Thermally-assisted magnetic recording head having a plasmon generator

A return path section includes first and second yoke portions and first, second and third columnar portions. The first and second yoke portions and the first columnar portion are located on the same side in the direction of travel of the recording medium relative to a wave guide core. The second and third columnar portions are located on opposite sides of a plasmon generator and connected to a shield. The first yoke portion connects a main pole to the first columnar portion. The second yoke portion connects the first columnar portion to the second and third columnar portions. A coil is wound around the first columnar portion.

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 in which 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 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 that flies slightly above the surface of a recording medium. The slider has a medium facing surface facing 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 defined as the leading side, and the side of the positions closer to the trailing end relative to the reference position will be defined 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, 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 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. Patent Application Publication No. 2011/0058272 A1 discloses 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.

A thermally-assisted magnetic recording head that employs a plasmon generator as a source of generation of near-field light is configured so that 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 allows a magnetic flux corresponding to the magnetic field produced by the coil to pass, and produces a write magnetic field from the aforementioned end face. The plasmon generator includes a near-field light generating part located in the medium facing surface. For the thermally-assisted magnetic recording head, it is demanded that the end face of the main pole and the near-field light generating part of the plasmon generator be located in close proximity to each other.

To increase the linear recording density of a magnetic recording device, it is effective to use a perpendicular magnetic recording system in which the direction of magnetization of signals to be written on tracks of a recording medium is perpendicular to the plane of the recording medium. It is also effective to increase, on the tracks, the gradient of the change in write magnetic field intensity with respect to the change in position along the direction in which the tracks extend, i.e., the direction along the tracks (this gradient will hereinafter be referred to as the write field intensity gradient). These also apply to a magnetic recording device that employs thermally-assisted magnetic recording.

In order to increase the write field intensity gradient in a magnetic head of the perpendicular magnetic recording system, it is effective to provide a shield that has an end face located in the medium facing surface at a position near the end face of the main pole. U.S. Patent Application Publication No. 2011/0058272 A1 discloses a technology for increasing the write field intensity gradient by providing a bottom shield on the leading side of the main pole, the bottom shield having an end face located in the medium facing surface.

A magnetic head including a shield is typically provided with a return path section for connecting the shield to a portion of the main pole located away from the medium facing surface. One or more spaces are defined between the return path section and the main pole. The coil is provided to pass through the one or more spaces.

Now, consider a thermally-assisted magnetic recording head configured so that the near-field light generating part of the plasmon generator is interposed between the end face of the main pole and the end face of the shield, and the core of the waveguide and the return path section intersect each other without contacting each other. A general approach to precluding the contact between the core and the return path section is to branch a portion of the return path section that intersects the core into two portions so as to detour around the core and then merge the two portions into one, as disclosed in U.S. Patent Application Publication No. 2011/0058272 A1. When this approach is employed, the return path section is formed to include a coupling portion for coupling the two branched portions. The coil is wound around the coupling portion, for example.

In the above-described configuration, the width of the coupling portion in the track width direction is equal to or greater than the distance between the respective outer ends of the two branched portions in the track width direction, thus being comparatively great. The coil should be long in entire length if wound around the coupling portion. In this case, the coil has a high resistance, and consequently a high heating value. This gives rise to a problem that components around the coil expand and as a result, part of the medium facing surface protrudes toward the recording medium and may readily collide with the recording medium. In order to prevent this, the distance between the medium facing surface and the recording medium could be increased. However, this would disadvantageously lead to deterioration in write characteristics such as the overwrite property or to an increase in error rate.

On the other hand, in order to improve the write characteristics in a high frequency band, it is desirable that the main pole, the shield and the return path section should form a magnetic path of reduced length. To achieve this, it is effective to bring the portion of the return path section intersecting the core into closer proximity to the medium facing surface. Here, assume that the coil is wound around the coupling portion of the return path section. In this case, since the coupling portion is comparatively great in width in the track width direction as mentioned above, the coil should include one or more conductor portions located between the coupling portion and the medium facing surface and extending linearly in parallel to the medium facing surface (such one or more conductor portions will hereinafter be referred to as linear conductor portion(s)). Bringing the portion of the return path section intersecting the core into closer proximity to the medium facing surface causes the linear conductor portion(s) to be narrow and long. This in turn causes the coil to be higher in resistance, so that the above-described various problems will become more noticeable. Accordingly, in this case, it is difficult to reduce the length of the magnetic path formed by the main pole, the shield and the return path section.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermally-assisted magnetic recording head including a plasmon generator in which a near-field light generating part of the plasmon generator is located in the medium facing surface at a position between the end face of a main pole and the end face of a shield, the thermally-assisted magnetic recording head exhibiting excellent write characteristics in a high frequency band and being low in coil resistance.

A thermally-assisted magnetic recording head of the present invention includes: a medium facing surface facing a recording medium; a coil producing a magnetic field that corresponds to data to be written on the recording medium; a main pole; a shield formed of a magnetic material; a return path section formed of a magnetic material; a waveguide; and a plasmon generator. The main pole has a first end face located in the medium facing surface. The main pole allows a magnetic flux corresponding to the magnetic field produced by the coil to pass, and produces a write magnetic field for writing data on the recording medium by means of a perpendicular magnetic recording system. The shield has a second end face located in the medium facing surface. The return path section connects the main pole and the shield to each other, and allows a magnetic flux corresponding to the magnetic field produced by the coil to pass. 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 part located in the medium facing surface.

The first end face and the second end face are located at positions that are different from each other in the direction of travel of the recording medium. The near-field light generating part is located between the first end face and the second end face. 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 part generates near-field light based on the surface plasmon.

The return path section includes a first yoke portion, a second yoke portion, a first columnar portion, a second columnar portion, and a third columnar portion. The first yoke portion, the second yoke portion and the first columnar portion are located on the same side in the direction of travel of the recording medium relative to the core. The first columnar portion is located away from the medium facing surface and has a first end and a second end opposite to each other in the direction of travel of the recording medium. The second and third columnar portions are located closer to the medium facing surface than is the first columnar portion. The first yoke portion connects one of the main pole and the shield to the first end of the first columnar portion. The second columnar portion and the third columnar portion are located on opposite sides of the plasmon generator in the track width direction, and connected to the other of the main pole and the shield. The second yoke portion is connected to the second end of the first columnar portion, and connected to the other of the main pole and the shield via the second and third columnar portions. The coil is wound around the first columnar portion.

In the thermally-assisted magnetic recording head of the present invention, the core may have an evanescent light generating surface that generates evanescent light based on the light propagating through the core, and the plasmon generator may include a plasmon exciting part located at a predetermined distance from the evanescent light generating surface and facing the evanescent light generating surface. In this case, in the plasmon generator, a surface plasmon is excited on the plasmon exciting part through coupling with the evanescent light generated by 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 core may have a front end face facing toward the medium facing surface. In this case, the front end face may be located between the first end face and the second end face in the direction of travel of the recording medium.

Where the core has the front end face facing toward the medium facing surface, the front end face may have a first edge and a second edge opposite to each other in the direction of travel of the recording medium. The first edge is located closer to the near-field light generating part than is the second edge. When the front end face is divided into two regions: a first region extending from the midpoint position between the first edge and the second edge to the first edge; and a second region extending from the midpoint position to the second edge, the shield may overlap only the first region of the front end face when viewed in a direction perpendicular to the medium facing surface. In this case, the second and third columnar portions are connected to the shield.

Where the shield overlaps only the first region of the front end face when viewed in the direction perpendicular to the medium facing surface and the second and third columnar portions are connected to the shield, the shield may include a first non-overlapping portion and a second non-overlapping portion that are located on opposite sides of the front end face of the core in the track width direction when viewed in the direction perpendicular to the medium facing surface. In this case, the second columnar portion is connected to the first non-overlapping portion, and the third columnar portion is connected to the second non-overlapping portion.

Where the shield overlaps only the first region of the front end face when viewed in the direction perpendicular to the medium facing surface and the second and third columnar portions are connected to the shield, the first end face and the second end face may be at a distance of 50 to 300 nm from each other.

In the thermally-assisted magnetic recording head of the present invention, the first end face may be located on the front side in the direction of travel of the recording medium relative to the near-field light generating part, and the first yoke portion, the second yoke portion and the first columnar portion may be located on the front side in the direction of travel of the recording medium relative to the core. In this case, the first yoke portion may connect the main pole to the first end of the first columnar portion. In addition, the second columnar portion and the third columnar portion may be connected to the shield, and the second yoke portion may be connected to the shield via the second and third columnar portions.

In the thermally-assisted magnetic recording head of the present invention, the first end face may be located on the front side in the direction of travel of the recording medium relative to the near-field light generating part, and the first yoke portion, the second yoke portion and the first columnar portion may be located on the rear side in the direction of travel of the recording medium relative to the core. In this case, the first yoke portion may connect the shield to the first end of the first columnar portion. In addition, the second columnar portion and the third columnar portion may be connected to the main pole, and the second yoke portion may be connected to the main pole via the second and third columnar portions.

In the thermally-assisted magnetic recording head of the present invention, the first yoke portion, the second yoke portion and the first columnar portion are located on the same side in the direction of travel of the recording medium relative to the core, and the coil is wound around the first columnar portion. These features of the present invention make it possible to reduce the entire length of the coil while reducing the length of the magnetic path formed by the main pole, the shield and the return path section. The present invention thus provides a thermally-assisted magnetic recording head including a plasmon generator in which the near-field light generating part of the plasmon generator is located in the medium facing surface at a position between the end face of the main pole and the end face of the shield, the thermally-assisted magnetic recording head exhibiting excellent write characteristics in a high frequency band and being low in coil resistance.

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. 5to describe the configuration of a thermally-assisted magnetic recording head according to a first embodiment of the invention.FIG. 1is a perspective view showing the main part of the thermally-assisted magnetic recording head.FIG. 2is a perspective view showing a part ofFIG. 1.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 coil of the present embodiment.

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 rotating recording medium. 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 surface60facing a recording medium80. 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 medium80, 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 medium80as 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 such as alumina (Al2O3) and disposed on the top surface1aof the substrate1; a bottom shield layer3formed 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 illustrated) connected to the MR element5; a top shield gap film6which is an insulating film disposed on the MR element5; and a top shield layer7formed 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 medium80. The MR element5may be an element formed 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 unit. The thermally-assisted magnetic recording head further includes an insulating layer8disposed on the top shield layer7, a middle shield layer9formed of a magnetic material and disposed on the insulating layer8, and a nonmagnetic layer10formed of a nonmagnetic material and disposed on the middle shield layer9. The insulating layer8and the nonmagnetic layer10are formed of alumina, for example.

The thermally-assisted magnetic recording head further includes a shield11formed of a magnetic material and disposed on the nonmagnetic layer10, and an insulating layer12disposed on the nonmagnetic layer10and surrounding the shield11. As shown inFIG. 2, the shield11has a second end face11alocated in the medium facing surface60, a rear end face11bopposite to the second end face11a, and a top surface11c. The shield11includes a central portion11A, and further includes a first side portion11B and a second side portion11C located on opposite sides of the central portion11A in the track width direction (the X direction). The length of the central portion11A in the direction perpendicular to the medium facing surface60is constant regardless of position in the track width direction. The maximum length of each of the side portions11B and11C in the direction perpendicular to the medium facing surface60is greater than the length of the central portion11A in that direction. The distance from the medium facing surface60to an arbitrary point on a portion of the rear end face11bof the shield11that is included in the central portion11A decreases with increasing distance from the arbitrary point to the top surface1aof the substrate1. The insulating layer12is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes a waveguide. The waveguide includes a core14through which light propagates, and a cladding provided around the core14. As shown inFIG. 2in particular, the core14has a front end face14afacing toward the medium facing surface60, an evanescent light generating surface14bserving as a top surface, a bottom surface14c, and two side surfaces14dand14e. The front end face14amay be located in the medium facing surface60or at a distance from the medium facing surface60.FIG. 1toFIG. 5show an example in which the front end face14ais located in the medium facing surface60.

The cladding includes cladding layers13,15and16. The cladding layer13lies on the shield11and the insulating layer12. The core14lies on the cladding layer13. The cladding layer15lies on the cladding layer13and surrounds the core14. The cladding layer16is disposed over the evanescent light generating surface14bof the core14and the top surface of the cladding layer15.

The core14is 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 core14and propagates through the core14. The cladding layers13,15and16are each formed of a dielectric material that has a refractive index lower than that of the core14. For example, the core14may be formed of tantalum oxide such as Ta2O5or silicon oxynitride (SiON), whereas the cladding layers13,15and16may be formed of silicon dioxide (SiO2) or alumina.

The thermally-assisted magnetic recording head further includes: a plasmon generator17disposed above the evanescent light generating surface14bof the core14in the vicinity of the medium facing surface60and lying on the cladding layer16; and a dielectric layer18lying on the cladding layer16and surrounding the plasmon generator17. The plasmon generator17is configured to excite surface plasmons on the principle to be described later. The plasmon generator17is formed 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 dielectric layer18is formed of the same material as the cladding layers13,15and16, for example. The shape of the plasmon generator17will be described in detail later.

The thermally-assisted magnetic recording head further includes a nonmagnetic metal layer19disposed on the plasmon generator17and the dielectric layer18, and a dielectric layer20disposed on the dielectric layer18and the nonmagnetic metal layer19. Each of the nonmagnetic metal layer19and the dielectric layer20has an end face facing toward the medium facing surface60and located at a distance from the medium facing surface60. The distance from the medium facing surface60to an arbitrary point on the end face of each of the nonmagnetic metal layer19and the dielectric layer20increases with increasing distance from the arbitrary point to the top surface1aof the substrate1. The nonmagnetic metal layer19functions as a heat sink for dissipating heat generated at the plasmon generator17outward from the plasmon generator17. The nonmagnetic metal layer19is formed of Au, for example. The dielectric layer20is formed of the same material as the cladding layers13,15and16, for example.

The thermally-assisted magnetic recording head further includes an insulating layer21lying on the plasmon generator17, the nonmagnetic metal layer19and the dielectric layers18and20, and a main pole22lying on the insulating layer21such that the plasmon generator17is interposed between the main pole22and the core14. The main pole22has a first end face22alocated in the medium facing surface60. The insulating layer21is formed of the same material as the cladding layers13,15and16, for example. The shape of the main pole22will be described in detail later.

The thermally-assisted magnetic recording head further includes a second columnar portion23, a third columnar portion24and a second yoke portion25each formed of a magnetic material. The second yoke portion25is at a predetermined distance from the main pole22and lies on the insulating layer21. The second yoke portion25has a front end face25afacing toward the medium facing surface60, and a bottom surface25b. As shown inFIG. 1, the front end face25aof the second yoke portion25includes a first portion25a1, and further includes a second portion25a2and a third portion25a3located on opposite sides of the first portion25a1in the track width direction. The first portion25a1is shaped to be recessed such that the track-widthwise center of the first portion25a1is farthest from the medium facing surface60. The first portion25a1is disposed to surround the main pole22. The second and third portions25a2and25a3are located in the medium facing surface60at positions on opposite sides of the first end face22aof the main pole22in the track width direction.

As shown inFIG. 1, the bottom surface25bof the second yoke portion25includes a first portion25b1that is located farther from the medium facing surface60than is the main pole22, and further includes a second portion25b2and a third portion25b3located on opposite sides of the main pole22in the track width direction. The second portion25b2of the bottom surface25bis contiguous with the second portion25a2of the front end face25a. The third portion25b3of the bottom surface25bis contiguous with the third portion25a3of the front end face25a. Each of the second and third portions25b2includes an inclined portion inclined relative to the top surface1aof the substrate1. The distance from the top surface1aof the substrate1to an arbitrary point on the inclined portion increases with increasing distance from the arbitrary point to the medium facing surface60.

The second and third columnar portions23and24are located near the medium facing surface60and lie on opposite sides of the core14and the plasmon generator17in the track width direction. The second and third columnar portions23and24penetrate the cladding layers13,15and16and the dielectric layers18and20, and connect the shield11and the second yoke portion25to each other. Each of the second and third columnar portions23and24has a front end face located in the medium facing surface60, a top surface, and a bottom surface. The bottom surface of the second columnar portion23is in contact with a portion of the top surface11cof the shield11that is included in the first side portion11B. The bottom surface of the third columnar portion24is in contact with a portion of the top surface11cof the shield11that is included in the second side portion11C.

The insulating layer21has a first opening for exposing the top surface of the second columnar portion23and a second opening for exposing the top surface of the third columnar portion24. The inclined portion of the second portion25b2of the bottom surface25bof the second yoke portion25is in contact with the top surface of the second columnar portion23through the first opening of the insulating layer21. The inclined portion of the third portion25b3of the bottom surface25bof the second yoke portion25is in contact with the top surface of the third columnar portion24through the second opening of the insulating layer21. The distance from the top surface1aof the substrate1to an arbitrary point on the top surface of each of the second and third columnar portions23and24increases with increasing distance from the arbitrary point to the medium facing surface60.

The thermally-assisted magnetic recording head further includes an insulating layer26disposed around the main pole22and the second yoke portion25. The insulating layer26is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes a first yoke portion34and a first columnar portion28each formed of a magnetic material. The first yoke portion34includes a first layer34A and a second layer34B. The first layer34A lies on the main pole22. The first columnar portion28lies on the second yoke portion25. The first layer34A has an end face facing toward the medium facing surface60and located at a distance from the medium facing surface60. The first columnar portion28has a first end28aand a second end28bopposite to each other in the direction of travel of the recording medium80. In the present embodiment, the first end28ais an end of the first columnar portion28located on the trailing side or the front side in the direction of travel of the recording medium80, whereas the second end28bis an end of the first columnar portion28located on the leading side or the rear side in the direction of travel of the recording medium80.

The thermally-assisted magnetic recording head further includes a coil29wound around the first columnar portion28. As shown inFIG. 5, the coil29is wound approximately three turns around the first columnar portion28. The coil29is formed of a conductive material such as copper. The shape and location of the coil29will be described in detail later.

The thermally-assisted magnetic recording head further includes an insulating film30isolating the coil29from the first layer34A and the first columnar portion28, an insulating layer31disposed in the space between adjacent turns of the coil29, an insulating layer32disposed around the first layer34A and the coil29, and an insulating layer33lying on the coil29, the insulating film30and the insulating layer31. The insulating film30and the insulating layers31to33are formed of alumina, for example.

The second layer34B of the first yoke portion34lies on the first layer34A, the first columnar portion28and the insulating layer33. The second layer34B has an end face facing toward the medium facing surface60and located at a distance from the medium facing surface60.

As shown inFIG. 5, the thermally-assisted magnetic recording head further includes a lead layer35. The lead layer35is located farther from the medium facing surface60than is the second layer34B of the first yoke portion34and lies on the insulating layer33. The lead layer35is used for energizing the coil29, penetrates the insulating layer33and is electrically connected to the coil29. The lead layer35is formed of a conductive material such as copper.

The thermally-assisted magnetic recording head further includes an insulating layer36disposed around the second layer34B of the first yoke portion34and the lead layer35, and a protective layer37disposed to cover the second layer34B, the lead layer35and the insulating layer36. The insulating layer36and the protective layer37are formed of alumina, for example.

The parts from the shield11to the second layer34B of the first yoke portion34constitute a write head unit. The coil29produces a magnetic field corresponding to data to be written on the recording medium80. The shield11, the second and third columnar portions23and24, the second yoke portion25, the first columnar portion28, the first yoke portion34and the main pole22form a magnetic path for passing a magnetic flux corresponding to the magnetic field produced by the coil29. The main pole22allows the magnetic flux corresponding to the magnetic field produced by the coil29to pass, and produces a write magnetic field for writing data on the recording medium80by 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 unit, and the write head unit. The medium facing surface60faces the recording medium80. 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 medium (the Z direction) relative to the read head unit.

The write head unit includes the coil29, the main pole22, the shield11, the waveguide, and the plasmon generator17. The waveguide includes the core14and the cladding. The cladding includes the cladding layers13,15and16.

As shown inFIG. 3, the write head unit further includes a return path section R connecting the main pole22and the shield11to each other and allowing a magnetic flux that corresponds to the magnetic field produced by the coil29to pass. The return path section R includes the first yoke portion34, the second yoke portion25, the first columnar portion28, the second columnar portion23and the third columnar portion24. The return path section R is formed of magnetic material since the first yoke portion34, the second yoke portion25, the first columnar portion28, the second columnar portion23and the third columnar portion24are all formed of magnetic material.

The main pole22has the first end face22alocated in the medium facing surface60. The shield11has the second end face11alocated in the medium facing surface60. The first end face22aand the second end face11aare located at positions different from each other in the direction of travel of the recording medium80(the Z direction). In the present embodiment, the first end face22ais located on the front side in the direction of travel of the recording medium80relative to the second end face11a.

The core14has the front end face14alocated in the medium facing surface60. The front end face14ais located between the first end face22aand the second end face11ain the direction of travel of the recording medium80.

As shown inFIG. 3, the first yoke portion34, the second yoke portion25and the first columnar portion28are located on the same side in the direction of travel of the recording medium80relative to the core14. In the present embodiment, the first yoke portion34, the second yoke portion25and the first columnar portion28are located on the trailing side or the front side in the direction of travel of the recording medium80relative to the core14. As shown inFIG. 3, the first columnar portion28is located away from the medium facing surface60and has the first end28aand the second end28b. As shown inFIG. 1, the second and third columnar portions23and24are located closer to the medium facing surface60than is the first columnar portion28.

The first yoke portion34connects one of the main pole22and the shield11to the first end28aof the first columnar portion28. In the present embodiment, the first yoke portion34connects particularly the main pole22to the first end28aof the first columnar portion28.

The second columnar portion23and the third columnar portion24are located on opposite sides of the plasmon generator17in the track width direction and connected to the other of the main pole22and the shield11, that is, to the shield11. The second yoke portion25is connected to the second end28bof the first columnar portion28, and connected to the other of the main pole22and the shield11, that is, to the shield11via the second and third columnar portions23and24.

The shield11captures a disturbance magnetic field applied to the thermally-assisted magnetic recording head from the outside thereof. This makes it possible to prevent the disturbance magnetic field from being intensively captured into the main pole22and thereby causing erroneous writing on the recording medium80. The shield11also has the function of capturing a magnetic flux that is produced from the first end face22aof the main pole22and spreads in directions other than the direction perpendicular to the plane of the recording medium80, and thereby preventing the magnetic flux from reaching the recording medium80. It is thereby possible to increase the write field intensity gradient. The shield11and the return path section R also have the function of allowing a magnetic flux that has been produced from the first end face22aof the main pole22and has magnetized the recording medium80to flow back to the main pole22.

The shape and location of the coil29will now be described in detail with reference toFIG. 5. As shown inFIG. 5, the coil29is wound approximately three turns around the first columnar portion28. The coil29includes a coil connection29E electrically connected to the lead layer35, and three conductor portions (hereinafter referred to as linear conductor portions)29A,29B and29C interposed between the first columnar portion28and the medium facing surface60and extending linearly in parallel to the medium facing surface60. The linear conductor portions29A,29B and29C are aligned in this order in the direction perpendicular to the medium facing surface60, the linear conductor portion29A being closest to the medium facing surface60. Each of the linear conductor portions29A to29C has a constant width in the direction perpendicular to the medium facing surface60(the Y direction). InFIG. 5, the positions of opposite ends of each of the linear conductor portions29A to29C in the track width direction (the X direction) are indicated in dotted lines. This also applies to other drawings that show other linear conductor portions.

An example of the shape of the plasmon generator17will now be described with reference toFIG. 2. The plasmon generator17has a plasmon exciting part17aserving as a bottom surface, a top surface17b, a front end face17clocated in the medium facing surface60, a rear end face17dopposite to the front end face17c, and two side surfaces17eand17f. The plasmon exciting part17ais located at a predetermined distance from the evanescent light generating surface14bof the core14and faces the evanescent light generating surface14b. The cladding layer16is interposed between the plasmon exciting part17aand the evanescent light generating surface14b. For example, the plasmon generator17is rectangular in cross section parallel to the medium facing surface60.

The front end face17cincludes a near-field light generating part17glocated at the front extremity of the plasmon exciting part17a. The near-field light generating part17gis located between the first end face22aof the main pole22and the second end face11aof the shield11. In the present embodiment, the first end face22ais located on the front side in the direction of travel of the recording medium80relative to the near-field light generating part17g. The near-field light generating part17ggenerates near-field light on the principle to be described later.

As shown inFIG. 2, the plasmon generator17includes a narrow portion located in the vicinity of the medium facing surface60and a wide portion that is located farther from the medium facing surface60than is the narrow portion. The narrow portion has a front end face located in the medium facing surface60. The front end face of the narrow portion also serves as the front end face17cof the plasmon generator17. The width of the narrow portion in the direction parallel to the medium facing surface60and to the top surface1aof the substrate1(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 portion is located on a side of the narrow portion farther from the front end face17cand is coupled to the narrow portion. The width of the wide portion is the same as that of the narrow portion at the boundary between the narrow portion and the wide portion, and increases with increasing distance from the narrow portion.

The width (the dimension in the track width direction (the X direction)) of the front end face17cis defined by the width of the narrow portion in the medium facing surface60. The width of the front end face17cfalls within the range of 5 to 40 nm, for example. The height (the dimension in the Z direction) of the front end face17cis defined by the height of the narrow portion in the medium facing surface60. The height of the front end face17cfalls within the range of 5 to 40 nm, for example.

An example of the shape of the main pole22will now be described with reference toFIG. 3andFIG. 5. As shown inFIG. 3, the main pole22has the first end face22a, and further has a rear end face22bopposite to the first end face22a, and a bottom surface22c. The bottom surface22cincludes an inclined portion and a flat portion arranged in this order, the inclined portion being closer to the medium facing surface60. The distance from the top surface1aof the substrate1to an arbitrary point on the inclined portion increases with increasing distance from the arbitrary point to the medium facing surface60. The inclined portion is opposed to a portion of the top surface17bof the plasmon generator17with the insulating layer21interposed therebetween. The flat portion extends in a direction substantially perpendicular to the medium facing surface60.

As shown inFIG. 5, the main pole22includes a narrow portion22A and a wide portion22B. The narrow portion22A has an end face located in the medium facing surface60and an end opposite to the end face. The wide portion22B is connected to the end of the narrow portion22A. The wide portion22B is greater than the narrow portion22A in width in the track width direction (the X direction). The width of the narrow portion22A in the track width direction is generally constant regardless of the distance from the medium facing surface60. The width of the wide portion22B in the track width direction is the same as that of the narrow portion22A at the boundary between the narrow portion22A and the wide portion22B, and gradually increases with increasing distance from the medium facing surface60, then becoming constant. The narrow portion22A has a length in the range of, for example, 0 to 0.3 μM in the direction perpendicular to the medium facing surface60. Where this length is 0, the narrow portion22A is not present and thus the wide portion22B has an end face located in the medium facing surface60.

The distance between the bottom surface22cof the main pole22and the evanescent light generating surface14bof the core14increases with increasing distance from the medium facing surface60. This feature of the present embodiment makes it possible to prevent the light propagating through the core14from being absorbed in part by the main pole22and to prevent the surface plasmons excited on the plasmon exciting part17afrom being absorbed in part by the main pole22.

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 core14. As shown inFIG. 3, the laser light50propagates through the core14toward the medium facing surface60, and reaches the vicinity of the plasmon generator17. The evanescent light generating surface14bof the core14generates evanescent light based on the laser light50propagating through the core14. More specifically, the laser light50is totally reflected at the evanescent light generating surface14b, and the evanescent light generating surface14bthereby generates evanescent light that permeates into the cladding layer16. In the plasmon generator17, surface plasmons are excited on the plasmon exciting part17athrough coupling with the aforementioned evanescent light. The surface plasmons propagate to the near-field light generating part17g, and the near-field light generating part17ggenerates near-field light based on the surface plasmons.

The near-field light generated from the near-field light generating part17gis projected toward the recording medium80, reaches the surface of the recording medium80and heats a part of the magnetic recording layer of the recording medium80. 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 pole22for 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 near-field light generating part17gof the plasmon generator17is located between the first end face22aof the main pole22and the second end face11aof the shield11. Part of the core14is located in the vicinity of the plasmon generator17. The core14and the return path section R are configured to intersect each other without contacting each other. More specifically, the second and third columnar portions23and24of the return path section R are located on opposite sides of the core14in the track width direction without contacting the core14.

In the present embodiment, the first yoke portion34, the second yoke portion25and the first columnar portion28of the return path section R are located on the same side in the direction of travel of the recording medium80relative to the core14, and the coil29is wound around the first columnar portion28. The present embodiment allows the first columnar portion28to be small in width in the track width direction regardless of the distance between the respective outer ends of the second and third columnar portions23and24in the track width direction. The present embodiment thus allows the coil29to be small in entire length.

In order to improve the write characteristics in a high frequency band, it is desirable that the magnetic path formed by the main pole22, the shield11and the return path section R be reduced in length. To achieve this, it is effective to bring the first columnar portion28into close proximity to the medium facing surface60. In the present embodiment, the coil29is wound around the first columnar portion28which is small in width in the track width direction. Accordingly, even if the first columnar portion28is brought into close proximity to the medium facing surface60, it is possible to avoid an increase in length of each of the linear conductor portions29A to29C located between the first columnar portion28and the medium facing surface60. The present embodiment thus allows the first columnar portion28to be located close to the medium facing surface60without causing a significant increase in resistance of the coil29. Consequently, the present embodiment makes it possible to reduce the entire length of the coil29while reducing the length of the magnetic path. The present embodiment is thus able to provide a thermally-assisted magnetic recording head that exhibits excellent write characteristics in a high frequency band and has the coil29of a low resistance.

Further, the present embodiment allows the coil29to have a low heating value because of its low resistance. This makes it possible to prevent the problem that components around the coil29may expand to cause part of the medium facing surface60to protrude toward the recording medium80and thus become more likely to collide with the recording medium80. Further, the present embodiment allows for a reduction in the distance between the medium facing surface60and the recording medium80for improvements in write characteristics such as the overwrite property.

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 becoming 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.

Now, with reference toFIG. 6AthroughFIG. 14B, the method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment will be described in more detail with attention focused on a single thermally-assisted magnetic recording head.FIG. 6AthroughFIG. 14Beach show a stack of layers formed in the process of manufacturing the thermally-assisted magnetic recording head.FIG. 6AthroughFIG. 14Bare cross-sectional views each showing part of the stack.FIGS. 6A-14Aeach show a cross section that intersects the first end face22aof the main pole22and that is perpendicular to the medium facing surface60and the top surface1aof the substrate1.FIGS. 6B-14Beach show a cross section of the stack taken at the position at which the medium facing surface60is to be formed.

As shown inFIG. 6AandFIG. 6B, the method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment starts with forming the insulating layer2, the bottom shield layer3and the bottom shield gap film4in this order on the substrate1. Next, the MR element5and two leads (not illustrated) 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 layer7is formed on the top shield gap film6.

FIG. 7AandFIG. 7Bshow the next step. In this step, the insulating layer8, the middle shield layer9and the nonmagnetic layer10are formed in this order on the top shield layer7.

FIG. 8AandFIG. 8Bshow the next step. In this step, first, the shield11is formed on the nonmagnetic layer10. Next, the insulating layer12is formed to cover the shield11. The insulating layer12is then polished by, for example, chemical mechanical polishing (hereinafter referred to as CMP), until the shield11is exposed.

FIG. 9AandFIG. 9Bshow the next step. In this step, first, the cladding layer13is formed on the shield11and the insulating layer12. The core14is then formed on the cladding layer13. Next, the cladding layer15is formed to cover the core14. The cladding layer15is then polished by, for example, CMP, until the core14is exposed.

FIG. 10AandFIG. 10Bshow the next step. In this step, first, the cladding layer16is formed on the core14and the cladding layer15. The plasmon generator17is then formed on the cladding layer16. Next, the dielectric layer18is formed to cover the plasmon generator17. The dielectric layer18is then polished by, for example, CMP, until the plasmon generator17is exposed.

FIG. 11AandFIG. 11Bshow the next step. In this step, first, the cladding layers13,15and16and the dielectric layers18and20are etched by, for example, reactive ion etching or ion beam etching so that two openings for exposing the top surface11cof the shield11are formed on opposite sides of the core14in the track width direction. The second and third columnar portions23and24are then formed in the two openings. The second and third columnar portions23and24are formed such that their respective top surfaces are higher in level than the top surface17bof the plasmon generator17and the top surface of the dielectric layer18. Next, the nonmagnetic metal layer19is formed on the plasmon generator17and the dielectric layer18.

FIG. 12AandFIG. 12Bshow the next step. In this step, first, the dielectric layer20is formed on the dielectric layer18and the nonmagnetic metal layer19. Next, the nonmagnetic metal layer19, the dielectric layer20, the second columnar portion23and the third columnar portion24are taper-etched in part by, for example, ion beam etching so as to provide each of the nonmagnetic metal layer19and the dielectric layer20with the end face mentioned previously, and provide each of the second and third columnar portions23and24with the top surface mentioned previously.

FIG. 13AandFIG. 13Bshow the next step. In this step, first, the insulating layer21is formed over the entire top surface of the stack. The insulating layer21is then etched by, for example, reactive ion etching or ion beam etching so as to provide the insulating layer21with the first and second openings mentioned previously. Next, the main pole22and the second yoke portion25are formed by plating, for example. At this time, the main pole22and the second yoke portion25may be formed of the same magnetic metal material simultaneously.

FIG. 14AandFIG. 14Bshow the next step. In this step, first, the insulating layer26is formed to cover the main pole22and the second yoke portion25. The insulating layer26is then polished by, for example, CMP, until the main pole22and the second yoke portion25are exposed. Next, the first layer34A of the first yoke portion34is formed on the main pole22, and the first columnar portion28is formed on the second yoke portion25. The insulating film30is then formed over the entire top surface of the stack. Then, the coil29and the insulating layer31are formed in this order. Next, the insulating layer32is formed over the entire top surface of the stack. The insulating film30and the insulating layer32are then polished by, for example, CMP, until the first layer34A, the first columnar portion28, the coil29and the insulating layer31are exposed.

Next, the insulating layer33is formed on the coil29, the insulating film30and the insulating layer31. The insulating layer33is then selectively etched to form therein an opening for exposing the coil connection29E (seeFIG. 5) of the coil29. Next, the second layer34B of the first yoke portion34is formed on the first layer34A, the first columnar portion28and the insulating layer33. Further, the lead layer35(seeFIG. 5) is formed on the coil connection29E and the insulating layer33. Next, the insulating layer36is formed to cover the second layer34B and the lead layer35. The insulating layer36is then polished by, for example, CMP, until the second layer34B and the lead layer35are exposed.

Next, the protective layer37is formed to cover the second layer34B, the lead layer35and the insulating layer36. Wiring, terminals, and other components are then formed on the top surface of the protective layer37. When the substructure is completed thus, the substructure is cut to separate the plurality of pre-head portions from each other, and then formation of the medium facing surface60by polishing, fabrication of flying rails, and so on are performed to complete 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 with reference toFIG. 15toFIG. 19.FIG. 15is a perspective view showing the main part of the thermally-assisted magnetic recording head.FIG. 16is a front 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.FIG. 18is a front view showing the medium facing surface of the thermally-assisted magnetic recording head.FIG. 19is a plan view showing a part of the thermally-assisted magnetic recording head.

The configuration of the thermally-assisted magnetic recording head according to the present embodiment differs from that of the head according to the first embodiment in the following ways. The thermally-assisted magnetic recording head according to the present embodiment includes a shield40formed of a magnetic material, in place of the shield11. The shield40is located near the front end face14aof the core14. The insulating layer12is not provided in the present embodiment. The cladding layer13lies on the nonmagnetic layer10.

The connections between the shield40and the return path section R are the same as those between the shield11and the return path section R in the first embodiment. Specifically, the second and third columnar portions23and24of the return path section R are connected to the shield40. The second yoke portion25of the return path section R is connected to the shield40via the second and third columnar portions23and24.

The shapes and locations of the shield40and the core14will now be described in detail with reference toFIG. 15andFIG. 16. The shield40has a second end face40alocated in the medium facing surface60, a rear end face40bopposite to the second end face40a, and a top surface40c. The shield40is shaped to be greater in dimension in the track width direction (the X direction) than in dimension in the direction perpendicular to the top surface1aof the substrate1(the Z direction).

The first end face22aof the main pole22and the second end face40aof the shield40are located at positions different from each other in the direction of travel of the recording medium80(the Z direction). In the present embodiment, in particular, the first end face22ais located on the front side in the direction of travel of the recording medium80relative to the second end face40a. The near-field light generating part17gis located between the first end face22aand the second end face40a. As shown inFIG. 16, the distance between the first end face22aand the second end face40awill be represented by reference letter D. The distance D is preferably in the range of 50 to 300 nm and more preferably in the range of 50 to 100 nm.

As shown inFIG. 16, the front end face14aof the core14includes a first portion14a1located away from the medium facing surface60and a second portion14a2located in the medium facing surface60. In the present embodiment, the second portion14a2is located on the rear side in the direction of travel of the recording medium80relative to the first portion14a1. Further, there is a difference in level between the first portion14a1and the second portion14a2. Note that the whole of the front end face14amay be located away from the medium facing surface60.

As shown inFIG. 16, the front end face14ahas a first end E1and a second end E2opposite to each other in the direction of travel of the recording medium80(the Z direction). The first end E1is located on the front side in the direction of travel of the recording medium80relative to the second end E2. The first end E1is thus located closer to the near-field light generating part17gthan is the second end E2. The first end E1also serves as the front end of the first portion14a1in the direction of travel of the recording medium80. The second end E2also serves as the rear end of the second portion14a2in the direction of travel of the recording medium80.

InFIG. 16, the dotted line indicates the midpoint position between the first, end E1and the second end E2. This midpoint position will hereinafter be represented by reference letter C. Further, the front end face14ais divided into two regions: a first region R1extending from the midpoint position C to the first end E1; and a second region R2extending from the midpoint position C to the second end E2. The first region R1includes the first portion14a1and a part of the second portion14a2. The second region R2includes the remainder of the second portion14a2.

The shield40overlaps only the first region R1of the front end face14aof the core14when viewed in the direction perpendicular to the medium facing surface60(the Y direction). The shield40particularly overlaps only the first portion14a1of the first region R1. A part of the rear end face40bof the shield40is opposed to the first portion14a1. The part of the rear end face40bmay or may not be in contact with the first portion14a1. In the latter case, a part of the cladding may be interposed between the part of the rear end face40band the first portion14a1.

The shield40includes an overlapping portion41which overlaps the first region R1(the first portion14a1) when viewed in the direction perpendicular to the medium facing surface60, and further includes a first non-overlapping portion42and a second non-overlapping portion43located on opposite sides of the overlapping portion41in the track width direction (the X direction). InFIG. 19, the boundaries between the overlapping portion41and the first and second non-overlapping portions42and43are indicated in broken lines. The overlapping portion41includes a first portion41A and a second portion41B located on opposite sides of the track-widthwise center of the first region R1. The first and second portions41A and41B overlap the first region R1(the first portion14a1) when viewed in the direction perpendicular to the medium facing surface60. As shown inFIG. 19, each of the first and second portions41A and41B has a length that is in the direction perpendicular to the medium facing surface60and that increases with increasing distance from the track-widthwise center of the first region R1. The overlapping portion41may include not only the first and second portions41A and41B but also a third portion located between the first portion41A and the second portion41B. The length of the third portion in the direction perpendicular to the medium facing surface60is constant regardless of position in the track width direction.

The first and second non-overlapping portions42and43are located on opposite sides of the front end face14aof the core14in the track width direction when viewed in the direction perpendicular to the medium facing surface60. Thus, the first and second non-overlapping portions42and43do not overlap the front end face14a. The maximum length of each of the first and second non-overlapping portions42and43in the direction perpendicular to the medium facing surface60is greater than the length of the overlapping portion41in that direction. In the present embodiment, the second columnar portion23is connected to the first non-overlapping portion42. More specifically, the second columnar portion23is in contact with a portion of the top surface40cof the shield40that is included in the first non-overlapping portion42. The third columnar portion24is connected to the second non-overlapping portion43. More specifically, the third columnar portion24is in contact with a portion of the top surface40cof the shield40that is included in the second non-overlapping portion43.

The top surface40cof the shield40and the evanescent light generating surface14bof the core14are coplanar. Alternatively, the top surface40cand the evanescent light generating surface14bmay be located at different levels in the direction of travel of the recording medium80(the Z direction). The plasmon exciting part17aof the plasmon generator17is located at a predetermined distance from each of the top surface40cand the evanescent light generating surface14b, and faces the top surface40cand the evanescent light generating surface14b. A part of the cladding layer16is interposed between the plasmon exciting part17aand each of the top surface40cand the evanescent light generating surface14b.

The specific functions and effects of the thermally-assisted magnetic recording head according to the present embodiment will now be described. The shield40of the present embodiment has the same functions as those of the shield11described in the first embodiment section. Specifically, the shield40has the functions of capturing a disturbance magnetic field applied to the thermally-assisted magnetic recording head from the outside thereof; capturing a magnetic flux that is produced from the first end face22aof the main pole22and spreads in directions other than the direction perpendicular to the plane of the recording medium80, and thereby preventing the magnetic flux from reaching the recording medium80; and allowing a magnetic flux that has been produced from the first end face22aof the main pole22and has magnetized the recording medium80to flow back to the main pole22.

In the present embodiment, when viewed in the direction perpendicular to the medium facing surface60, the shield40overlaps only the first region R1of the front end face14aof the core14, the first region R1being located closer to the main pole22than the other region of the front end face14a. The present embodiment thus allows the first end face22aof the main pole22and the second end face40aof the shield40to be located closer to each other than in the first embodiment. More specifically, the present embodiment allows the first end face22aand the second end face40ato be in close proximity to each other easily so that the distance D falls within the range of 50 to 300 nm. Consequently, the present embodiment allows the above-described functions of shield40to be effectively exerted to increase the write field intensity gradient. The lower limit of the distance D (50 nm) is a distance necessary to place the near-field light generating part17gbetween the first end face22aand the second end face40a. To increase the write field intensity gradient, the distance D should be as small as possible. In view of the foregoing, the distance D is preferably in the range of 50 to 300 nm and more preferably in the range of 50 to 100 nm.

In the present embodiment, the near-field light generating part17gof the plasmon generator17is located in the medium facing surface60and lies between the first end face22aand the second end face40a. This allows for producing a write magnetic field of a large write field intensity gradient in the vicinity of the near-field light generating part17g. Consequently, the present embodiment allows for an increase in linear recording density.

If the shield40and the front end face14aof the core14are opposed to each other over a large area, the light50propagating through the core14may pass through the front end face14aand enter the shield40, thereby causing the shield40to be heated and expand. This will result in the problem that the shield40will protrude toward the recording medium80and thus readily collide with the recording medium80. In order to avoid this problem, the distance between the medium facing surface60and the recording medium80could be increased. However, this would lead to deterioration in write characteristics such as the overwrite property or to an increase in error rate. In contrast to this, the present embodiment is configured so that the shield40overlaps only the first region R1of the front end face14awhen viewed in the direction perpendicular to the medium facing surface60. More specifically, the shield40is not present between at least the second region R2of the front end face14aand the medium facing surface60. The present embodiment thus prevents the shield40and the front end face14aof the core14from being opposed to each other over a large area, thereby precluding the aforementioned problem.

To preclude the aforementioned problem with higher reliability, the region of the front end face14athat the shield40overlaps when viewed in the direction perpendicular to the medium facing surface60may be only a region extending from a position that is located closer to the first end E1(not coinciding with the first end E1) than is the midpoint position C to the first end E1.

Further, in the present embodiment, the shield40is shaped to be greater in dimension in the track width direction (the X direction) than in dimension in the direction perpendicular to the top surface1aof the substrate1(the Z direction). Consequently, even though the shield40overlaps only the first region R1of the front end face14a, it is possible to connect the second and third columnar portions23and24to two portions of the shield40that are opposite in the track width direction.

In the present embodiment, the shield40formed of a magnetic metal material is provided on the leading side of the plasmon generator17, particularly in the vicinity of the near-field light generating part17g. Since the top surface40cof the shield40is located close to the plasmon exciting part17aof the plasmon generator17, surface plasmons are excited also on the top surface40c. Then, the electric line of force produced by the surface plasmons on the plasmon exciting part17aand the electric line of force produced by the surface plasmons on the top surface40cof the shield40are coupled to each other in the vicinity of the near-field light generating part17g. This produces a high-density electric line of force in a narrow area in the vicinity of the near-field light generating part17g. The spread of the near-field light generated by the near-field light generating part17gis thereby suppressed. Thus, the shield40of the present embodiment has also the function of suppressing the spread of near-field light. By virtue of this function, the present embodiment allows for a reduction in track width to achieve an increase in recording density.

Further, in the present embodiment, the overlapping portion41of the shield40includes the first and second portions41A and41B, and the length of each of the first and second portions41A and41B in the direction perpendicular to the medium facing surface60increases with increasing distance from the track-widthwise center of the first region R1. These features of the present embodiment make it possible to enhance the aforementioned function of the shield16while preventing magnetic flux from being saturated at some midpoint in the shield40.

A method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment will now be described briefly. The method of manufacturing the thermally-assisted magnetic recording head according to the present embodiment differs from the method according to the first embodiment in that the shield11and the insulating layer12are not formed and the cladding layer13, the core14and the cladding layer15are formed subsequent to forming the nonmagnetic layer10.

In the present embodiment, the following steps are performed after the step of forming the cladding layer15and before the step of forming the cladding layer16. First, a mask having an opening shaped to correspond to the planar shape of the shield40is formed on the top surface of the stack. Using this mask as an etching mask, the core14and the cladding layer15are then etched in part by, for example, ion beam etching. This etching provides the stack with a groove for receiving the shield40which will be formed later, and forms the first portion14a1of the front end face14aof the core14. Next, a magnetic layer that will later become the shield40is formed over the entire top surface of the stack by ion beam deposition, for example. The material for forming this magnetic layer deposits on the aforementioned groove and on the surface of the mask. The deposit on the groove is formed to have a top surface located at a higher level than the evanescent light generating surface14bof the core14. The mask is then lifted off. Next, the top surface of the magnetic layer is slightly polished by, for example, CMP, until it reaches the level of the evanescent light generating surface14b. This makes the magnetic layer into the shield40.

Third Embodiment

A thermally-assisted magnetic recording head according to a third embodiment of the invention will now be described with reference toFIG. 20toFIG. 24.FIG. 20is a perspective view showing the main part of the thermally-assisted magnetic recording head.FIG. 21is a cross-sectional view showing the configuration of the thermally-assisted magnetic recording head.FIG. 22is a front view showing the medium facing surface of the thermally-assisted magnetic recording head.FIG. 23is a plan view showing a coil of the present embodiment.FIG. 24is a plan view showing a part of the thermally-assisted magnetic recording head.

The configuration of the thermally-assisted magnetic recording head according to the present embodiment differs from that of the head according to the first embodiment in the following ways. The thermally-assisted magnetic recording head according to the present embodiment includes a coil48, a shield53and a lead layer55in place of the coil29, the shield11and the lead layer35, respectively, of the first embodiment. The coil48, the shield53and the lead layer55are formed of the same materials as those of the coil29, the shield11and the lead layer35, respectively.

The return path section R of the present embodiment includes a first yoke portion45, a second yoke portion54, a first columnar portion47, a second columnar portion57and a third columnar portion58in place of the first yoke portion34, the second yoke portion25, the first columnar portion28, the second columnar portion23and the third columnar portion24, respectively, of the first embodiment. The first yoke portion45, the second yoke portion54, the first columnar portion47, the second columnar portion57and the third columnar portion58are each formed of a magnetic material.

The first yoke portion45includes a first layer45A and a second layer45B. The first layer45A lies on the nonmagnetic layer10. Both the second layer45B and the first columnar portion47lie on the first layer45A. The second layer45B is located near the medium facing surface60. The first columnar portion47is located farther from the medium facing surface60than is the second layer45B. Each of the first layer45A and the second layer45B has an end face located in the medium facing surface60. The first columnar portion47has a first end47aand a second end47bopposite to each other in the direction of travel of the recording medium80. In the present embodiment, the first end47ais an end of the first columnar portion47located on the leading side or the rear side in the direction of travel of the recording medium80, whereas the second end47bis an end of the first columnar portion47located on the trailing side or the front side in the direction of travel of the recording medium80.

The shield53lies on the second layer45B. The shield53has a second end face53alocated in the medium facing surface60and a rear end face53bopposite to the second end face53a. The distance from the medium facing surface60to an arbitrary point on the rear end face53bof the shield53decreases with increasing distance from the arbitrary point to the top surface1aof the substrate1. As shown inFIG. 24, the shield53includes a central portion, and two side portions located on opposite sides of the central portion in the track width direction (the X direction). The length of the central portion in the direction perpendicular to the medium facing surface60is constant regardless of position in the track width direction. The maximum length of each of the two side portions in the direction perpendicular to the medium facing surface60is greater than the length of the central portion in that direction.

As shown inFIG. 23, the coil48is wound approximately three turns around the first columnar portion47. The coil48includes a coil connection48E electrically connected to the lead layer55, and three linear conductor portions48A,48B and48C interposed between the first columnar portion47and the medium facing surface60and extending linearly in parallel to the medium facing surface60. The linear conductor portions48A,48B and48C are aligned in this order in the direction perpendicular to the medium facing surface60, the linear conductor portion48A being closest to the medium facing surface60. Each of the linear conductor portions48A to48C has a constant width in the direction perpendicular to the medium facing surface60(the Y direction).

The insulating layers12,31,32,33and36and the insulating film30are not provided in the present embodiment. Instead, the thermally-assisted magnetic recording head according to the present embodiment includes a first insulating layer (not illustrated) lying on the nonmagnetic layer10and surrounding the first layer45A, an insulating film49isolating the coil48from the second layer45B and the first columnar portion47, an insulating layer51disposed in the space between adjacent turns of the coil48, a second insulating layer (not illustrated) disposed around the second layer45B and the coil48, an insulating layer52lying on the coil48, the insulating film49and the insulating layer51, and an insulating layer56. The insulating film49, the insulating layers51,52and56, the first insulating layer, and the second insulating layer are formed of alumina, for example.

The second yoke portion54lies on the first columnar portion47and the insulating layer52. As shown inFIG. 24, the lead layer55is located farther from the medium facing surface60than is the second yoke portion54, and lies on the insulating layer52. The lead layer55is used for energizing the coil48, penetrates the insulating layer52and is electrically connected to the coil connection48E of the coil48. The insulating layer56is disposed around the shield53, the second yoke portion54and the lead layer55. The cladding layer13lies on the shield53, the second yoke portion54, the lead layer55and the insulating layer56.

The second and third columnar portions57and58are located closer to the medium facing surface60than is the first columnar portion47, and are present on opposite sides of the core14, the plasmon generator17and the main pole22in the track width direction. The second and third columnar portions57and58penetrate the cladding layers13,15and16, the dielectric layers18and20and the insulating layers21and26, and connect the main pole22and the second yoke portion54to each other. The protective layer37is disposed to cover the main pole22, the second columnar portion57, the third columnar portion58and the insulating layer26.

In the present embodiment, the first end face22aof the main pole22is located on the front side in the direction of travel of the recording medium80relative to the second end face53aof the shield53. The front end face14aof the core14and the near-field light generating part17gof the plasmon generator17are located between the first end face22aand the second end face53ain the direction of travel of the recording medium80.

In the present embodiment, the first yoke portion45, the second yoke portion54and the first columnar portion47are located on the leading side or the rear side in the direction of travel of the recording medium80relative to the core14. The second layer45B of the first yoke portion45and the first end47aof the first columnar portion47are connected to the first layer45A. The shield53is connected to the second layer45B. Thus, in the present embodiment the first yoke portion45connects the shield53to the first end47aof the first columnar portion47. The second columnar portion57and the third columnar portion58are connected to the main pole22. The second yoke portion54is connected to the second end47bof the first columnar portion47, and connected to the main pole22via the second and third columnar portions57and58.

Like the first embodiment, the present embodiment allows the first columnar portion47to be small in width in the track width direction and thereby allows the coil48to be small in entire length. Further, like the first embodiment, the present embodiment allows the linear conductor portions48A to48C of the coil48to be small in length in the track width direction. Consequently, the present embodiment makes it possible to bring the first columnar portion47into close proximity to the medium facing surface60without causing a significant increase in resistance of the coil48.

The present invention is not limited to the foregoing embodiments, and various modifications may be made thereto. For example, in the first embodiment, the second yoke portion25may be connected to the main pole22while the first yoke portion34may be connected to the shield11via the second and third columnar portions23and24. In the second embodiment, the second yoke portion25may be connected to the main pole22while the first yoke portion34may be connected to the shield40via the second and third columnar portions23and24. In the third embodiment, the second yoke portion54may be connected to the shield53while the first yoke portion45may be connected to the main pole22via the second and third columnar portions57and58.

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.