Thermally-assisted magnetic recording head having inclined main magnetic pole and core

A thermally-assisted magnetic recording head includes a main pole, a waveguide, and a plasmon generator. The waveguide includes a core and a cladding. The main pole and the core are located on the same side in the direction of travel of a recording medium relative to the plasmon generator. The main pole has a first end face located in the medium facing surface, and a second end face opposite to the first end face. The core has a front end face opposed to the second end face of the main pole. The cladding includes an interposition section interposed between the front end face of the core and the second end face of the main pole. The front end face of the core and the second end face of the main pole are inclined with respect 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 to write data on a recording medium with the coercivity thereof lowered by irradiating the recording medium with near-field light.

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 unit including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head unit 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 configured to slightly fly above the surface of a recording medium. The slider has a medium facing surface configured to face the recording medium. The medium facing surface has an air inflow end (a leading end) and an air outflow end (a trailing end).

Here, the side of the positions closer to the leading end relative to a reference position will be referred to as the leading side, and the side of the positions closer to the trailing end relative to the reference position will be referred to as the trailing side. The leading side is the rear side in the direction of travel of the recording medium relative to the slider. The trailing side is the front side in the direction of travel of the recording medium relative to the slider.

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, disadvantageously reduces the thermal stability of magnetization of the magnetic fine particles. To resolve 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 resolve the foregoing problems, there has been proposed a technology 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 the 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 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. Pat. Nos. 8,284,637 B2 and 8,456,968 B1 each disclose a technology in which the surface of the core of the waveguide and the surface of the plasmon generator are arranged to face each other with a gap therebetween, so that evanescent light that occurs from the surface of the core based on the light propagating through the core is used to excite surface plasmons on the plasmon generator to generate near-field light based on the excited surface plasmons.

In a thermally-assisted magnetic recording head that employs a plasmon generator as a source of generation of near-field light, the write head unit includes a coil, a main pole and the plasmon generator. The coil produces a magnetic field corresponding to data to be written on a recording medium. The main pole has an end face located in the medium facing surface. The main pole passes a magnetic flux corresponding to the magnetic field produced by the coil, and produces a write magnetic field from the aforementioned end face. The plasmon generator includes a near-field light generating section located in the medium facing surface. To provide a magnetic recording device with higher linear recording density, it is preferred that the end face of the main pole and the near-field light generating section of the plasmon generator be located close to each other in the medium facing surface.

U.S. Pat. Nos. 8,284,637 B2 and 8,456,968 B1 each disclose a structure in which at least part of the main pole is located between the medium facing surface and the front end face of the core closest to the medium facing surface. This structure allows the end face of the main pole and the near-field light generating section of the plasmon generator to be located close to each other in the medium facing surface.

In a thermally-assisted magnetic recording head, the plasmon generator and the main pole become hot due to heat generated by the plasmon generator. This can cause the plasmon generator to be deformed or broken, and cause the main pole to be oxidized or corroded, thus shortening the life of the thermally-assisted magnetic recording head.

The aforementioned structure disclosed in U.S. Pat. Nos. 8,284,637 B2 and 8,456,968 B1 causes the main pole to rise in temperature due to not only the heat generated by the plasmon generator but also light that emerges from the front end face of the core and enters the main pole. The aforementioned structure thus has the problem that the main pole is particularly susceptible to damage.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermally-assisted magnetic recording head in which the end face of the main pole and the near-field light generating section of the plasmon generator are located close to each other in the medium facing surface, the thermally-assisted magnetic recording head allowing for prevention of damage to the main pole.

A thermally-assisted magnetic recording head of the present invention includes: a medium facing surface configured to face a recording medium; a main pole; a waveguide; and a plasmon generator. The main pole produces a write magnetic field for use to write data on the recording medium. The waveguide includes a core through which light propagates, and a cladding provided around the core. The plasmon generator includes a near-field light generating section located in the medium facing surface. The plasmon generator is configured so that a surface plasmon is excited on the plasmon generator based on the light propagating through the core, and the near-field light generating section generates near-field light based on the surface plasmon.

The main pole and the core are located on the same side in the direction of travel of the recording medium relative to the plasmon generator. The main pole has a first end face located in the medium facing surface, and a second end face located opposite to the first end face. The core has a front end face opposed to the second end face of the main pole. The cladding includes an interposition section interposed between the front end face of the core and the second end face of the main pole.

The front end face of the core is inclined with respect to the medium facing surface such that the distance from the medium facing surface to any point on the front end face decreases with decreasing distance from the point on the front end face to the plasmon generator. The second end face of the main pole is inclined with respect to the medium facing surface such that the distance from the medium facing surface to any point on the second end face decreases with decreasing distance from the point on the second end face to the plasmon generator.

In the thermally-assisted magnetic recording head of the present invention, each of the front end face of the core and the second end face of the main pole may form an inclination angle of 30° to 60° with respect to the medium facing surface.

In the thermally-assisted magnetic recording head of the present invention, the core may have an evanescent light generating surface configured to generate evanescent light based on the light propagating through the core, and the plasmon generator may include a plasmon exciting section located at a predetermined distance from the evanescent light generating surface and facing the evanescent light generating surface. In this case, the plasmon generator is configured so that a surface plasmon is excited on the plasmon exciting section through coupling with the evanescent light generated by the evanescent light generating surface, the surface plasmon propagates to the near-field light generating section, and the near-field light generating section generates near-field light based on the surface plasmon.

The plasmon generator may have an inclined surface located opposite to the plasmon exciting section. The inclined surface is inclined with respect to a direction perpendicular to the medium facing surface such that the distance from the plasmon exciting section to any point on the inclined surface decreases with decreasing distance from the point on the inclined surface to the medium facing surface.

The thermally-assisted magnetic recording head of the present invention may further include a heat sink located on a side of the plasmon generator opposite to the main pole.

The thermally-assisted magnetic recording head may further include a reflection film interposed between the interposition section and the second end face of the main pole.

In the thermally-assisted magnetic recording head of the present invention, the main pole and the core are located on the same side in the direction of travel of the recording medium relative to the plasmon generator. The present invention thus allows the first end face of the main pole and the near-field light generating section of the plasmon generator to be located close to each other in the medium facing surface.

In the present invention, the cladding includes the interposition section interposed between the front end face of the core and the second end face of the main pole. The front end face of the core and the second end face of the main pole are inclined with respect to the medium facing surface. The present invention thus allows for a reduction in the amount of light that emerges from the front end face of the core and enters the main pole, thereby allowing for prevention of damage to the main pole.

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. 3andFIG. 4to describe the configuration of a thermally-assisted magnetic recording head according to a first embodiment of the invention.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.

The thermally-assisted magnetic recording head according to the present embodiment is intended for use in perpendicular magnetic recording, and is incorporated in a slider configured to fly over the surface of a rotating recording medium90. The slider has a medium facing surface80configured to face the recording medium90. When the recording medium90rotates, an airflow passing between the recording medium90and the slider causes a lift to be exerted on the slider. The lift causes the slider to fly over the surface of the recording medium90.

As shown inFIG. 3, the thermally-assisted magnetic recording head has the medium facing surface80. Here, we define X direction, Y direction, and Z direction as follows. The X direction is the direction across the tracks of the recording medium90, i.e., the track width direction. The Y direction is a direction perpendicular to the medium facing surface80. The Z direction is the direction of travel of the recording medium90as 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 substrate1formed of a ceramic material such as aluminum oxide-titanium carbide (Al2O3—TiC) and having a top surface1a; an insulating layer2formed of an insulating material and lying on the top surface1aof the substrate1; a bottom shield layer3formed of a magnetic material and lying on the insulating layer2; and an insulating layer4lying on the insulating layer2and surrounding the bottom shield layer3. The insulating layers2and4are formed of alumina (Al2O3), for example. The Z direction is also a direction perpendicular to the top surface1aof the substrate1.

The thermally-assisted magnetic recording head further includes: a magnetoresistive (MR) element5serving as a read element lying on the bottom shield layer3; an insulating layer6lying on the bottom shield layer3and the insulating layer4and surrounding the MR element5; a top shield layer7formed of a magnetic material and lying on the MR element5and the insulating layer6; and an insulating layer8lying on the insulating layer6and surrounding the top shield layer7. The insulating layers6and8are formed of alumina, for example. The parts from the bottom shield layer3to the top shield layer7constitute a read head unit.

An end of the MR element5is located in the medium facing surface80. The MR element5may be an element formed of a magneto-sensitive film that exhibits a magnetoresistive effect, such as a giant magnetoresistive (GMR) element or a tunneling magnetoresistive (TMR) element. Each of the GMR and TMR elements typically includes a free layer, a pinned layer, a spacer layer located between the free layer and the pinned layer, and an antiferromagnetic layer located on a side of the pinned layer opposite to the spacer layer. The free layer is a ferromagnetic layer whose magnetization direction varies in response to a signal magnetic field. The pinned layer is a ferromagnetic layer whose magnetization direction is pinned. The antiferromagnetic layer is to pin the magnetization direction of the pinned layer by means of exchange coupling with the pinned layer. For GMR elements, the spacer layer is a nonmagnetic conductive layer. For TMR elements, the spacer layer is a tunnel barrier layer.

The GMR element may be of either the current-in-plane (CIF) type in which a current for use in magnetic signal detection 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 for use in magnetic signal detection is fed in a direction generally perpendicular to the plane of the layers constituting the GMR element. When the MR element5is a TMR element or a CPP-type GMR element, the bottom shield layer3and the top shield layer7may also serve as electrodes for feeding a sense current to the MR element5. When the MR element5is a CPP-type GMR element, insulating films are respectively provided between the MR element5and the bottom shield layer3and between the MR element5and the top shield layer7, and two leads are provided between these insulating films in order to feed the sense current to the MR element5.

The thermally-assisted magnetic recording head further includes: a nonmagnetic layer10formed of a nonmagnetic material and lying on the top shield layer7and the insulating layer8; a return pole layer11formed of a magnetic material and lying on the nonmagnetic layer10; and an insulating layer12lying on the nonmagnetic layer10and surrounding the return pole layer11. The return pole layer11has an end face located in the medium facing surface80. The nonmagnetic layer10and the insulating layer12are formed of alumina, for example.

The thermally-assisted magnetic recording head further includes: a shield13lying on a first portion of the top surface of the return pole layer11, the first portion being located near the medium facing surface80; two coupling sections14A and14B lying on two second portions of the top surface of the return pole layer11, the two second portions being located away from the medium facing surface80; and an insulating layer15lying on the insulating layer12and a portion of the top surface of the return pole layer11other than the first and second portions. The shield13and the coupling sections14A and14B are formed of a magnetic material. Each of the coupling sections14A and14B has a first layer lying on the return pole layer11, and a second, a third, and a fourth layer stacked in this order on the first layer. The first layers of the coupling sections14A and14B are embedded in the insulating layer15. The first layer of the coupling section14A and the first layer of the coupling section14B are arranged to be adjacent in the track width direction (the X direction). The insulating layer15is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes: a heat sink16located near the medium facing surface80and lying on the shield13and part of the top surface of the insulating layer15; and an insulating layer17provided around the heat sink16. The heat sink16is formed of a material having a high thermal conductivity. More specifically, the heat sink16is formed of, for example, one of Ru, Cr, Cu, Au, Al, W and Mo, or an alloy composed of two or more of these elements. Alternatively, the heat sink16may be formed of AlN or SiC. The insulating layer17is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes a plasmon generator20lying on the heat sink16, and a dielectric layer25provided around the plasmon generator20. The plasmon generator20is formed of metal. More specifically, the plasmon generator20is formed of, for example, one of Au, Ag, Cu, Al, Pd, Ru, Pt, Rh and Ir, or an alloy composed of two or more of these elements. The dielectric layer25is formed of alumina, for example. The second layers of the coupling sections14A and14B are embedded in the insulating layer17and the dielectric layer25. The shape of the plasmon generator20will be described in detail later.

The heat sink16has the function of dissipating heat generated by the plasmon generator20outwardly from the plasmon generator20. In the present embodiment, in particular, the heat sink16is in contact with the plasmon generator20in the medium facing surface80. This enables the heat sink16to perform its function more effectively.

The thermally-assisted magnetic recording head further includes a waveguide. The waveguide includes a core29through which light propagates, and a cladding provided around the core29. The core29has: a front end face29afacing the medium facing surface80; an evanescent light generating surface29b, which is a bottom surface; a top surface29c; and two side surfaces29dand29econnecting the evanescent light generating surface29band the top surface29c. The side surfaces29dand29eare shown inFIG. 2to be described later. The front end face29ais located at a distance from the medium facing surface80.

The cladding includes cladding layers26,30and33and an interposition section31. The cladding layer26lies on the plasmon generator20and the dielectric layer25. The core29lies on the cladding layer26. The cladding layer30lies on the cladding layer26and covers the side surfaces29dand29eof the core29. The interposition section31covers the front end face29aof the core29. The cladding layer33lies over the top surface29aof the core29and the top surfaces of the cladding layer30and the interposition section31.

The core29is formed 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 illustrated) enters the core29and propagates through the core29. The cladding layers26,30and33and the interposition section31are each formed of a dielectric material that has a refractive index lower than that of the core29. For example, the core29can be formed of tantalum oxide such as Ta2O5, SiON, or niobium oxide. The cladding layers26,30and33and the interposition section31can be formed of alumina or SiO2.

The third layers of the coupling sections14A and14B are embedded in the cladding layers26and30. The third layer of the coupling section14A and the third layer of the coupling section14B are located on opposite sides of the core29in the track width direction (the X direction), each being at a distance from the core29. The thermally-assisted magnetic recording head further includes: a main pole27formed of a magnetic material, lying on the cladding layer26and interposed between the front end face29aof the core29and the medium facing surface80; and a heat sink28lying on the cladding layer26and surrounding the main pole27. The interposition section31is interposed between the main pole27and the core29. The main pole27has a first end face27alocated in the medium facing surface80, a second end face27blocated opposite to the first end face27a, and two side surfaces27cand27d. The side surfaces27cand27dare shown inFIG. 2to be described later. The heat sink28is in contact with the side surfaces27cand27dof the main pole27. The cladding layer30is disposed around the heat sink28. The heat sink28has the function of dissipating heat transferred from the plasmon generator20to the main pole27outwardly from the main pole27. The heat sink28is formed of, for example, the same material as the heat sink16.

The thermally-assisted magnetic recording head further includes a coupling layer32formed of a magnetic material and lying on the main pole27. The coupling layer32has an end face located in the medium facing surface80. The length of the coupling layer32in the Y direction which is perpendicular to the medium facing surface80increases with increasing distance from the main pole27. The coupling layer32and the fourth layers of the coupling sections14A and14B are embedded in the cladding layer33. The top surfaces of the coupling layer32, the cladding layer33, and the fourth layers of the coupling sections14A and14B are even with each other.

The thermally-assisted magnetic recording head further includes: a coupling layer34formed of a magnetic material and lying on the coupling layer32; a coupling layer35formed of a magnetic material and lying on the coupling sections14A and14B and the cladding layer33; and an insulating layer36lying on the cladding layer33and surrounding the coupling layers34and35. The coupling layer34has an end face located in the medium facing surface80. The insulating layer36is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes: a coupling layer37formed of a magnetic material and lying on the coupling layer34; a coupling layer38formed of a magnetic material and lying on the coupling layer35; an insulating layer39lying on the insulating layer36; a coil40lying on the insulating layer39; and an insulating layer41provided around the coupling layers37and38to cover the insulating layer39and the coil40. The coupling layer37has an end face facing toward the medium facing surface80and located at a distance from the medium facing surface80. The top surfaces of the coupling layers37and38and the insulating layer41are even with each other. The coil40is wound around the coupling layer38. The coil40is formed of a conductive material such as copper. The insulating layers39and41are formed of alumina, for example.

The thermally-assisted magnetic recording head further includes: a yoke layer42formed of a magnetic material and lying on the coupling layers37and38and the insulating layer41; and an insulating layer43provided around the yoke layer42. The yoke layer42magnetically couples the coupling layers37and38to each other. The yoke layer42has an end face facing toward the medium facing surface80and located at a distance from the medium facing surface80. The insulating layer43is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes a protective layer44disposed to cover the yoke layer42and the insulating layer43. The protective layer44is formed of alumina, for example.

The parts from the return pole layer11to the yoke layer42constitute a write head unit. The coil40produces a magnetic field corresponding to data to be written on the recording medium90. The shield13, the return pole layer11, the coupling sections14A and14B, the coupling layers35and38, the yoke layer42, the coupling layers37,34and32, and the main pole27form a magnetic path for passing a magnetic flux corresponding to the magnetic field produced by the coil40. The main pole27passes the magnetic flux corresponding to the magnetic field produced by the coil40, and produces a write magnetic field for use to write data on the recording medium90by 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 surface80, the read head unit, and the write head unit. The read head unit and the write head unit are stacked on the substrate1. The write head unit is located on the trailing side, i.e., the front side in the direction of travel of the recording medium90(the Z direction), relative to the read head unit.

The write head unit includes the main pole27, the waveguide, the plasmon generator20, and the heat sink16. The waveguide includes the core29and the cladding. The cladding includes the cladding layers26,30and33and the interposition section31.

The main pole27and the core29are located on the same side in the direction of travel of the recording medium90relative to the plasmon generator20. In the present embodiment, the main pole27and the core29are located on the trailing side, i.e., the front side in the direction of travel of the recording medium90, relative to the plasmon generator20.

The heat sink16is located on a side of the plasmon generator20opposite to the main pole27. In the present embodiment, the heat sink16is located on the leading side, i.e., the rear side in the direction of travel of the recording medium90, relative to the plasmon generator20.

The main pole27and the core29will now be described in more detail with reference toFIG. 1andFIG. 2.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. As previously mentioned, the main pole27has the first end face27a, the second end face27b, and the two side surfaces27cand27d. The core29has the front end face29a, the evanescent light generating surface29b, the top surface29c, and the two side surfaces29dand29e. The front end face29aof the core29is opposed to the second end face27bof the main pole27. The interposition section31is interposed between the front end face29aof the core29and the second end face27bof the main pole27.

The front end face29aof the core29and the second end face27bof the main pole27are both inclined with respect to the medium facing surface80as follows. The front end face29aof the core29is inclined with respect to the medium facing surface80such that the distance from the medium facing surface80to any point on the front end face29adecreases with decreasing distance from the point on the front end face29ato the plasmon generator20. The second end face27bof the main pole27is inclined with respect to the medium facing surface80such that the distance from the medium facing surface80to any point on the second end face27bdecreases with decreasing distance from the point on the second end face27bto the plasmon generator20. An inclination angle θ1formed by the front end face29aof the core29with respect to the medium facing surface80and an inclination angle θ2formed by the second end face27bof the main pole27with respect to the medium facing surface80may be equal. Both of the inclination angles θ1and θ2preferably fall within the range of 30° to 60°. The reason therefor will be described in detail later.

The shape of the plasmon generator20will now be described in detail with reference toFIG. 1andFIG. 2. As shown inFIG. 1andFIG. 2, the plasmon generator20includes a plate section21shaped like a plate, and a main body22located on the plate section21. InFIG. 1andFIG. 2the boundary between the plate section21and the main body22is shown by a dotted line. In the present embodiment, the plate section21covers the entire top surface of the heat sink16. This makes it possible to prevent the light propagating through the core29from being optically obstructed by the heat sink16. The plate section21has a front end face21alocated in the medium facing surface80.

The main body22has a front end face22a, a top surface22b, two side surfaces22cand22d, and a rear end face22e. The front end face22ais located in the medium facing surface80. For example, the main body22is rectangular in cross section parallel to the medium facing surface80. The thickness (the dimension in the Z direction) of the main body22is generally constant regardless of distance from the medium facing surface80.

As shown inFIG. 2, the main body22includes a narrow portion22A and a wide portion22B. The narrow portion22A is located near the medium facing surface80. The wide portion22B is located farther from the medium facing surface80than is the narrow portion22A. The narrow portion22A includes the front end face22a. The width of the narrow portion22A in the track width direction (the X direction) may be constant regardless of distance from the medium facing surface80, or may decrease toward the medium facing surface80. The wide portion22B is located on a side of the narrow portion22A opposite to the front end face22aand is connected to the narrow portion22A. The width of the wide portion22B is equal to that of the narrow portion22A at the boundary between the narrow portion22A and the wide portion22B, and is greater than that of the narrow portion22A in the other positions.

The width (the dimension in the track width direction (the X direction)) of the front end face22ais defined by the width of the narrow portion22A in the medium facing surface80. The width of the front end face22afalls within the range of 5 to 60 nm, for example.

The plasmon generator20has a near-field light generating section20alocated in the medium facing surface80, and a plasmon exciting section20blocated at a predetermined distance from the evanescent light generating surface29band facing the evanescent light generating surface29b. In the present embodiment, the near-field light generating section20ais constituted by a corner defined at the front end face22aof the main body22by intersection of the front end face22aand the top surface22bof the main body22, or constituted by the corner and a portion of the front end face22alocated around the corner. The plasmon exciting section20bis constituted by a portion of the top surface22bof the main body22that is opposed to the evanescent light generating surface29b. The cladding layer26includes a portion interposed between the evanescent light generating surface29band the plasmon exciting section20b.

Now, the principle of generation of near-field light in the present embodiment and the principle of thermally-assisted magnetic recording using near-field light will be described in detail. Laser light emitted from a laser diode (not illustrated) enters the core29. As shown inFIG. 3, the laser light50propagates through the core29toward the medium facing surface80, and reaches the vicinity of the plasmon generator20. The evanescent light generating surface29bof the core29generates evanescent light based on the laser light50propagating through the core29. More specifically, the laser light50is totally reflected at the evanescent light generating surface29b, and the evanescent light generating surface29bthereby generates evanescent light that permeates into the cladding layer26. In the plasmon generator20, surface plasmons are excited on the plasmon exciting section20bthrough coupling with the aforementioned evanescent light. The surface plasmons propagate to the near-field light generating section20a, and the near-field light generating section20agenerates near-field light based on the surface plasmons.

The near-field light generated from the near-field light generating section20ais projected toward the recording medium90, reaches the surface of the recording medium90and heats a part of the magnetic recording layer of the recording medium90. 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 pole27for data writing.

The specific functions and effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. In the present embodiment, the main pole27and the core29are located on the same side in the direction of travel of the recording medium90relative to the plasmon generator20. The present embodiment thus allows the first end face27aof the main pole27and the near-field light generating section20aof the plasmon generator20to be located closer to each other in the medium facing surface80by the height of the plasmon generator20in the medium facing surface80when compared with the case where the core29is located on a side of the plasmon generator20opposite to the main pole27. This makes it possible to increase the linear recording density.

When the core29is located on a side of the plasmon generator20opposite to the main pole27, reducing the thickness of the plasmon generator20would bring the first end face27aof the main pole27and the near-field light generating section20aof the plasmon generator20closer to each other. However, reducing the thickness of the plasmon generator20makes the plasmon generator20smaller in volume and thus more likely to rise in temperature. This consequently makes the plasmon generator20susceptible to damage. In contrast, the present embodiment allows the plasmon generator20to be large in thickness while allowing the first end face27aof the main pole27and the near-field light generating section20aof the plasmon generator20to be located close to each other, Further, according to the present embodiment, the heat sink16can be provided on a side of the plasmon generator20opposite to the main pole27. By virtue of the foregoing, the present embodiment makes it possible to reduce a temperature rise of the plasmon generator20and to thereby prevent damage to the plasmon generator20.

Further, in the present embodiment, the front end face29aof the core29is opposed to the second end face27bof the main pole27. Thus, when light propagating through the core29reaches the front end face29aand emerges therefrom, part of the light may enter the main pole27to cause a temperature rise of the main pole27. If a large amount of light enters the main pole27, the main pole27would get hot and become susceptible to damage. To cope with this, in the present embodiment, the cladding includes the interposition section31interposed between the front end face29aof the core29and the second end face27bof the main pole27. Further, the front end face29aof the core29and the second end face27bof the main pole27are inclined with respect to the medium facing surface80. Thus, according to the present embodiment, at least part of the light propagating through the core29and reaching the front end face29ais reflected to allow a smaller amount of light to emerge from the front end face29aof the core29and enter the main pole27. The present embodiment thereby makes it possible to prevent damage to the main pole27.

Further, in the present embodiment, the heat sink28is provided around the main pole27. The heat sink28prevents part of the light that emerges from the front end face29aof the core29from passing through the surrounding areas of the main pole27and reaching the recording medium90. As a result, the present embodiment allows for improvement of signal-to-noise ratio.

Now, a preferable range of the inclination angle θ1of the front end face29aof the core29will be discussed. An excessively small inclination angle θ1would cause the front end face29aof the core29to have an excessively high light transmittance, thereby causing an excessively large amount of light to emerge from the front end face29aof the core29and enter the main pole27. It is thus preferred that the inclination angle θ1be large to some extent, more specifically, 30° or more.

The inclination angle θ1is equal to the incident angle at which the light propagating through the core29impinges on the front end face29a. When the incident angle is greater than or equal to the critical angle, the light propagating through the core29is totally reflected off the front end face29a. The inclination angle θ1is thus preferably greater than or equal to the critical angle.

On the other hand, an excessively large inclination angle θ1would cause a portion of the core29near the plasmon generator20to be small in volume, thereby making the core29unable to propagate a sufficient amount of light to the vicinity of the plasmon generator20. The inclination angle θ1is thus preferably 60° or smaller.

As will be described in detail later, the main pole27is formed after the front end face29aof the core29is formed. The inclination angle θ2of the second end face27bof the main pole27thus depends on the inclination angle θ1of the front end face29aof the core29. The inclination angle θ2of the second end face27bof the main pole27has a preferable range which is the same as that of the inclination angle θ1.

According to the present embodiment, since the front end face29aof the core29is inclined, the edge of the evanescent light generating surface29bclosest to the medium facing surface80and the end of the plasmon exciting section20bclosest to the medium facing surface80can be at a smaller distance from the medium facing surface80than in the case where the front end face29aof the core29is parallel to the medium facing surface80. This makes it possible to excite surface plasmons near the near-field light generating section20alocated in the medium facing surface80and to propagate the excited surface plasmons to the near-field light generating surface20aover a small distance. As a result, it becomes possible to generate near-field light with efficiency.

A manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment will now be described with reference toFIG. 3andFIG. 4. The manufacturing method for the thermally-assisted magnetic recording head includes the steps of: forming components of a plurality of thermally-assisted magnetic recording heads, except the substrates1, on a wafer that includes portions to become the substrates1of the plurality of thermally-assisted magnetic recording heads, thereby fabricating a substructure including a plurality of pre-head portions arranged in rows, the plurality of pre-head portions becoming individual thermally-assisted magnetic recording heads later; and cutting the substructure to separate the plurality of pre-head portions from each other and forming the medium facing surface80for each of the plurality of pre-head portions (this step will be referred to as the step of forming the medium facing surface80). A plurality of thermally-assisted magnetic recording heads are produced in this manner.

The manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment will be described in more detail below with attention focused on a single thermally-assisted magnetic recording head. The manufacturing method for the thermally-assisted magnetic recording head starts with forming the insulating layer2on the substrate1. Then, the bottom shield layer3is formed on the insulating layer2. Next, the insulating layer4is formed to cover the bottom shield layer3. The insulating layer4is then polished by, for example, chemical mechanical polishing (hereinafter referred to as CMP), until the bottom shield layer3is exposed. Next, the MR element5and the insulating layer6are formed on the bottom shield layer3and the insulating layer4. The top shield layer7is then formed on the MR element5and the insulating layer6. Next, the insulating layer8is formed to cover the top shield layer7. The insulating layer8is then polished by, for example, CMP, until the top shield layer7is exposed.

Next, the nonmagnetic layer10is formed on the top shield layer7and the insulating layer8. The return pole layer11is then formed on the nonmagnetic layer10. Next, the insulating layer12is formed to cover the return pole layer11. The insulating layer12is then polished by, for example, CMP, until the return pole layer11is exposed. The shield13and the first layers of the coupling sections14A and14B are then formed on the return pole layer11. Next, the insulating layer15is formed over the entire top surface of the stack. The insulating layer15is then polished by, for example, CMP, until the shield13and the first layers of the coupling sections14A and14B are exposed.

Next, the heat sink16is formed on the shield13and the insulating layer15. Then, the insulating layer17is formed to cover the heat sink16. The insulating layer17is then polished by, for example, CMP, until the heat sink16is exposed. Next, an initial plasmon generator is formed on the heat sink16. The initial plasmon generator is then selectively etched by, for example, ion beam etching (hereinafter referred to as IBE) or reactive ion etching (hereinafter referred to as RIE), or IBE and RIE in combination, so as to make the initial plasmon generator into the plasmon generator20. More specifically, part of the initial plasmon generator is etched to provide the initial plasmon generator with the main body22(seeFIG. 1andFIG. 2). This etching process is stopped before the part of the initial plasmon generator being etched is completely removed. It is thereby possible to form the plate section21(seeFIG. 1andFIG. 2) having the function described previously.

Next, the insulating layer17is selectively etched to form therein two openings for exposing the top surfaces of the first layers of the coupling sections14A and14B. The second layers of the coupling sections14A and14B are then formed on the first layers of the coupling sections14A and14B, respectively. Next, the dielectric layer25is formed over the entire top surface of the stack. The dielectric layer25is then polished by, for example, CMP, until the plasmon generator20and the second layers of the coupling sections14A and14B are exposed.

Next, the cladding layer26is formed over the entire top surface of the stack. An initial core, which will later become the core29, is then formed on the cladding layer26. The initial core is formed by, for example, first forming a dielectric layer on the cladding layer26and then patterning the dielectric layer into the initial core by IBE or RIE, for example. Then, the cladding layer26is selectively etched to form therein two openings for exposing the top surfaces of the second layers of the coupling sections14A and14B. The third layers of the coupling sections14A and14B are then formed on the second layers of the coupling sections14A and14B, respectively. Next, the cladding layer30is formed over the entire top surface of the stack. The cladding layer30is then polished by, for example, CMP, until the initial core and the third layers of the coupling sections14A and14B are exposed. The top surfaces of the initial core, the third layers of the coupling sections14A and14B, and the cladding layer30are thereby made even with each other.

Next, a part of the initial core in the vicinity of the location at which the medium facing surface80is to be formed is taper-etched by, for example, IBE, so as to provide the initial core with the front end face29aof the core29. This makes the initial core into the core29. Where IBE is employed to etch the initial core, the ion beams are allowed to travel in a direction at an angle with respect to the direction perpendicular to the top surface1aof the substrate1. The inclination angle θ1of the front end face29aof the core29with respect to the medium facing surface80can be adjusted by the angle that the direction of travel of the ion beams forms with respect to the direction perpendicular to the top surface1aof the substrate1. This etching process also etches a portion of the cladding layer30. Next, the interposition section31is formed to cover the front end face29aof the core29. The interposition section31may thereafter be etched into a desired thickness.

Next, the main pole27and the heat sink28are formed. To form the main pole27and the heat sink28, the following first and second methods are conceivable. The first method will now be described. According to the first method, an initial heat sink is first formed on the cladding layer26and the interposition section31. The initial heat sink is then selectively etched by, for example, IBE or RIE, or IBE and RIE in combination, so as to form in the initial heat sink a receiving section for receiving the main pole27. This makes the initial heat sink into the heat sink28. The receiving section is shaped to correspond to the shape of the main pole27. The main pole27is then formed in the receiving section.

The second method will now be described. According to the second method, a seed layer (not illustrated) is first formed on the top surface of the stack. Then, a photoresist mask is formed on the seed layer. The photoresist mask has an opening shaped to correspond to the shape of the main pole27. Using the seed layer as an electrode and a seed, the main pole27is then formed by plating in the opening of the photoresist mask. The photoresist mask is then removed. Next, a portion of the seed layer that is not covered with the main pole27is removed by, for example, IBE, using the main pole27as an etching mask. The heat sink28is then formed around the main pole27.

Steps to follow the formation of the main pole27and the heat sink28will now be described. First, the fourth layers of the coupling sections14A and14B are formed on the third layers of the coupling sections14A and14B, respectively. Next, the cladding layer33is formed over the entire top surface of the stack. The cladding layer33is then polished by, for example, CMP, until the fourth layers of the coupling sections14A and14B are exposed. Then, part of the cladding layer33is etched by, for example, IBE, so as to form in the cladding layer33a receiving section for receiving the coupling layer32. The coupling layer32is then formed in the receiving section. Next, the coupling layer34is formed on the coupling layer32and the cladding layer33, and the coupling layer35is formed on the fourth layers of the coupling sections14A and14B and the cladding layer33. Then, the insulating layer36is formed over the entire top surface of the stack. The insulating layer36is then polished by, for example, CMP, until the coupling layers34and35are exposed.

Next, the insulating layer39is formed over the entire top surface of the stack. The insulating layer39is then selectively etched to form therein an opening for exposing the top surface of the coupling layer34and an opening for exposing the top surface of the coupling layer35. Next, the coupling layer37is formed on the coupling layer34, and the coupling layer38is formed on the coupling layer35. The coil40is then formed on the insulating layer39. Next, the insulating layer41is formed over the entire top surface of the stack. The insulating layer41is then polished by, for example, CMP, until the coupling layers37and38are exposed. Then, the yoke layer42is formed on the coupling layers37and38and the insulating layer41. The insulating layer43is then formed over the entire top surface of the stack. The insulating layer43is then polished by, for example, CMP, until the yoke layer42is exposed. Then, the protective layer44is formed to cover the yoke layer42and the insulating layer43. Wiring, terminals, and other components are then formed on the top surface of the protective layer44. When the substructure is completed thus, the step of forming the medium facing surface80is performed. A protective film for covering the medium facing surface80may be formed thereafter. Being provided with the medium facing surface80, each pre-head portion becomes a thermally-assisted magnetic recording head.

The step of forming the medium facing surface80includes the step of polishing the surface of each pre-head portion that has resulted from cutting the substructure, and the step of forming a rail on the polished surface for allowing the slider to fly.

Second Embodiment

A thermally-assisted magnetic recording head according to a second embodiment of the invention will now be described with reference toFIG. 5.FIG. 5is a cross-sectional view showing the main part of the thermally-assisted magnetic recording head according to the present embodiment.

The thermally-assisted magnetic recording head according to the present embodiment differs from the head according the first embodiment in the following ways. In the present embodiment, the plate section21of the plasmon generator20includes a first portion211formed of a first metal material, and a second portion212formed of a second metal material different from the first metal material. The first portion211is located at a distance from the medium facing surface80. The second portion212includes the front end face21aof the plate section21.

In the present embodiment, the main body22of the plasmon generator20includes a first portion221formed of the first metal material, and a second portion222formed of the second metal material. The first portion221is located at a distance from the medium facing surface80. The second portion222includes the front end face22aof the main body22. InFIG. 5, the boundary between the first portion211of the plate section21and the first portion221of the main body22and the boundary between the second portion212of the plate section21and the second portion222of the main body22are each shown by a dotted line.

The first portion221of the main body22constitutes the principal part of the plasmon generator20. In the present embodiment, the plasmon exciting section20bis constituted by a portion of the top surface22bof the main body22that is included in the first portion221. To excite a lot of surface plasmons on the plasmon generator20and propagate the surface plasmons efficiently, it is thus preferred that the first metal material be a material having a high electrical conductivity. Examples of such a material include Au and an alloy predominantly composed of Au. On the other hand, the second portion212of the plate section21and the second portion222of the main body22are exposed in the medium facing surface80. The second metal material is thus preferably a material having high mechanical strength and high thermal stability. Examples of such a material include Ru and Rh.

The present embodiment makes it possible to prevent the plasmon generator20from being mechanically damaged and broken, and from being deformed due to heat generated by the plasmon generator20, without compromising the function of the plasmon generator20.

A manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment will now be described briefly. The manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment is the same as the manufacturing method according to the first embodiment up to the step of polishing the insulating layer17. The next step in the present embodiment is to form a second metal film on the heat sink16. The second metal film is formed of the second metal material. On the second metal film, a photoresist mask is then formed to cover the location at which the medium facing surface80is to be formed and the vicinity thereof. The second metal film is then etched by, for example, IBE, using the photoresist mask. Next, formed is a first metal film of the first metal material. The photoresist mask is then removed. The first and second metal films are then polished by, for example, CMP, so as to make the top surfaces thereof even with each other. Next, the first and second metal films polished are selectively etched by, for example, IBE or RIB, or IBE and RIE in combination, so that the first and second metal films become the plasmon generator20. This makes the first metal film into the first portion211of the plate section21and the first portion221of the main body22, and makes the second metal film into the second portion212of the plate section21and the second portion222of the main body22. The subsequent steps are the same as those in the first embodiment.

Third Embodiment

A thermally-assisted magnetic recording head according to a third embodiment of the invention will now be described with reference toFIG. 6.FIG. 6is a cross-sectional view showing the main part of the thermally-assisted magnetic recording head according to the present embodiment.

The thermally-assisted magnetic recording head according to the present embodiment differs from the head according to the first embodiment in the following ways. The thermally-assisted magnetic recording head according to the present embodiment includes a reflection film24interposed between the interposition section31and the second end face27bof the main pole27. The reflection film24is formed of, for example, one of Au, Cu, Al and Ag, or an alloy composed of two or more of these elements. The present embodiment makes it possible that the light having emerged from the front end face29aof the core29and passed through the interposition section31is reflected by the reflection film24to achieve a further reduction in the amount of light entering the main pole27. The present embodiment thus allows for more effective prevention of damage to the main pole27.

A manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment will now be described briefly. The manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment is the same as the manufacturing method according to the first embodiment up to the step of forming the interposition section31. The next step in the present embodiment is to form the reflection film24on the top surface of the stack. Then, the reflection film24except the portion thereof lying on the interposition section31is removed by IBE or RIE, or IBE and RIE in combination, for example. The main pole27and the heat sink28are then formed. The subsequent steps are the same as those 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. 7.FIG. 7is a cross-sectional view showing the main part of the thermally-assisted magnetic recording head according to the present embodiment.

The thermally-assisted magnetic recording head according to the present embodiment differs from the head according to the first embodiment in the following ways. The plasmon generator20of the present embodiment has an inclined surface20clocated opposite to the plasmon exciting section20b. The inclined surface20cis inclined with respect to the direction perpendicular to the medium facing surface80such that the distance from the plasmon exciting section20bto any point on the inclined surface20cdecreases with decreasing distance from the point on the inclined surface20cto the medium facing surface80.

Further, in the present embodiment, the front end face21aof the plate section21of the plasmon generator20is located at a distance from the medium facing surface80and inclined with respect to the direction perpendicular to the medium facing surface80. The main body22of the plasmon generator20has a connecting surface22fin addition to the front end face22a, the top surface22b, the side surfaces22cand22dand the rear end face22e. The connecting surface22fconnects the front end face21aof the plate section21and the front end face22aof the main body22, and is inclined with respect to the direction perpendicular to the medium facing surface80. The inclined surface20cof the plasmon generator20is constituted by the front end face21aof the plate section21and the connecting surface22fof the main body22.

The thermally-assisted magnetic recording head according to the present embodiment includes a dielectric layer18interposed between the inclined surface20cof the plasmon generator20and the medium facing surface80. The dielectric layer18is formed of alumina, for example.

In the present embodiment, the front end face22aof the main body22has a smaller area than in the first embodiment. The present embodiment thus allows for generation of near-field light with a smaller spot diameter on the recording medium90, and consequently allows for improvement of recording density.

A manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment will now be described briefly. The manufacturing method for the thermally-assisted magnetic recording head according to the present embodiment is the same as the manufacturing method according to the first embodiment up to the step of forming the insulating layer17. The next step in the present embodiment is to form an initial dielectric layer on the heat sink16and the insulating layer17. Then, the initial dielectric layer is etched by, for example, IBE or RIE, or IBE and RIE in combination, so as to make the initial dielectric layer into the dielectric layer18. Next, an initial plasmon generator is formed on the heat sink16and the dielectric layer18. The subsequent steps are the same as those in 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 main pole27, the core29and the plasmon generator20may be shaped and located in any desired manner, and need not necessarily be as in the respective examples illustrated in the foregoing embodiments.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims and equivalents thereof, the invention may be practiced in other than the foregoing most preferable embodiments.