surface plasmon.

FIG. 7is a plan view illustrating a shape of the waveguide23, plasmon generator24, and electromagnetic transducer element22on or near the head part end surface of a thermally-assisted magnetic recording head1according to the present embodiment.

As illustrated inFIG. 7, the pole22eextends to the head part end surface12ain the electromagnetic transducer element22. Herein, the end surface221on the head part end surface12aof the pole22ehas an approximately rectangular shape such as a rectangle, square, or a trapezoid or the like, for example.

On the head part end surface12a, the plasmon generator24has a flat plate part240with a predetermined thickness that partly contacts the pole22e. A top side NFP of the projection part241of the plasmon generator24is separated from the pole22eand thereby can function as a near-field light emitting point.

Next, the function of the thermally-assisted magnetic recording head1according to the present embodiment having the aforementioned configuration is described.FIG. 8is a schematic diagram for describing thermally-assisted magnetic recording using a surface plasmon mode in a thermally-assisted magnetic recording head1according to the present embodiment.

As illustrated inFIG. 8, when information is written to the magnetic recording layer of the magnetic disk301by the electromagnetic transducer element22, first the laser light (waveguide light)63radiated from the laser diode60of the light source unit50propagates through the waveguide23. Next, the laser light (waveguide light)63that has advanced to the vicinity of the buffer portion40couples to the optical configuration formed by the waveguide23having a refractive index nWG, the buffer portion40having a refractive index nBF, and the plasmon generator24formed of a conductive material such as a metal, and induces the surface plasmon mode on the projection part241of the plasmon generator24. In other words, the laser light63is coupled to the plasmon generator24in the surface plasmon mode. Actually, from the optical interfacial state between the waveguide23, which is a core, and the buffer portion40, evanescent light is excited in the buffer portion40. Next, the surface plasmon mode is induced and surface plasmon is excited by a form in which the evanescent light and a fluctuation on a charge excited on the metal surface (projection part241) of the plasmon generator24are coupled with each other. Precisely, because the surface plasmon, which is the elementary excitation in this system, is coupled to the electromagnetic wave, it is a surface plasmon polariton that is excited. However, the surface plasmon polariton is abbreviated and simply referred to as surface plasmon hereinafter. This surface plasmon mode can be induced by setting the refractive index nBFof the buffer portion40to be smaller than the refractive index nWGof the waveguide23(nBF<nWG) and by appropriately selecting a length of the buffer portion40(in the X direction), that is the length LBFof the coupling part between the waveguide23and the plasmon generator24(length HPCof the plasmon generator24in the X direction), and the thickness TBFof the buffer portion40(in the Z direction) (the gap G between the waveguide23and the projection part241; preferably from 15 to 40 nm and more preferably from 25 to 30 nm).

In the induced surface plasmon mode, the surface plasmon70is excited on the projection part241of the plasmon generator24and propagates on the projection part241along the direction of arrow71. The projection part241is not in contact with the pole22e, and therefore is not negatively affected by the pole22ethat has not been adjusted for efficiently exciting the surface plasmon. As a result, the surface plasmon intentionally propagates on the projection part241.

As described above, when the surface plasmon70propagates in the direction of arrow71on the projection part241, the surface plasmon70, that is, the electric field is concentrated on the near-field light generating portion NFP on the near-field light generating end surface24a, which is the destination of the projection part241that extends to the head part end surface12a. As a result, near-field light72is generated from the near-field light generating portion NFP. The near-field light72is irradiated towards the magnetic recording layer of the magnetic disk301, reaches the surface of the magnetic disk301, and heats the magnetic recording layer part of the magnetic disk301. Therefore, an anisotropic magnetic field (coercive force) of that part decreases to a value at which the writing can be performed, and writing is performed by the magnetic field applied to that part.

Herein, with the present embodiment, the plasmon generator24is positioned closer to the trailing side than the pole22eand therefore the part where the writing magnetic field is applied directly below the pole22emoves relatively and be heated by the near-field light. Therefore, after heating by the near-field light has occurred, a magnetic field is applied to the magnetic microparticles with unstable magnetization during the cooling process. Therefore, rapid magnetization reversal can occur in the magnetic domain adjacent to the magnetic disk301because of the magnetic field that was applied, and thus, the requirements for high recording density and sufficient S/N ratio can be satisfied.

Furthermore, because the plasmon generator24of the present embodiment includes the flat plate part240that contacts with the pole22eand the projection part241that projects to the waveguide23side, the light density of the near-field light generated from the near-field light generating portion NFP of the projection part241and irradiated onto the magnetic disk301can be increased, and the light spot diameter can be reduced. Therefore, even higher recording density can be accommodated.

Moreover, heating due to the generation of near-field light72occurs in the vicinity of the near-field light generating portion NFP of the near-field light generating end surface24a, but this heat escapes to the flat plate part240of the plasmon generator24. As a result, excess temperature increase of the plasmon generator24is suppressed, and this can contribute to the avoidance of a major drop in the light use efficiency of the plasmon generator24and unnecessary protrusion of the near-field light generating end surface24a. Moreover, the heat can be suppressed from escaping to the pole22eside, and therefore, degradation and the like of the pole22edue to the heat that escapes to the pole22eside can also be suppressed.

The thermally-assisted magnetic recording head with the aforementioned configuration can be manufactured as described below.

FIGS. 9A-9Eare schematic diagrams illustrating steps for forming the plasmon generator24of the thermally-assisted magnetic recording head1according to the present embodiment. All of the drawings (FIG. 9A-9E) are plan views illustrating a YZ plane as seen from the air bearing surface side.

As illustrated inFIG. 9A, a metal layer90of a predetermined thickness (for example, approximately 60 nm) made of Au, an Au alloy or the like is formed using a sputtering method, for example, so as to cover the pole22eformed from a magnetic material such as FeCo or the like and planarized using a polishing method such as chemical mechanical polishing (CMP). This metal layer90later becomes the plasmon generator24.

Next, as illustrated inFIG. 9B, a photoresist layer91is formed so as to cover the metal layer90, and then patterned. The metal layer90below the portion of the photoresist layer91that remains after the patterning later becomes the projection part241of the plasmon generator24, and the other areas become the flat plate part240of the plasmon generator24.

Next, as illustrated inFIG. 9C, etching is performed using a dry etching method, such as ion milling or the like, such that the remaining photoresist layer91becomes a mask and that the thickness of the metal layer90in the areas where the photoresist layer does not exist becomes a predetermined thickness (for example, approximately 30 nm). Thereby, the plasmon generator24is formed with the flat plate part240and the projection part241.

Thereafter, as illustrated inFIG. 9D, a protective layer92made of Al2O3(alumina) or SiO2is formed so as to cover the plasmon generator24and the photoresist layer91, and after lift-off, an insulation layer93made of Al2O3(alumina) is formed using a sputtering method or the like so as to cover the protective layer92. The insulation layer93later forms a gap, that is the buffer portion40, between the plasmon generator24(projection part241) and the waveguide23. The thickness of the insulation layer93has an effect on the coupling efficiency of the laser light (waveguide light)63to the projection part241of the plasmon generator24, and therefore the film thickness of the insulation layer93must be controlled to a suitable thickness.

Finally, as illustrated inFIG. 9E, the head part12of the present embodiment can be manufactured by forming the waveguide23by forming and patterning a TaOXfilm on the insulation layer93, and then forming a protective layer31made of Al2O3(alumina) or SiO2.

With the aforementioned manufacturing method, the gap G between the waveguide23and the plasmon generator24(projection part241) can easily be controlled by controlling the film thickness of the insulation layer93. Therefore, the thermally-assisted magnetic recording head1that can sufficiently reduce the light spot diameter of the near-field light that is irradiated onto the magnetic disk301can easily be manufactured.

The aforementioned embodiment is provided to aid in understanding the present invention, and is not provided to restrict the present invention. Therefore, each of the elements disclosed in the aforementioned embodiment also includes any design changes and equivalents thereof that belong to the technical scope of the present invention.

In the aforementioned embodiment, the flat plate part240of the plasmon generator24is provided on the pole22e, but the present invention is not restricted to this configuration. For example, as illustrated inFIG. 10, a configuration is also acceptable where a portion of the pole22eis embedded into the bottom surface side of the flat plate part240of the plasmon generator24. By using this configuration, the thickness of the flat plate part240of the plasmon generator24is increased, and the heat dispersing effect can be enhanced, while at the same time the light density of the near-field light irradiated onto the magnetic disk301can be increased and the light spot diameter can be made even smaller. Furthermore, the distance between the pole22eand the near-field light generating portion NFP of the projection part241is reduced, and the magnetic field required for writing can be applied.

Furthermore, with the above-described embodiment, the pole22ehas approximately a rectangular solid shape, but the present invention is not restricted to this configuration. For example, as illustrated inFIG. 11, a configuration is also acceptable where at least a portion of the surface of the leading side of the pole22eis sloped such that the projection area of the pole22egradually increases toward the X direction when viewed from the head part end surface12aside. Thereby, the magnetic flux guided by the linking layer22b(refer toFIG. 4), the upper part yoke layer22c, and the pole22ecan be even further concentrated in the vicinity of the near-field light generating portion NFP.

Furthermore, with the aforementioned embodiment, when the projection part241projecting from the flat plate part240of the plasmon generator24is viewed from the head part end surface12aside, the shape of the projection part241is rectangular, but the present invention is not restricted to this configuration, and the shape of the projection part241can be essentially a trapezoidal shape or essentially an inverted trapezoidal shape or the like when the projection part241is viewed from the head part end surface12aside, and a shape is also acceptable where the angle of intersection between the flat plate part240and the side edge (side in the Z direction) of the projection part241is rounded when the projection part241is viewed from the head part end surface12aside.

With the aforementioned embodiment, a part of the flat plate part240of the plasmon generator24contacts upper surface of the pole22e. However, the present invention is not restricted to this configuration, and the lower surface of the flat plate part240of the plasmon generator24and the upper surface of the pole22ecan be separated by a predetermined distance, and in this case, an insulation layer made of Al2O3(alumina) or the like can be interposed between the flat plate part240of the plasmon generator and the pole22e.

EXAMPLES

The present invention is described in further detail by presenting experimental examples. However, the present invention is in no way restricted to the following experimental examples and the like.

Simulation analysis experiments were performed as described below for the magnetic field intensity of the magnetic field generated by the pole in the thermally-assisted magnetic recording head, directly below (heating point) the near-field light generating portion NFP.

The simulation analysis experiments were performed using a three-dimensional finite-difference time-domain method (FDTD method) which is electromagnetic field analysis.

The thermally-assisted magnetic recording head of the present embodiment is the thermally-assisted magnetic recording head1illustrated inFIGS. 5A and 5Bthat implements a model where the pole22eis formed from a FeCo alloy. Furthermore, in this model, the width in the Y direction of the pole22e(track width direction) was 0.3 μm, and the end surface of the upper part yoke layer22con the head part end surface12awas located at a position recessed by 0.2 μm in the X direction (height direction) from the head part end surface12a. Furthermore, the number of windings in the writing coil22dwas 3, and the input current value was 40 mA.

Furthermore, with the extreme trailing side of the pole22e(contact point between the plasmon generator24and the flat plate part240) as seen from the ABS11aas the origin, a magnetic field intensity corresponding to the distance in the down track direction was calculated by simulation analysis, and a relationship between the distance and the magnetic field intensity in the down track direction was determined.

The results of the simulation analysis experiment are illustrated inFIG. 12.FIG. 12is a graph illustrating the results of the simulation analysis experiment. The portion of the graph where the horizontal axis value is 0 indicates the extreme trailing side of the pole22e(contact point with the flat plate part240), and the right side of the graph indicates the side that is trailing the contact point, while the left side of the graph indicates the side that is leading the contact point.

As illustrated inFIG. 12, it was confirmed that a magnetic field with the necessary intensity for writing (magnetization reversal) could be applied even at a point 60 to 70 nm away from the pole22eto the trailing side. From the results, it is understood that, if the waveguide23is positioned closer to the trailing side than the plasmon generator24such that the distance between the upper end (upper end surface) of the projection part241of the plasmon generator24and the lower end (surface that contacts the upper surface of the pole22e) of the flat plate part240when viewed from the air bearing surface side, that is the thickness TPGof the plasmon generator24, is a predetermined length (approximately 75 nm or less), stable magnetization reversal is possible because of the heating by the near-field light that is irradiated from the plasmon generator24located closer to the trailing side than the pole22e.

Experimental Example 2

Using the model used in experimental example 1, the waveguide23was positioned closer to the trailing side than the plasmon generator24, such that the distance between the upper end (upper end surface) of the projection part241of the plasmon generator24and the lower end (surface that contacts the upper surface of the pole22e) of the flat plate part240when viewed from the air bearing surface side, that is the thickness TPGof the plasmon generator24, was 70 nm, and the magnetic field intensity directly below the near-field light generating portion NFP of the plasmon generator24when the width in the Y direction of the pole22e(track width direction) was varied in a range from 0.06 to 0.4 μm was calculated from the simulation analysis similar to experimental example 1. Then, the relationship between the magnetic field intensity and the pole width was determined.

The results of the simulation analysis experiment are illustrated inFIG. 13.FIG. 13is a graph illustrating the results of the simulation analysis experiment. As illustrated inFIG. 13, it is understood that the width in the Y direction (track width direction) of the pole22eis preferably from 0.2 to 0.3 μm in order to apply a suitable magnetic field of the intensity required for writing (magnetization reversal) directly below the near-field light generating portion NFP.

Experimental Example 3

A simulation analysis experiment was performed as described below concerning the relationship between the shape of the plasmon generator, near-field light peak intensity (V2m2), and the light spot diameter of the near-field light (in cross track direction and down track direction), based on the generation of near-field light by the near-field light generating optical system of the thermally-assisted magnetic recording head. With the present experimental example, the light spot diameter of the near-field light refers to the length in a predetermined direction (the cross track direction and the down track direction) in a cut plane when the light density distribution of the near-field light generated from the near-field light generating surface24ais integrated, the integrated light density distribution is cut in half along a predetermined horizontal plane, and the light density distribution in one direction that includes a vertex of the light density distribution specifies a horizontal plane that includes light density that is 20% of the total light density after integrating.

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

The present experimental example implemented a model where the waveguide23of the thermally-assisted magnetic recording head1illustrated inFIGS. 5A and 5Bwas formed from Ta2O5(refractive index nWG=2.15) with a cross section having a width in the Y direction of 600 nm and a thickness in the Z direction of 400 nm, the protective layer31that realizes a function of cladding was formed from SiO2(refractive index nBF=1.46), and the pole22ewas formed from a FeCo alloy with a width in the Y direction of 0.3 μm. Furthermore, with this model, the protrusion height TPGCof the projection part241of the plasmon generator24was 30 nm, the width in the Y direction of the projection part241was 20 nm, the gap G between the lower surface of the waveguide23and the upper surface of the projection part241was 25 nm, the height TPGof the plasmon generator24was 60 nm, and the length HPGin the X direction of the plasmon generator was 1.2 μm (first embodiment). Using this model, a simulation analysis experiment was performed where the laser light incident to the waveguide23was a Gaussian beam (15 mW) with transverse magnetic (TM) polarized light (the direction of oscillation of the laser light is in the direction perpendicular to the layer surface of the waveguide23; Z direction) and having a wavelength of 800 nm.

As comparative examples, a simulation analysis experiment was performed in a manner similar to the aforementioned first embodiment on both a model (comparative example 1) where a pole with a triangular shape on an end surface when viewed from the ABS11a, an inverted V-shaped plasmon generator that covers the pole, and the waveguide are provided as illustrated inFIG. 14and where the distance between the vertex of the inverted V of the plasmon generator and the vertex of the triangular pole (vertex located to the extreme trailing side) was 60 nm, and a model (comparative example 2) where a pole with a rectangular shape on the end surface when viewed from the ABS11a, a triangular plasmon generator provided on the pole, and the waveguide are provided as illustrated inFIG. 15and where the distance between the pole and the vertex of the plasmon generator (vertex located on the extreme trailing side) was 100 nm. It is noted that the models of comparative examples 1 and 2 have configurations similar to the model of the first embodiment, except that the shape of the pole and the plasmon generator are different. The results of the simulation analysis experiment are shown in Table 1.

As shown in Table 1, it can be understood that with the thermally-assisted magnetic recording head having the configuration of first embodiment, the near-field light peak intensity (light density) can be increased, and the light spot diameter (particularly the light spot diameter in the cross track direction) can be reduced.

Experimental Example 4

A simulation analysis experiment was performed as described below on the relationship between the length in the X direction of the plasmon generator and the gap between the waveguide lower surface and the upper surface of the projection part of the plasmon generator, using the generation of near-field light by the near-field light generating optical system of the thermally-assisted magnetic recording head.

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

A simulation analysis was performed for the present experimental example using a model with essentially the same configuration as the configuration of the first embodiment in the aforementioned experimental example 3, by changing the gap G between the upper surface of the projection part241of the plasmon generator24and the lower surface of the waveguide23within a range of 5 to 50 nm, changing the length HPGin the X direction of the plasmon generator within a predetermined range, and calculating the near-field light peak intensity. The results of the simulation analysis experiment are illustrated inFIG. 16.

FIG. 16is a graph illustrating the results of the simulation analysis experiment. As illustrated inFIG. 16, it was confirmed that the length HPGin the X direction of the plasmon generator24is preferably in a range of 0.1 to 1.4 μm in order to obtain the desired light peak intensity (light density). Furthermore, it was confirmed that the gap G between the lower surface of the waveguide23and the upper surface of the projection part241of the plasmon generator24is preferably in a range of 15 to 40 nm in order to obtain the desired light peak intensity (light density).

Experimental Example 5

A simulation analysis experiment was performed as described below on the relationship to the shape of the upper surface of the projection part of the plasmon generator, based on the generation of near-field light by the near-field light generating optical system of the thermally-assisted magnetic recording head.

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

A simulation analysis was performed for the present experimental example using a model with a configuration that is essentially the same as the configuration of the first embodiment in the aforementioned experimental example 3 except that the shape of the upper surface of the projection part241of the plasmon generator24was the shape illustrated inFIG. 6, wherein the angle θ formed between the X direction and each of the two oblique sides of the upper surface of the projection part241of the plasmon generator24was changed within a range of 0 to 20°, and then the near-field light peak intensity was calculated. The results of the simulation analysis experiment are illustrated inFIG. 17.

FIG. 17is a graph illustrating the results of the simulation analysis experiment. As illustrated inFIG. 17, it was confirmed that the angle θ formed between the X direction and each of the two oblique sides of the upper surface of the projection part241of the plasmon generator24is preferably greater than 0° and less than 10°, in order to increase the near-field light peak intensity (light density).

Experimental Example 6

A simulation analysis experiment was performed as described below on the relationship to the shape of the plasmon generator, based on the generation of near-field light by the near-field light generating optical system of the thermally-assisted magnetic recording head.

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

A simulation analysis was performed for the present experimental example, using a model with a configuration that is essentially the same as the configuration of the first embodiment in the aforementioned experimental example 3, except that the shape of the plasmon generator24was the shape illustrated inFIG. 10, wherein the protrusion height TPGCof the projection part241was changed within a range of 20 to 45 nm, the thickness of the plasmon generator24on the pole22e(length TPGfrom the lower end (surface that contacts the upper surface of the pole22e) of the plasmon generator24(flat plate part240) when viewed from the air bearing surface side to the upper end (upper end surface) of the projection part241, such that the waveguide23is positioned closer to the trailing side than the plasmon generator24) was changed from 40 to 100 nm, and then the near-field light peak intensity and the light spot diameter in the cross track direction were calculated. The results of the simulation analysis experiment are illustrated inFIG. 18andFIG. 19.

FIG. 18is a graph showing the results of the simulation analysis experiment based on the calculation results for the near-field light peak intensity, andFIG. 19is a graph showing the results of the simulation analysis experiment based on the calculated results for the light spot diameter.

As illustrated inFIG. 18, it was confirmed that the protrusion height TPGCof the projection part241is preferably from 20 to 30 nm in order to increase the near-field light peak intensity (light density). Furthermore, it was confirmed that although the near-field light peak intensity (light density) can be increased by increasing the thickness TPGof the plasmon generator24on the pole22e, when the thickness is 55 nm or higher, the dependency of the near-field light peak intensity (light density) to the thickness TPGof the plasmon generator24becomes weaker. Therefore, it was confirmed that a thickness TPGof 45 to 75 nm is practical.

Furthermore, as illustrated inFIG. 19, it is understood that when the protrusion height TPGCof the projection part241is low (for example less than 20 nm), the light spot diameter in the cross track direction increases and is not suitable for higher recording densities. Therefore, it was confirmed that the protrusion height TPGCof the projection part241is preferably 20 nm or higher in order to support higher recording densities.