Thermally-assisted magnetic recording head having a plasmon generator

A thermally-assisted magnetic recording head includes a waveguide having a core and a cladding, and a plasmon generator. The core has an evanescent light generating surface. The plasmon generator has a plasmon exciting part opposed to the evanescent light generating surface. Assuming a virtual straight line that passes internally through the core and that is parallel to the direction of travel of light propagating through the core, at least part of the evanescent light generating surface and at least part of the plasmon exciting part are both inclined relative to the virtual straight line such that the distance from the virtual straight line decreases with increasing proximity to the medium facing surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermally-assisted magnetic recording head for use in thermally-assisted magnetic recording where a recording medium is irradiated with near-field light to lower the coercivity of the recording medium for data writing.

2. Description of the Related Art

Recently, magnetic recording devices such as magnetic disk drives have been improved in recording density, and thin-film magnetic heads and recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a read head section including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head section including an induction-type electromagnetic transducer for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of a recording medium. The slider has a medium facing surface that faces the recording medium.

To increase the recording density of a magnetic recording device, it is effective to make the magnetic fine particles of the recording medium smaller. Making the magnetic fine particles smaller, however, causes the problem that the magnetic fine particles drop in the thermal stability of magnetization. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the recording medium, and this makes it difficult to perform data writing with existing magnetic heads.

To solve the foregoing problems, there has been proposed a technology so-called thermally-assisted magnetic recording. The technology uses a recording medium having high coercivity. When writing data, a write magnetic field and heat are simultaneously applied to the area of a recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization. Hereinafter, a magnetic head for use in thermally-assisted magnetic recording will be referred to as a thermally-assisted magnetic recording head.

In thermally-assisted magnetic recording, near-field light is typically used as a means for applying heat to the recording medium. A known method for generating near-field light is to use a plasmon generator, which is a piece of metal that generates near-field light from plasmons excited by irradiation with laser light. The laser light to be used for generating the near-field light is typically guided through a waveguide, which is provided in the slider, to the plasmon generator disposed near the medium facing surface of the slider.

U.S. Patent Application Publication No. 2007/0139818 A1 discloses a thermally-assisted magnetic recording head configured to excite plasmons on a plasmon generator (a near-field-light generating layer) by directly irradiating the plasmon generator with laser light.

U.S. Patent Application Publication No. 2010/0172220 A1 discloses a thermally-assigned magnetic recording head in which a plasmon generator (a surface plasmon antenna) is arranged to face the outer surface of a waveguide (a core) with a predetermined distance therebetween, so that light propagating through the waveguide is totally reflected at the outer surface of the waveguide to thereby generate evanescent light that is used to excite surface plasmons on the plasmon generator.

The configuration in which the plasmon generator is directly irradiated with laser light to excite plasmons on the plasmon generator, such as one disclosed in U.S. Patent Application Publication No. 2007/0139818 A1, has a number of problems as follows. First, this configuration has the problem of low efficiency of transformation of laser light into near-field light because most part of the laser light is reflected at the surface of the plasmon generator or transformed into thermal energy and absorbed by the plasmon generator. Further, this configuration has the problem that the plasmon generator greatly increases in temperature when it absorbs thermal energy, and this may result in corrosion of the plasmon generator. Further, this configuration has the problem that the plasmon generator expands as it increases in temperature, and may thus protrude from the medium facing surface to cause damage to a recording medium or to itself.

The configuration in which evanescent light is used to excite surface plasmons on a plasmon generator, such as one disclosed in U.S. Patent Application Publication No. 2010/0172220 A 1, provides higher efficiency of transformation of laser light into near-field light when compared with the case of directly irradiating the plasmon generator with laser light. This makes it possible to resolve the above-described problems.

In the thermally-assisted magnetic recording head disclosed in U.S. Patent Application No. 2010/0172220 A1, the evanescent-light-generating portion of the outer surface of the waveguide and a part of the outer surface of the plasmon generator that is opposed to the aforementioned portion are both arranged parallel to the direction of travel of the laser light propagating through the waveguide. This configuration allows only a small amount of the entire laser light propagating through the waveguide to reach the evanescent-light-generating portion of the outer surface of the waveguide. It is thus difficult with this configuration to generate much evanescent light and to thereby excite a lot of surface plasmons on the plasmon generator.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermally-assisted magnetic recording head that is configured to excite surface plasmons on a plasmon generator by using evanescent light, and allows a lot of surface plasmons to be excited on the plasmon generator.

A thermally-assisted magnetic recording head of the present invention includes: a medium facing surface that faces a recording medium; a main pole; a waveguide; and a plasmon generator. The main pole has an end face located in the medium facing surface, and produces a write magnetic field for writing data on the recording medium. The waveguide includes a core through which light propagates, and a cladding that surrounds the core. The plasmon generator has a near-field light generating part located in the medium facing surface.

The core has an evanescent light generating surface that generates evanescent light based on the light propagating through the core. The plasmon generator has a plasmon exciting part that is opposed to the evanescent light generating surface with a predetermined distance therebetween. The cladding includes an interposer interposed between the evanescent light generating surface and the plasmon exciting part.

A virtual straight line is assumed for the thermally-assisted magnetic recording head of the present invention. The virtual straight line passes internally through the core and is parallel to the direction of travel of the light propagating through the core. At least part of the evanescent light generating surface and at least part of the plasmon exciting part are both inclined relative to the virtual straight line such that the distance from the virtual straight line decreases with increasing proximity to the medium facing surface.

In the thermally-assisted magnetic recording head of the present invention, the plasmon generator is configured so that a surface plasmon is excited on the plasmon exciting part through coupling with the evanescent light generated from the evanescent light generating surface, the surface plasmon propagates to the near-field light generating part, and the near-field light generating part generates near-field light based on the surface plasmon.

In the thermally-assisted magnetic recording head of the present invention, the at least part of the evanescent light generating surface and the at least part of the plasmon exciting part may each form an angle in the range of 10° to 35° or in the range of 10° to 20° relative to the virtual straight line.

In the thermally-assisted magnetic recording head of the present invention, the plasmon exciting part may be a surface. In this case, the plasmon exciting part may include a width changing portion. The width changing portion has a width in a direction parallel to the medium facing surface and the evanescent light generating surface, the width decreasing with increasing proximity to the medium facing surface.

In the thermally-assisted magnetic recording head of the present invention, the plasmon generator may be interposed between the core and the main pole.

In the thermally-assisted magnetic recording head of the present invention, at least part of the evanescent light generating surface of the core and at least part of the plasmon exciting part of the plasmon generator are both inclined relative to the aforementioned virtual straight line such that the distance from the virtual straight line decreases with increasing proximity to the medium facing surface. This allows a larger amount of the entire light propagating through the core to reach the evanescent light generating surface than in the case where the evanescent light generating surface and the plasmon exciting part are arranged parallel to the direction of travel of the light propagating through the core. Consequently, according to the present invention, it is possible to produce much evanescent light from the evanescent light generating surface and to thereby excite a lot of surface plasmons on the plasmon generator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, reference is made toFIG. 1toFIG. 6to describe the configuration of a thermally-assisted magnetic recording head according to a first embodiment of the invention.FIG. 1is a cross-sectional view showing the main part of the thermally-assisted magnetic recording head.FIG. 2is a perspective view showing the main part of the thermally-assisted magnetic recording head.FIG. 3is a cross-sectional view showing the configuration of the thermally-assisted magnetic recording head.FIG. 4is a front view showing the medium facing surface of the thermally-assisted magnetic recording head.FIG. 5is a plan view showing a first example of the main pole.FIG. 6is a plan view showing a second example of the main pole.

The thermally-assisted magnetic recording head according to the present embodiment is for use in perpendicular magnetic recording, and is in the form of a slider to fly over the surface of a recording medium that rotates. When the recording medium rotates, an airflow passing between the recording medium and the slider causes a lift to be exerted on the slider. The slider is configured to fly over the surface of the recording medium by means of the lift.

As shown inFIG. 3, the thermally-assisted magnetic recording head has a medium facing surface60that faces the recording medium. Here, X direction, Y direction, and Z direction will be defined as follows. The X direction is the direction across the tracks of the recording medium, i.e., the track width direction. The Y direction is a direction perpendicular to the medium facing surface60. The Z direction is the direction of travel of the recording medium as viewed from the slider. The X, Y, and Z directions are orthogonal to one another.

As shown inFIG. 3andFIG. 4, the thermally-assisted magnetic recording head includes: a substrate1made of a ceramic material such as aluminum oxide-titanium carbide (Al2O3—TiC) and having a top surface1a; an insulating layer2made of an insulating material such as alumina (Al2O3) and disposed on the top surface1aof the substrate1; a bottom shield layer3made of a magnetic material and disposed on the insulating layer2; a bottom shield gap film4which is an insulating film disposed to cover the bottom shield layer3; a magnetoresistive (MR) element5serving as a read element disposed on the bottom shield gap film4; two leads (not shown) connected to the MR element5; a top shield gap film6which is an insulating film disposed on the MR element5; and a top shield layer7made of a magnetic material and disposed on the top shield gap film6. The Z direction is also a direction perpendicular to the top surface1aof the substrate1.

An end of the MR element5is located in the medium facing surface60facing the recording medium. The MR element5may be an element made of a magneto-sensitive film that exhibits a magnetoresistive effect, such as an anisotropic magnetoresistive (AMR) element, a giant magnetoresistive (GMR) element, or a tunneling magnetoresistive (TMR) element. The GMR element may be of either the current-in-plane (CIP) type in which a current used for detecting magnetic signals is fed in a direction generally parallel to the plane of layers constituting the GMR element or the current-perpendicular-to-plane (CPP) type in which the current used for detecting magnetic signals is fed in a direction generally perpendicular to the plane of layers constituting the GMR element.

The parts from the bottom shield layer3to the top shield layer7constitute a read head section. The thermally-assisted magnetic recording head further includes an insulating layer8disposed on the top shield layer7, a middle shield layer9made of a magnetic material and disposed on the insulating layer8, and a nonmagnetic layer10made of a nonmagnetic material and disposed on the middle shield layer9. The insulating layer8and the nonmagnetic layer10are made of alumina, for example.

The thermally-assisted magnetic recording head further includes a return pole layer11made of a magnetic material and disposed on the nonmagnetic layer10, and an insulating layer (not shown) disposed on the nonmagnetic layer10and surrounding the return pole layer11. The return pole layer11has an end face located in the medium facing surface60. The not-shown insulating layer is made of alumina, for example.

The thermally-assisted magnetic recording head further includes: a shield layer12disposed on a part of the return pole layer11in the vicinity of the medium facing surface60; a coupling layer13disposed on another part of the return pole layer11away from the medium facing surface60; an insulating layer14disposed on the remaining part of the return pole layer11and on the not-shown insulating layer; and a coil15disposed on the insulating layer14. The shield layer12and the coupling layer13are each made of a magnetic material. The shield layer12has an end face located in the medium facing surface60. The coil15is planar spiral-shaped and wound around the coupling layer13. The coil15is made of a conductive material such as copper. The insulating layer14is made of alumina, for example.

The thermally-assisted magnetic recording head further includes an insulating layer16disposed around the shield layer12, the coupling layer13and the coil15and in the space between every adjacent turns of the coil15, and two coupling portions17A and17B disposed on the coupling layer13. The coupling portions17A and17B are each made of a magnetic material. Each of the coupling portions17A and17B has a first layer located on the coupling layer13, and a second and a third layer stacked in this order on the first layer. The first layer of the coupling portion17A and the first layer of the coupling portion17B are disposed to align in the track width direction (the X direction). The insulating layer16is made of alumina, for example.

The thermally-assisted magnetic recording head further includes a waveguide. The waveguide includes a core20through which light propagates, and a cladding that surrounds the core20. The core20has an end face20athat is closer to the medium facing surface60, an evanescent light generating surface20bserving as a top surface, a bottom surface20c, and two side surfaces. The end face20amay be located in the medium facing surface60or at a distance from the medium facing surface60.FIG. 1toFIG. 3illustrate an example in which the end face20ais located in the medium facing surface60. The shape and location of the core20will be described in detail later.

The cladding includes cladding layers18,19, and21. The cladding layer18is disposed over the shield layer12, the coupling layer13, the coil15, and the insulating layer16. The core20is disposed on the cladding layer18. The cladding layer19is disposed on the cladding layer18and surrounds the core20. The cladding layer21is disposed over the evanescent light generating surface20bof the core20and the top surface of the cladding layer19.

The core20is made of a dielectric material that transmits laser light to be used for generating near-field light. The laser light emitted from a laser diode (not shown) enters the core20and propagates through the core20. The cladding layers18,19, and21are each made of a dielectric material that has a refractive index lower than that of the core20. For example, the core20may be made of tantalum oxide such as Ta2O5or silicon oxynitride (SiON), whereas the cladding layers18,19, and21may be made of silicon dioxide (SiO2) or alumina.

The first layers of the coupling portions17A and17B are embedded in the cladding layer18. The second layers of the coupling portions17A and17B are embedded in the cladding layer19. The second layer of the coupling portion17A and the second layer of the coupling portion17B are located on opposite sides of the core20in the track width direction (the X direction) and are each spaced from the core20.

The thermally-assisted magnetic recording head further includes a main pole24disposed above the core20in the vicinity of the medium facing surface60, and a plasmon generator40interposed between the core20and the main pole24. The plasmon generator40is configured to excite surface plasmons on the principle to be described later. The plasmon generator40is made of, for example, one of Au, Ag, Al, Cu, Pd, Pt, Rh and Ir, or an alloy composed of two or more of these elements. The shapes and locations of the main pole24and the plasmon generator40will be described in detail later.

The thermally-assisted magnetic recording head further includes a dielectric layer22disposed on the cladding layer21and surrounding the plasmon generator40, a dielectric layer23disposed to cover the plasmon generator40and the dielectric layer22, and a dielectric layer25disposed on the dielectric layer23at a position away from the medium facing surface60. The main pole24is disposed over the dielectric layers23and25. The third layers of the coupling portions17A and17B are embedded in the cladding layer21and the dielectric layers22,23, and25. The dielectric layer22may be made of SiO2or alumina, for example. The dielectric layers23and25may be made of alumina, for example.

The thermally-assisted magnetic recording head further includes a coupling layer26made of a magnetic material and disposed over the third layers of the coupling portions17A and17B and the dielectric layer25, and a dielectric layer27disposed around the main pole24and the coupling layer26. The top surfaces of the main pole24, the coupling layer26, and the dielectric layer27are even with each other. The dielectric layer27is made of alumina, for example.

The thermally-assisted magnetic recording head further includes a coil28disposed on the dielectric layer27, an insulating layer29disposed to cover the coil28, and a yoke layer30made of a magnetic material and disposed over the main pole24, the coupling layer26and the insulating layer29. The yoke layer30magnetically couples the main pole24and the coupling layer26to each other. The coil28is planar spiral-shaped and wound around part of the yoke layer30lying on the coupling layer26. The coil28is made of a conductive material such as copper. The insulating layer29is made of alumina, for example.

The thermally-assisted magnetic recording head further includes a protective layer31disposed to cover the yoke layer30. The protective layer31is made of alumina, for example.

The parts from the return pole layer11to the yoke layer30constitute a write head section. The coils15and28produce magnetic fields corresponding to data to be written on a recording medium. The shield layer12, the return pole layer11, the coupling layer13, the coupling portions17A and17B, the coupling layer26, the yoke layer30, and the main pole24form a magnetic path for passing magnetic fluxes corresponding to the magnetic fields produced by the coils15and28. The coils15and28are connected in series or in parallel so that the magnetic flux corresponding to the magnetic field produced by the coil15and the magnetic flux corresponding to the magnetic field produced by the coil28flow in the same direction through the main pole24. The main pole24allows the magnetic flux corresponding to the magnetic field produced by the coil15and the magnetic flux corresponding to the magnetic field produced by the coil28to pass, and produces a write magnetic field for writing data on the recording medium by means of a perpendicular magnetic recording system.

As has been described, the thermally-assisted magnetic recording head according to the present embodiment includes the medium facing surface60, the read head section, and the write head section. The medium facing surface60faces a recording medium. The read head section and the write head section are stacked on the substrate1. The write head section is located on the front side in the direction of travel of the recording medium (the Z direction) (i.e., located on the trailing side) relative to the read head section.

The write head section includes the coils15and28, the main pole24, the waveguide, and the plasmon generator40. The waveguide includes the core20and the cladding. The cladding includes the cladding layers18,19, and21. The main pole24is located on the front side in the direction of travel of the recording medium (the Z direction) relative to the core20. The core20has the evanescent light generating surface20b. The plasmon generator40is disposed above the evanescent light generating surface20bof the core20and interposed between the core20and the main pole24.

The shapes and locations of the core20and the plasmon generator40will now be described in detail with reference toFIG. 1andFIG. 2. As shown inFIG. 1andFIG. 2, the evanescent light generating surface20bof the core20includes an inclined portion20b1and a horizontal portion20b2, the inclined portion20b1being closer to the medium facing surface60. The inclined portion20b1has a front end portion closer to the medium facing surface60and a rear end portion opposite to the front end portion. The front end portion of the inclined portion20b1may be located in the medium facing surface60or at a distance from the medium facing surface60.FIG. 1andFIG. 2illustrate an example in which the front end portion of the inclined portion20b1is located in the medium facing surface60. The horizontal portion20b2is connected to the rear end portion of the inclined portion20b1.

As shown inFIG. 1andFIG. 2, the plasmon generator40has a plasmon exciting part40aserving as a bottom surface, a top surface40b, two side surfaces40cand40d, a front end face40e, and a rear end face40f. The front end face40eis located in the medium facing surface60and couples the plasmon exciting part40a, the top surface40b, and the two side surfaces40cand40dto each other. The plasmon exciting part40ais opposed to the evanescent light generating surface20bof the core20with a predetermined distance therebetween. The cladding layer21includes an interposer21ainterposed between the evanescent light generating surface20band the plasmon exciting part40a. Since the cladding layer21is part of the cladding, the cladding can be said to include the interposer21a. The plasmon generator40is rectangular, for example, in cross section parallel to the medium facing surface60.

In the present embodiment, the plasmon exciting part40ais a surface. The plasmon exciting part40aincludes an inclined portion40a1and a horizontal portion40a2, the inclined portion40a1being closer to the medium facing surface60. The inclined portion40a1is opposed to the inclined portion20b1of the evanescent light generating surface20b, and has a front end portion located in the medium facing surface60and a rear end portion opposite to the front end portion. The horizontal portion40a2is opposed to the horizontal portion20b2of the evanescent light generating surface20b, and is connected to the rear end portion of the inclined portion40a1. The front end face40ehas a near-field light generating part40glocated at the front extremity of the inclined portion40a1. The near-field light generating part40ggenerates near-field light on the principle to be described later.

Here, assume a virtual straight line that passes internally through the core20and is parallel to the direction of travel of laser light propagating through the core20. InFIG. 3, the arrow with the reference numeral50indicates the direction of travel of the laser light. InFIG. 1, the broken line with the reference letter L represents the aforementioned virtual straight line. The virtual straight line L intersects the end face20aof the core20. The inclined portion20b1, which is part of the evanescent light generating surface20b, and the inclined portion40a1, which is part of the plasmon exciting part40a, are both inclined relative to the virtual straight line L such that the distance from the virtual straight line L decreases with increasing proximity to the medium facing surface60. In other words, the inclined portions20b1and40a1are inclined such that their respective front end portions are located on the rear side in the direction of travel of the recording medium (the Z direction) relative to their respective rear end portions.

As shown inFIG. 1, the angle that the inclined portion20b1of the evanescent light generating surface20bforms relative to the virtual straight line L will be represented by the symbol θ1, and the angle that the inclined portion40a1of the plasmon exciting part40aforms relative to the virtual straight line L will be represented by the symbol θ2. The angles θ1and θ2are preferably in the range of 10° to 35°, and more preferably in the range of 10° to 20°. The reason for this will be described in detail later.

The horizontal portion20b2of the evanescent light generating surface20band the horizontal portion40a2of the plasmon exciting part40aboth extend substantially perpendicularly to the medium facing surface60.

The top surface40bof the plasmon generator40includes an inclined portion40b1and a horizontal portion40b2, the inclined portion40b1being closer to the medium facing surface60. The inclined portion40b1has a front end portion located in the medium facing surface60and a rear end portion opposite to the front end portion. The horizontal portion40b2is connected to the rear end portion of the inclined portion40b1. In the present embodiment, in particular, the inclined portion40b1and the horizontal portion40b2are roughly parallel to the inclined portion40a1and the horizontal portion40a2of the plasmon exciting part40a, respectively. The plasmon generator40has a thickness (dimension in the Z direction) that is generally constant regardless of the distance from the medium facing surface60.

As shown inFIG. 2, the plasmon generator40includes a narrow portion41that is located in the vicinity of the medium facing surface60and a wide portion42that is located farther from the medium facing surface60than is the narrow portion41. The narrow portion41has a bottom surface facing the evanescent light generating surface20bof the core20, a top surface, two side surfaces, and a front end face that couples the bottom surface, the top surface and the two side surfaces to each other. The front end face of the narrow portion41also serves as the front end face40eof the plasmon generator40. The width of the narrow portion41in the direction parallel to the medium facing surface60and the evanescent light generating surface20b(the X direction) may be constant regardless of the distance from the medium facing surface60or may decrease with increasing proximity to the medium facing surface60.

The wide portion42is located on a side of the narrow portion41opposite to the front end face40eand is coupled to the narrow portion41. The width of the wide portion42in the track width direction (the X direction) is the same as that of the narrow portion41at the boundary between the narrow portion41and the wide portion42, and is greater than that of the narrow portion41in the other positions. The wide portion42has a bottom surface facing the evanescent light generating surface20bof the core20, a top surface, two side surfaces, and a rear end face that couples the bottom surface, the top surface and the two side surfaces to each other.

The plasmon exciting part40ais composed of the bottom surface of the narrow portion41and the bottom surface of the wide portion42. The boundary between the bottom surface of the narrow portion41and the bottom surface of the wide portion42is located in the inclined portion40a1. Thus, the inclined portion40a1is composed of the bottom surface of the narrow portion41and a part of the bottom surface of the wide portion42, and the horizontal portion40a2is composed of the remaining part of the bottom surface of the wide portion42.

The plasmon exciting part40aincludes a width changing portion42a. In the present embodiment, the width changing portion42ais particularly a portion of the plasmon exciting part40athat is composed of the bottom surface of the wide portion42. The width changing portion42ahas a width in the direction parallel to the medium facing surface60and the evanescent light generating surface20b(the X direction). This width of the width changing portion42adecreases with increasing proximity to the front end face40e, i.e., with increasing proximity to the medium facing surface60, and becomes equal to the width of the bottom surface of the narrow portion41at the boundary between the width changing portion42aand the narrow portion41.

The width (the dimension in the track width direction (the X direction)) of the front end face40eis defined by the width of the narrow portion41in the medium facing surface60. The width of the front end face40efalls within the range of 5 to 40 nm, for example. The height (the dimension in the Z direction) of the front end face40eis defined by the height of the narrow portion41in the medium facing surface60. The height of the front end face40efalls within the range of 5 to 40 nm, for example.

The shape and location of the main pole24will now be described in detail with reference toFIG. 1andFIG. 3toFIG. 6. As shown inFIG. 1,FIG. 5andFIG. 6, the main pole24has a front end face24alocated in the medium facing surface60, a rear end face24bopposite to the front end face24a, a bottom surface24c, a top surface24d, a connecting surface24e, and two side surfaces24fand24g. The connecting surface24econnects the rear end face24band the bottom surface24cto each other. Further, as shown inFIG. 5andFIG. 6, the main pole24includes a narrow portion24A and a wide portion24B. The narrow portion24A has an end face located in the medium facing surface60and an end portion opposite to the end face. The wide portion24B is connected to the end portion of the narrow portion24A. The wide portion24B is greater than the narrow portion24A in width in the track width direction (the X direction).

The width of the narrow portion24A in the track width direction (the X direction) is generally constant regardless of the distance from the medium facing surface60.FIG. 5shows a first example of the main pole24in which the width of the wide portion24B in the track width direction (the X direction) is the same as that of the narrow portion24A at the boundary between the narrow portion24A and the wide portion24B, and gradually increases with increasing distance from the medium facing surface60, then becoming constant.FIG. 6shows a second example of the main pole24in which the width of the wide portion24B in the track width direction (the X direction) is generally constant regardless of the distance from the medium facing surface60. The narrow portion24A has a length in the range of, for example, 0 to 0.3 μm in the direction perpendicular to the medium facing surface60. Where the length is 0, there is no narrow portion24A and thus the wide portion24B has an end face located in the medium facing surface60.

The distance from the top surface1aof the substrate1to an arbitrary point on each of the bottom surface24cand the connecting surface24eof the main pole24increases with increasing distance from the arbitrary point to the medium facing surface60. The bottom surface24cof the main pole24is opposed to part of the top surface40bof the plasmon generator40with the dielectric layer23interposed therebetween.

The distance between the connecting surface24eof the main pole24and the evanescent light generating surface20bof the core20increases with increasing distance from the medium facing surface60. This makes it possible to prevent the light propagating through the core20from being absorbed in part by the main pole24and to prevent the surface plasmons excited on the plasmon exciting part40afrom being absorbed in part by the main pole24.

Now, the principle of generation of near-field light in the present embodiment and the principle of thermally-assisted magnetic recording using the near-field light will be described in detail. Laser light emitted from a laser diode (not shown) enters the core20. As shown inFIG. 3, the laser light50propagates through the core20toward the medium facing surface60, and reaches the vicinity of the plasmon generator40. In the core20, the laser light50is totally reflected at the evanescent light generating surface20bto generate evanescent light permeating into the interposer21a. In the plasmon generator40, surface plasmons are excited on the plasmon exciting part40athrough coupling with the aforementioned evanescent light. The surface plasmons propagate to the near-field light generating part40g, and the near-field light generating part40ggenerates near-field light based on the surface plasmons.

The near-field light generated from the near-field light generating part40gis projected toward a recording medium, reaches the surface of the recording medium and heats a part of the magnetic recording layer of the recording medium. This lowers the coercivity of the part of the magnetic recording layer. In thermally-assisted magnetic recording, the part of the magnetic recording layer with the lowered coercivity is subjected to a write magnetic field produced by the main pole24for data writing.

The effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. In the present embodiment, the inclined portion20b1, which is part of the evanescent light generating surface20bof the core20, and the inclined portion40a1, which is part of the plasmon exciting part40aof the plasmon generator40, are both inclined relative to the virtual straight line L such that the distance from the virtual straight line L decreases with increasing proximity to the medium facing surface60. This allows a larger amount of the laser light50propagating through the core20to reach the evanescent light generating surface20bthan in the case where the evanescent light generating surface20bincludes only the horizontal portion20b2and the plasmon exciting part40aincludes only the horizontal portion40a2, that is, the case where the entire evanescent light generating surface20band the entire plasmon exciting part40aare arranged parallel to the direction of travel of the laser light50propagating through the core20. InFIG. 1, the arrows drawn within the core20indicate the laser light reaching the inclined portion20b1of the evanescent light generating surface20b. Consequently, according to the present embodiment, it is possible to produce much evanescent light from the evanescent light generating surface20band to thereby excite a lot of surface plasmons on the plasmon generator40.

In order for the above-described effects to be exerted noticeably, each of the angles θ1and θ2needs to be of a certain magnitude, and more specifically, should preferably be 10° or more. On the other hand, if the angles θ1and θ2are excessively great, the laser light50cannot be totally reflected at the inclined portion20b1, so that part of the laser light50will pass through the interposer21ato directly reach the inclined portion40a1. In this case, there will occur the various problems associated with the configuration in which the plasmon generator is directly irradiated with laser light to excite plasmons on the plasmon generator. To avoid this, the angles θ1and θ2should preferably be 35° or less, and more preferably, be 20° or less. In view of the foregoing, the angles θ1and θ2should preferably be in the range of 10° to 35°, and more preferably in the range of 10° to 20°.

In the present embodiment, the plasmon exciting part40ais a surface. This allows a lot of surface plasmons to be excited on the plasmon exciting part40a. Further, the plasmon exciting part40aincludes the width changing portion42a. This allows surface plasmons excited on the plasmon exciting part40ato be concentrated as they propagate to the near-field light generating part40g. Consequently, according to the present embodiment, it is possible to produce near-field light that has a small spot diameter and sufficient intensity.

Now, a method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment will be described. The method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment includes the steps of: forming components of a plurality of thermally-assisted magnetic recording heads, except the substrates1, on a substrate that includes portions to become the substrates1of the plurality of thermally-assisted magnetic recording heads, thereby fabricating a substructure including a plurality pre-head portions aligned in a plurality of rows, the plurality of pre-head portions being intended to become individual thermally-assisted magnetic recording heads later; and forming the plurality of thermally-assisted magnetic recording heads by cutting the substructure to separate the plurality of pre-head portions from each other. In the step of forming the plurality of thermally-assisted magnetic recording heads, the cut surfaces are polished into the medium facing surfaces60.

The method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment will now be described in more detail with attention focused on a single thermally-assisted magnetic recording head. The method of manufacturing the thermally-assisted magnetic recording head forms the insulating layer2, the bottom shield layer3, and the bottom shield gap film4in this order on the substrate1first. Next, the MR element5and two leads (not shown) connected to the MR element5are formed on the bottom shield gap film4. The top shield gap film6is then formed to cover the MR element5and the leads. Next, the top shield layer7, the insulating layer8, the middle shield layer9, and the nonmagnetic layer10are formed in this order on the top shield gap film6.

Reference is now made toFIG. 7AthroughFIG. 15Bto describe the process of forming the yoke layer30after the formation of the nonmagnetic layer10.FIG. 7AthroughFIG. 15Beach show a stack of layers formed in the process of manufacturing the thermally-assisted magnetic recording head. Note that portions located below the return pole layer11are omitted fromFIG. 7AthroughFIG. 15B.FIG. 7AtoFIG. 15Aeach show a cross section that intersects the front end face24aof the main pole24and that is perpendicular to the medium facing surface60and the top surface1aof the substrate1.FIG. 7BtoFIG. 15Beach show a cross section of the stack taken in the position at which the medium facing surface60is to be formed.

FIG. 7AandFIG. 7Bshow a step that follows the formation of the nonmagnetic layer10. In this step, first, the return pole layer11is formed on the nonmagnetic layer10. Next, an insulating layer (not shown) is formed to cover the return pole layer11. The not-shown insulating layer is then polished by, for example, chemical mechanical polishing (hereinafter referred to as CMP), until the return pole layer11is exposed. Next, the insulating layer14is formed over the return pole layer11and the not-shown insulating layer. The insulating layer14is then selectively etched to form therein two openings for exposing the top surface of the return pole layer11. In the positions of these two openings, the shield layer12and the coupling layer13are then formed on the return pole layer11. Next, the coil15is formed on the insulating layer14.

FIG. 8AandFIG. 8Bshow the next step. In this step, first, the insulating layer16is formed over the entire top surface of the stack. The insulating layer16is then polished by, for example, CMP, until the shield layer12, the coupling layer13and the coil15are exposed. Next, although not shown, the first layers of the coupling portions17A and17B are formed on the coupling layer13. Then, the cladding layer18is formed over the entire top surface of the stack. The cladding layer18is then polished by, for example, CMP, until the first layers of the coupling portions17A and17B are exposed.

Next, a dielectric layer20P, which is to later become the core20, is formed over the entire top surface of the stack. The dielectric layer20P is then partially etched by, for example, reactive ion etching (hereinafter referred to as RIE), and thereby patterned. The planar shape (the shape as viewed from above) of the dielectric layer20P patterned is the same as that of the core20. Next, although not shown, the second layers of the coupling portions17A and17B are formed on the first layers of the coupling portions17A and17B.

FIG. 9AandFIG. 9Bshow the next step. In this step, first, the cladding layer19is formed over the entire top surface of the stack. The cladding layer19is then polished by, for example, CMP, until the dielectric layer20P and the second layers of the coupling portions17A and17B are exposed. Then, portions of the dielectric layer20P and the cladding layer19are taper-etched by, for example, RIE or ion beam etching (hereinafter referred to as IBE), so that the dielectric layer20P is provided with the inclined portion20b1. A portion of the top surface of the dielectric layer20P that remains unetched makes the horizontal portion20b2. The dielectric layer20P is thereby made into the core20. Next, the cladding layer21is formed over the entire top surface of the stack. The plasmon generator40is then formed on the cladding layer21. The plasmon generator40is formed by, for example, forming a metal film on the cladding layer21and then patterning the metal film by etching a part thereof.

FIG. 10AandFIG. 10Bshow the next step. In this step, first, the dielectric layer22is formed over the entire top surface of the stack. The dielectric layer22is then etched in part by, for example, IBE, so as to expose the inclined portion40b1of the top surface40bof the plasmon generator40. Next, the dielectric layer23is formed over the entire top surface of the stack as shown inFIG. 11AandFIG. 11B.

FIG. 12AandFIG. 12Bshow the next step. In this step, first, a photoresist mask71is formed on the dielectric layer23. The photoresist mask71is formed by patterning a photoresist layer by photolithography. The photoresist mask71covers a portion of the top surface of the dielectric layer23that is to be in contact with the bottom surface24cof the main pole24to be formed later. The photoresist mask71is preferably shaped to have an undercut as shown inFIG. 12Aso as to be easily removable later. Next, the dielectric layer25is formed on the dielectric layer23. The dielectric layer25has a small thickness in the vicinity of the photoresist mask71. The shapes of the bottom surface24cand the connecting surface24eof the main pole24are thereby determined. The photoresist mask71is then lifted off.

FIG. 13AandFIG. 13Bshow the next step. In this step, first, the cladding layer21and the dielectric layers22,23, and25are selectively etched to form therein two openings for exposing the top surfaces of the second layers of the coupling portions17A and17B. Next, the third layers of the coupling portions17A and17B are formed on the second layers of the coupling portions17A and17B. Then, the main pole24is formed over the dielectric layers23and25, and the coupling layer26is formed over the third layers of the coupling portions17A and17B and the dielectric layer25.

FIG. 14AandFIG. 14Bshow the next step. In this step, first, the dielectric layer27is formed over the entire top surface of the stack. The main pole24, the coupling layer26, and the dielectric layer27are then polished by, for example, CMP, so that the top surfaces of the main pole24, the coupling layer26, and the dielectric layer27become even with each other.

FIG. 15AandFIG. 15Bshow the next step. In this step, first, the coil28is formed on the dielectric layer27. The insulating layer29is then formed to cover the coil28. Next, the yoke layer30is formed over the main pole24, the coupling layer26and the insulating layer29.

The steps to follow the formation of the yoke layer30will now be described with reference toFIG. 3andFIG. 4. First, the protective layer31is formed to cover the yoke layer30. Wiring, terminals, and other components are then formed on the top surface of the protective layer31. When the substructure is completed thus, the substructure is cut to separate the plurality of pre-head portions from each other, followed by the polishing of the medium facing surface60and the fabrication of flying rails etc. This completes the thermally-assisted magnetic recording head.

Second Embodiment

A thermally-assisted magnetic recording head according to a second embodiment of the invention will now be described. First, reference is made toFIG. 16andFIG. 17to describe the differences of the thermally-assisted magnetic recording head according to the present embodiment from the thermally-assisted magnetic recording head according to the first embodiment.FIG. 16is a perspective view showing the main part of the thermally-assisted magnetic recording head.FIG. 17is a cross-sectional view showing the configuration of the thermally-assisted magnetic recording head.

The thermally-assisted magnetic recording head according to the present embodiment has a dielectric layer32disposed on the horizontal portion20b2of the evanescent light generating surface20bof the core20. The dielectric layer32has a front end face, a top surface, and a bottom surface. The front end face is continuous with the inclined portion20b1of the evanescent light generating surface20b. The cladding layer21covers the inclined portion20b1of the evanescent light generating surface20b, and the front end face and the top surface of the dielectric layer32. The dielectric layer32may be made of SiO2or alumina, for example.

The front end face of the dielectric layer32is inclined similarly to the inclined portion20b1of the evanescent light generating surface20b. Specifically, the front end face of the dielectric layer32is inclined relative to the virtual straight line L (seeFIG. 1) mentioned in the description of the first embodiment such that the distance from the virtual straight line L decreases with increasing proximity to the medium facing surface60. The angle that the front end face of the dielectric layer32forms relative to the virtual straight line L may be equal to the angle θ1(seeFIG. 1) that the inclined portion20b1of the evanescent light generating surface20bforms relative to the virtual straight line L.

Further, in the thermally-assisted magnetic recording head according to the present embodiment, the plasmon exciting part40aof the plasmon generator40includes only the inclined portion40a1and does not include the horizontal portion40a2. Consequently, in the present embodiment, the entire plasmon exciting part40ais inclined relative to the virtual straight line L such that the distance from the virtual straight line L decreases with increasing proximity to the medium facing surface60. The top surface40bof the plasmon generator40also includes only the inclined portion40b1and does not include the horizontal portion40b2.

Now, a method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment will be described with reference toFIG. 18AthroughFIG. 24B.FIG. 18AthroughFIG. 24Bare cross-sectional views each showing part of a stack of layers formed in the process of manufacturing the thermally-assisted magnetic recording head. Note that portions located below the return pole layer11are omitted fromFIG. 18AthroughFIG. 24B.FIG. 18AtoFIG. 24Aeach show a cross section that intersects the front end face24aof the main pole24and that is perpendicular to the medium facing surface60and the top surface1aof the substrate1.FIG. 18BtoFIG. 24Beach show a cross section of the stack taken in the position at which the medium facing surface60is to be formed.

The method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment is the same as the method according to the first embodiment up to the step of polishing the cladding layer19.FIG. 18AandFIG. 18Bshow a step that follows the polishing of the cladding layer19. In this step, the dielectric layer32is formed over the entire top surface of the stack.

FIG. 19AandFIG. 19Bshow the next step. In this step, portions of the dielectric layers20P and32and the cladding layer19are taper-etched by, for example, IBE, so that the dielectric layer20P is provided with the inclined portion20b1and the dielectric layer32is provided with the front end face mentioned above. The dielectric layer20P is thereby made into the core20.

FIG. 20AandFIG. 20Bshow the next step. In this step, first, the cladding layer21is formed over the entire top surface of the stack. The plasmon generator40is then formed on the cladding layer21. Next, the dielectric layer22is formed over the entire top surface of the stack. Then, part of the dielectric layer22is etched by, for example, IBE, so that the top surface40b(the inclined portion40b1) of the plasmon generator40is exposed as shown inFIG. 21AandFIG. 21B. Next, the dielectric layer23is formed over the entire top surface of the stack as shown inFIG. 22AandFIG. 22B.

FIG. 23AandFIG. 23Bshow the next step. This step forms the dielectric layer25, the third layers of the coupling portions17A and17B, the main pole24, and the coupling layer26in this order in the same manner as in the first embodiment.

FIG. 24AandFIG. 24Bshow the next step. In this step, first, the dielectric layer27is formed over the entire top surface of the stack. The main pole24, the coupling layer26, and the dielectric layer27are then polished by, for example, CMP, so that the top surfaces of the main pole24, the coupling layer26, and the dielectric layer27become even with each other. The subsequent steps are the same as in the first embodiment.

Third Embodiment

A thermally-assisted magnetic recording head according to a third embodiment of the invention will now be described. First, reference is made toFIG. 25to describe the differences of the thermally-assisted magnetic recording head according to the present embodiment from the thermally-assisted magnetic recording head according to the first embodiment.FIG. 25is a cross-sectional view showing the main part of the thermally-assisted magnetic recording head.

In the thermally-assisted magnetic recording head according to the present embodiment, the inclined portion40b1of the top surface40bof the plasmon generator40forms a greater angle relative to the virtual straight line L than the angle formed by the inclined portion40a1of the plasmon exciting part40arelative to the virtual straight line L. Further, the thickness (the dimension in the Z direction) of the plasmon generator40gradually increases with increasing distance from the medium facing surface60, and then becomes constant.

The thermally-assisted magnetic recording head according to the present embodiment includes a nonmagnetic metal layer33made of a nonmagnetic metal material and disposed on the horizontal portion40b2of the top surface40bof the plasmon generator40, and an insulating layer34made of an insulating material and disposed on the top surface of the nonmagnetic metal layer33. The dielectric layer23is disposed to cover the plasmon generator40, the nonmagnetic metal layer33, the insulating layer34, and the dielectric layer22. The nonmagnetic metal layer33is made of, for example, Ru, NiCr, or NiCu. The insulating layer34is made of alumina, for example.

In the thermally-assisted magnetic recording head according to the present embodiment, the main pole24has a first connecting surface24e1and a second connecting surface24e2in place of the connecting surface24ementioned in the description of the first embodiment. In the main pole24, an end of the first connecting surface24e1is connected to the bottom surface24c, the other end of the first connecting surface24e1is connected to an end of the second connecting surface24e2, and the other end of the second connecting surface24e2is connected to the rear end face24b. The distance from the top surface1aof the substrate1to an arbitrary point on the first connecting surface24e1increases with increasing distance from the arbitrary point to the medium facing surface60. The distance between the first connecting surface24e1and the evanescent light generating surface20bof the core20increases with increasing distance from the medium facing surface60. This makes it possible to prevent the light propagating through the core20from being absorbed in part by the main pole24and to prevent the surface plasmons excited on the plasmon exciting part40afrom being absorbed in part by the main pole24. The second connecting surface24e2extends substantially perpendicularly to the medium facing surface60.

The effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. As the plasmon generator40is reduced in thickness (dimension in the Z direction), the excitation efficiency of surface plasmons is decreased to cause less surface plasmons to be excited. For this reason, the plasmon generator40preferably has a thickness of a certain magnitude. In the present embodiment, part of the plasmon generator40gradually increases in thickness (dimension in the Z direction) with increasing distance from the medium facing surface60. According to the present embodiment, this allows the front end face40eto be small in dimension in the Z direction while allowing the plasmon generator40to be large in thickness in the part thereof away from the medium facing surface60. Consequently, according to the present embodiment, it is possible to produce near-field light having a small spot diameter and sufficient intensity.

Now, a method of manufacturing the thermally-assisted magnetic recording head of the present embodiment will be described briefly with reference toFIG. 26andFIG. 27.FIG. 26andFIG. 27are cross-sectional views each showing part of a stack of layers formed in the process of manufacturing the thermally-assisted magnetic recording head. Note that portions located below the return pole layer11are omitted fromFIG. 26andFIG. 27.FIG. 26andFIG. 27each show a cross section that intersects the front end face of the main pole24and that is perpendicular to the medium facing surface60and the top surface1aof the substrate1.

The method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment is the same as the method according to the first embodiment up to the step of forming the cladding layer21.FIG. 26shows a step that follows the formation of the cladding layer21. In this step, first, a metal film40P, which is to later become the plasmon generator40, is formed on the cladding layer21. The nonmagnetic metal layer33and the insulating layer34are then formed in this order on the metal film40P. Next, the metal film40P, the nonmagnetic metal layer33and the insulating layer34are selectively etched in their respective portions located away from the position at which the medium facing surface60is to be formed. A portion of the top surface of the metal film40P thus etched, the portion being covered with the nonmagnetic metal layer33, is to later become the horizontal portion40b2of the top surface40bof the plasmon generator40. The dielectric layer22is then formed around the metal film40P, the nonmagnetic metal layer33and the insulating layer34.

FIG. 27shows the next step. In this step, the metal film40P is etched by, for example, IBE using the nonmagnetic metal layer33and the insulating layer34as etching masks, so that the metal film40P is provided with the inclined portion40b1of the top surface40b. The metal film40P is thereby made into the plasmon generator40. The subsequent steps are the same as in the first embodiment.

Fourth Embodiment

A thermally-assisted magnetic recording head according to a fourth embodiment of the invention will now be described with reference toFIG. 28.FIG. 28is a cross-sectional view showing the main part of the thermally-assisted magnetic recording head. The thermally-assisted magnetic recording head according to the present embodiment is different from the thermally-assisted magnetic recording head according to the first embodiment in the following respects. In the thermally-assisted magnetic recording head according to the present embodiment, the top surface40bof the plasmon generator40includes a connecting portion40b3in addition to the inclined portion40b1and the horizontal portion40b2. The connecting portion40b3has a front end portion connected to the inclined portion40b1and a rear end portion opposite to the front end portion. In the present embodiment, the horizontal portion40b2is connected to the rear end portion of the connecting portion40b3.

The connecting portion40b3is inclined relative to the virtual straight line L such that the distance from the virtual straight line L decreases with increasing proximity to the medium facing surface60. The connecting portion40b3forms a greater angle relative to the virtual straight line L than the angle formed by the inclined portion40b1relative to the virtual straight line L. Further, in the vicinity of the medium facing surface60, the thickness (the dimension in the Z direction) of the plasmon generator40is generally constant regardless of the distance from the medium facing surface60, whereas in the positions away from the medium facing surface60, the thickness of plasmon generator40gradually increases with increasing distance from the medium facing surface60and then becomes constant.

FIG. 28shows an example in which the connecting portion40b3is located above the horizontal portion40a2of the plasmon exciting part40a. However, the connecting portion40b3may be located above the inclined portion40a1of the plasmon exciting part40a. In this case, the top surface40bmay include a second inclined portion inclined relative to the virtual straight line L, in place of the horizontal portion40b2. The second inclined portion may form the same angle relative to the virtual straight line L as the angle formed by the inclined portion40a1of the plasmon exciting part40arelative to the virtual straight line L. In this case, the plasmon exciting part40aneed not necessarily include the horizontal portion40a2.

In the thermally-assisted magnetic recording head according to the present embodiment, the main pole24has the first connecting surface24e1and the second connecting surface24e2mentioned in the description of the third embodiment, in place of the connecting surface24ementioned in the description of the first embodiment.

The present invention is not limited to the foregoing embodiments, and various modifications may be made thereto. For example, as far as the requirements of the appended claims are met, the shapes and locations of the core of the waveguide, the plasmon generator, and the main pole can be chosen as desired, without being limited to the examples illustrated in the foregoing embodiments.

It is apparent that the present invention can be carried out in various forms and modifications in the light of the foregoing descriptions. Accordingly, within the scope of the following claims and equivalents thereof, the present invention can be carried out in forms other than the foregoing most preferable embodiments.