Thermally-assisted magnetic recording head having a light source at least inclined from an opposed-to-medium surface

A thermally-assisted magnetic recording head is provided, in which a light source with a sufficient power is disposed in the element-integration surface to improve mass-productivity. The head comprises, in an element-integration surface of a substrate: a light source; a waveguide for propagating light from the light source; and a magnetic pole for generating write field. Further, the edge along optical axis of the light source is set to be parallel with or inclined from the edge on the opposed-to-medium surface side of the element-integration surface. In the head, since the light source is disposed in the element-integration surface, the construction of the optical system can be completed in the stage of a wafer process. This construction can be relatively facilitated and simplified; thus, mass-productivity in the head manufacturing can be improved. Further, a light source with a sufficient power (cavity length) can be disposed in the element-integration surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a head used for thermally-assisted magnetic recording in which a magnetic recording medium is irradiated with near-field light, thereby anisotropic magnetic field of the medium is lowered, thus data can be written. Further, the present invention relates to a head gimbal assembly (HGA) provided with the head, and to a magnetic recording apparatus provided with the HGA. Furthermore, the present invention relates to a method for manufacturing the head.

2. Description of the Related Art

As the recording density of a magnetic disk apparatus, as represented by a magnetic disk apparatus, becomes higher, further improvement has been required in the performance of a thin-film magnetic head and a magnetic recording medium. As the thin-film magnetic head, a composite-type thin-film magnetic head is widely used, which has a stacked structure of a magnetoresistive (MR) element for reading data and an electromagnetic transducer for writing data.

Whereas, the magnetic recording medium is generally a kind of discontinuous body of magnetic microparticles gathered together, and each of the magnetic microparticles has a single magnetic domain structure. Here, one record bit consists of a plurality of the magnetic microparticles. Therefore, in order to improve the recording density, it is necessary to decrease the size of the magnetic microparticles and reduce irregularity in the boundary of the record bit. However, the decrease in size of the magnetic microparticles raises a problem of degradation in thermal stability of the magnetization due to the decrease in volume.

As a measure against the thermal stability problem, it may be possible to increase the magnetic anisotropy energy Ku of the magnetic microparticles. However, the increase in energy Ku causes the increase in anisotropic magnetic field (coercive force) of the magnetic recording medium. Whereas, write field intensity of the thin-film magnetic head is limited by the amount of saturation magnetic flux density of the soft-magnetic material of which the magnetic core of the head is formed. Therefore, the head cannot write data to the magnetic recording medium when the anisotropic magnetic field of the medium exceeds the write field limit.

Recently, as a method for solving the problem of thermal stability, so-called a thermally-assisted magnetic recording technique is proposed. In the technique, a magnetic recording medium formed of a magnetic material with a large energy Ku is used so as to stabilize the magnetization; anisotropic magnetic field of the medium is reduced by applying heat to a portion of the medium, where data is to be written; just after that, writing is performed by applying write field to the heated portion.

In this thermally-assisted magnetic recording technique, there has been generally used a method in which a magnetic recording medium is heated with irradiation of light, such as near-field light, on the medium. In this case, it is important to form a very minute light spot at a desired position on the magnetic recording medium. However, from the beginning, more significant problem to be solved exists in how the light is to be supplied from a light source to the inside of a head, and specifically, where and how the light source is to be disposed.

As for the supplying of light, for example, U.S. Pat. No. 6,567,373 B1, U.S. Pat. No. 6,795,380 B2 and Japanese Patent Publication No. 2007-200475A disclose a structure in which light is guided to a desired position by using an optical fiber and a reflection means. Further, US Patent Publication No. 2006/0187564 A1 discloses a structure in which a unit having a heatsink and a laser diode is mounted on the back surface of a slider. And US Patent Publication No. 2008/0056073 A1 discloses that a structure, in which a reflection mirror is monolithically integrated into a laser diode element, is mounted on the back surface of a slider. Further, US Patent Publication No. 2005/0213436 A1 discloses a slider structure that is integrated with a semiconductor laser. And Robert E. Rottmayer et al. “Heat-Assisted Magnetic Recording” IEEE TRANSACTIONS ON MAGNETICS, Vol. 42, No. 10, p. 2417-2421 (2006) discloses a configuration in which a diffraction grating is irradiated with the light emitted from a laser unit provided within a drive apparatus.

Furthermore, US Patent Publication No. 2008/0002298 A1 and U.S. Pat. No. 5,946,281 A disclose heads in which a light source is disposed in an element-integration surface of a slider substrate. In these heads, a surface-emitting laser diode, which is easily disposed in the element-integration surface, is used as a light source, and laser light from the surface-emitting laser diode is guided to a desired position by using a diffraction optical element. Conventionally, optical devices, such as a reflection mirror, an optical fiber and a laser diode, have been mounted after a polishing operation in the wafer process of head manufacturing. On the contrary, in these heads, by forming an optical system including the diffraction optical element, the reflection mirror, etc. in the wafer process and further providing the surface-emitting laser diode in the element-integration surface also in the wafer process, the construction of the optical system is completed in the stage of the wafer process, which makes this construction comparatively facilitated and simplified and allows improvement of mass-productivity.

However, in a magnetic recording head in which the surface-emitting laser diode and the diffraction grating are disposed in the element-integration surface as described above, insufficient laser output power in the surface-emitting laser diode and degradation in function of the diffraction optical element due to fluctuation of the wavelength of the laser light is likely to lead to serious problems.

First, as for the insufficient laser output power, the amount of output of near-field light, required for attaining a recording density exceeding 1 Tbits/in2in a magnetic disk apparatus performing the thermally-assisted magnetic recording with use of near-field light, has been approximately 1 mW with a spot diameter of 40 nm or less according to the estimation by the present inventors using simulation and the like. Moreover, the light use efficiency, which we estimated for the overall optical system in an expected head structure, has been about 2%. Therefore, the output power necessary for the laser diode as a light source is estimated to be 50 mW or more. However, a surface-emitting laser diode generally has a short cavity length, and the output power is about a several mW for general use. Therefore, it is difficult for the use of the surface-emitting laser diode to meet such high output power.

Next, as for the degradation in function of the diffraction optical element due to fluctuation of the wavelength of the laser light, a diffraction optical element, such as a diffraction grating, has a function of changing a propagation direction of the light. This function is achieved by using a grating having a distance and arrangement designed based on the wavelength of incident light, and significantly affected by the wavelength of the incident light. Here, since the laser diode mounted on a head is a device formed of semiconductor, its wavelength changes according to the change of surrounding temperature. Specifically, the assumed temperature in the environment where a magnetic disk apparatus is used is, for example, about −5 to 60° C. (degrees centigrade), and accordingly the wavelength may vary, for example, by about 5-10 nm. Thus, when such a diffraction optical element is used, a serious problem may occur such that the function of the diffraction optical element is degraded by the wavelength fluctuation and then the laser light may not reach a desired position.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a thermally-assisted magnetic recording head in which a light source with a sufficient power is disposed in the element-integration surface of a slider substrate to improve mass-productivity; and to provide a head gimbal assembly (HGA) including the head and a magnetic recording apparatus including the HGA; and further to provide a method for manufacturing the head.

Another object of the present invention is to provide a thermally-assisted magnetic recording head in which a light source with a sufficient power is disposed in the element-integration surface of a slider substrate to improve mass-productivity, and nevertheless light can effectively be guided to a desired position on the opposed-to-medium surface side without using a diffraction optical element; and to provide an HGA including the head and a magnetic recording apparatus including the HGA; and further to provide a method for manufacturing the head.

Further, another object of the present invention is to provide a thermally-assisted magnetic recording head in which an edge-emitting laser diode, which can easily provide high output power at low cost, is disposed in the element-integration surface of a slider substrate, and light can effectively be guided to a desired position on the opposed-to-medium surface side; and to provide an HGA including the head and a magnetic recording apparatus including the HGA; and further to provide a method for manufacturing the head.

Some terms used in the specification will be defined before explaining the present invention. In a layered structure or an element structure formed in the element-integration surface of a slider substrate of the magnetic recording head according to the present invention, when viewed from a standard layer or element, a substrate side is defined as “lower” side, and the opposite side as an “upper” side. Further, “X-, Y- and Z-axis directions” are indicated in some figures showing embodiments of the head according to the present invention as needed. Here, Z-axis direction indicates above-described “up-and-low” direction, and +Z side corresponds to a trailing side and −Z side to a leading side. And Y-axis direction indicates a track width direction, and X-axis direction indicates a height direction.

Further, a “side surface” of a waveguide provided within the magnetic recording head is defined as an end surface other than the end surfaces perpendicular to the direction in which light propagates within the waveguide (−X direction), out of all the end surfaces surrounding the waveguide. According to the definition, an “upper surface” and a “lower surface” are one of the “side surfaces”. The “side surface” is a surface on which the propagating light can be totally reflected within the waveguide corresponding to a core.

According to the present invention, a thermally-assisted magnetic recording head is provided, which comprises, in an element-integration surface of a substrate: a light source; a waveguide through which a light generated from the light source propagates; and a magnetic pole for generating write field from its end on an opposed-to-medium surface side. Further in the head, an optical axis of the light source or an edge of the light source in a direction along an optical axis is set to be parallel with an edge on the opposed-to-medium surface side of the element-integration surface, or to be inclined at a predetermined acute angle from the edge on the opposed-to-medium surface side.

In the above-described head, since the light source such as a laser diode is disposed in the element-integration surface of the substrate, the construction of the optical system in the head can be completed in the stage of a wafer process. As a result, this construction can be relatively facilitated and simplified; thus, mass-productivity in the head manufacturing can be improved. Further, the edge of the light source in the direction along the optical axis is parallel with an edge on the opposed-to-medium surface side of the element-integration surface, or is inclined at a predetermined acute angle from the edge on the opposed-to-medium surface side. Therefore, a light source with a sufficient output power (cavity length) can be disposed in the element-integration surface. In the case, the light source is preferably an edge-emitting laser diode with a cavity length of at least 300 μm (micrometers), and also preferably an edge-emitting laser diode with an output power of at least 50 mW (milliwatts).

In the thermally-assisted magnetic recording head according to the present invention, it is preferable that, in the element-integration surface, further provided is a plasmon antenna that excites surface plasmon by receiving the light propagating through the waveguide and generates near-field light from its end on the opposed-to-medium surface side. Further, the plasmon antenna is preferably opposed to an end portion on the opposed-to-medium surface side of the waveguide with a predetermined distance. Furthermore, it is preferable that the plasmon antenna comprises an edge which extends from its portion coupled with the light propagating through the waveguide in a surface plasmon mode to an near-field light generating end surface for generating near-field light; and on which surface plasmon excited by the light propagates. In the case, since near-field light is generated by using a surface plasmon mode, the temperature of the plasmon antenna is substantially reduced during radiating near-field light. This reduction of temperature allows the protrusion of the plasmon antenna toward the magnetic recording medium to be suppressed; thereby favorable thermally-assisted magnetic recording can be achieved.

Further, in the thermally-assisted magnetic recording head according to the present invention, it is preferable that a length of the edge of the light source in the direction along the optical axis is half or more the length of the edge on the opposed-to-medium surface side of the element-integration surface, and the waveguide and the magnetic pole are positioned apart from a centerline that indicates a center of the element-integration surface in a track width direction. Further in this case, it is also preferable that the center of gravity of the light source substantially resides on the centerline. This allows the thermally-assisted magnetic recording head to keep a more stable posture during flying.

Furthermore, in the thermally-assisted magnetic recording head according to the present invention, the waveguide preferably extends in a curve in such a way that a light incident on a light-receiving surface of the waveguide travels forward in a curve and reaches a portion on the opposed-to-medium surface side of the waveguide. And it is also preferable that, in the element-integration surface, further provided is a light-path changing means for changing a traveling direction of the light from the light source to a direction toward the opposed-to-medium surface.

Furthermore, in the thermally-assisted magnetic recording head comprising the plasmon antenna with the edge according to the present invention, it is also preferable that a longitudinal axis of the plasmon antenna is inclined within the element-integration surface from a direction perpendicular to the edge on the opposed-to-medium surface side of the element-integration surface toward a surface including a light-emission center of the light source. By setting an inclination angle to the plasmon antenna as described above, the overall curvature of the traveling direction of the light generated from the light source, which is required in order to couple the light with the plasmon antenna, can be made smaller by the amount of the inclination angle. As a result, the propagation loss of the light can be suppressed. Here, the angle θPWformed between a longitudinal axis of the plasmon antenna and a direction perpendicular to the edge on the opposed-to-medium surface side of the element-integration surface is 0° (degree) or more, and 30° or less.

According to the present invention, a head gimbal assembly (HGA) is further provided, which comprises: a thermally-assisted magnetic recording head as described above; and a suspension supporting the thermally-assisted magnetic recording head.

In the HGA according to the present invention, it is preferable that a photo-detector for measuring an output power of the light source to adjust the output power is provided in the suspension; the light source is an edge-emitting laser diode in which each of two end surfaces positioned opposite to each other includes a light-emission center; and further provided, in the element-integration surface, is a detection-waveguide and/or a light-path changing means for detection, used for guiding a light generated from an light-emission center on a side opposite to the waveguide to the photo-detector. Further in this case, it is preferable that a through-hole is provided in the suspension; and the photo-detector is provided on the suspension and on a side opposite to the magnetic recording head in such a way to receive, through the through-hole, the light generated from the light-emission center on the side opposite to the waveguide. This light-detecting mechanism enables the feedback adjustment of the output power of the light source. Further, With this adjustment, there can be suppressed the output change of the light source depending on its environment and the output change over time of the light source; thus the intensity of near-field light emitted from the plasmon antenna can be stabilized. As a result, proper heating of the magnetic recording layer of a magnetic disk can be secured.

According to the present invention, a magnetic recording apparatus is further provided, which comprises: at least one head gimbal assembly as described above; at least one magnetic recording medium; and a recording and light-emission control circuit for controlling light-emission operations of the light source and further controlling write operations which the thermally-assisted magnetic recording head performs to the at least one magnetic recording medium.

According to the present invention, a manufacturing method of a thermally-assisted magnetic recording head is further provided, the head comprising: a light source; a waveguide through which a light generated from the light source propagates; and a magnetic pole for generating write field from its end on an opposed-to-medium surface side,

the manufacturing method comprising the step of, during a thin-film process to form the waveguide and the magnetic pole in an element-integration surface of a substrate, mounting the light source in the element-integration surface in such a way that an edge of the light source in a direction along an optical axis is parallel with an edge on the opposed-to-medium surface side of the element-integration surface, or is inclined at a predetermined acute angle from the edge on the opposed-to-medium surface side.

In the above-described manufacturing method, since the light source such as a laser diode is disposed in the element-integration surface of the substrate, the construction of the optical system in the head can be completed in the stage of a wafer process. As a result, this construction can be relatively facilitated and simplified; thus, mass-productivity in the head manufacturing can be improved. Further, a thermally-assisted magnetic recording head provided with a light source with a sufficient output power (cavity length) can be manufactured. Further in this manufacturing method, it is preferable that an overcoat layer to cover the waveguide and the magnetic pole is provided in the element-integration surface of the substrate and in a region at least except a position where the light source is to be placed, and then, the light source is placed at the position.

Further objects and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention as illustrated in the accompanying figures. In each figure, the same element as an element shown in other figure is indicated by the same reference numeral. Further, the ratio of dimensions within an element and between elements becomes arbitrary for viewability.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a perspective view schematically illustrating a structure of a major part in one embodiment of a magnetic recording apparatus and a head gimbal assembly (HGA) according to the present invention. Here, in the perspective view of the HGA, the side of the HGA, opposed to the surface of the magnetic recording medium, is presented as the upper side.

A magnetic disk apparatus as a magnetic recording apparatus shown inFIG. 1includes: a plurality of magnetic disks10as magnetic recording media, rotating around a rotational axis of a spindle motor11; an assembly carriage device12provided with a plurality of drive arms14thereon; a head gimbal assembly (HGA)17attached on the top end portion of each drive arm14and provided with a thermally-assisted magnetic recording head21as a thin-film magnetic head; and a recording/reproducing and light-emission control circuit13for controlling write/read operations of the thermally-assisted magnetic recording head21and further for controlling the emission operation of a laser diode40that the thermally-assisted magnetic recording head21includes.

The laser diode40is a light source for emitting laser light used for thermally-assisted magnetic recording. The laser diode40is of end-emitting type in the present embodiment, and is provided in the element-integration surface of a slider substrate that is a base of the thermally-assisted magnetic recording head21. In the present embodiment, the magnetic disk10is designed for perpendicular magnetic recording, and has a structure in which sequentially stacked on a disk substrate is: a soft-magnetic under layer; an intermediate layer; and a magnetic recording layer (perpendicular magnetization layer). The anisotropic magnetic field (coercive force) of the magnetic recording layer is set to be a sufficiently large value for stabilizing the magnetization in room temperature. The assembly carriage device12is a device for positioning the thermally-assisted magnetic recording head21above a track formed on the magnetic recording layer of the magnetic disk10, on which recording bits are aligned. In the apparatus, the drive arms14are stacked in a direction along a pivot bearing axis16and can be angularly swung around the axis16by a voice coil motor (VCM)15. The structure of the magnetic disk apparatus according to the present invention is not limited to that described above. For instance, the number of each of magnetic disks10, drive arms14, HGAs17and thermally-assisted magnetic recording heads21may be one.

Referring also toFIG. 1, a suspension20in the HGA17includes: a load beam200; a flexure201with elasticity fixed to the load beam200; and a base plate202provided on the base portion of the load beam200. Further, on the flexure201, there is provided a wiring member203that is made up of lead conductors and connection pads electrically joined to both ends of the lead conductors. The thermally-assisted magnetic recording head21is fixed to the flexure201, that is, to the top end portion of the suspension20so as to face the surface of each magnetic disk10with a predetermined spacing (flying height). Moreover, one ends of the wiring member203are electrically connected to terminal electrodes of the thermally-assisted magnetic recording head21.

The structure of the suspension20is not limited to the above-described one. An IC chip for driving the head may be mounted midway on the suspension20, though not shown.

FIG. 2shows a perspective view illustrating one embodiment of thermally-assisted magnetic recording head21according to the present invention.

As shown inFIG. 2, a thermally-assisted magnetic recording head21includes: a slider substrate210formed of, for example, AlTiC (Al2O3—TiC), and having an air bearing surface (ABS)2100as an opposed-to-medium surface processed so as to provide an appropriate flying height; a head element32, a waveguide35and a surface plasmon antenna36, which are formed in an element-integration surface2102of the slider substrate210, the surface2102being perpendicular to the ABS2100; an overcoat layer38formed on the element-integration surface2102, so as to cover these elements; and a laser diode40of edge-emitting type, disposed on the element-integration surface2102. The head end surface388, which is a surface of the overcoat layer38opposed to the medium, and the ABS2100constitute the whole opposed-to-medium surface of the thermally-assisted magnetic recording head21.

The head element32is constituted of a magnetoresistive (MR) element33for reading data from the magnetic disk and an electromagnetic transducer34for writing data to the magnetic disk. The waveguide35is an optical path for guiding laser light, which is emitted from the laser diode40, to the head end surface388side. Further, the surface plasmon antenna36converts the laser light (waveguide light) propagating through the waveguide35into near-field light. Here, a part of the waveguide35, the surface plasmon antenna36, and a buffering portion50described later constitute a near-field light generating element.

Furthermore, the thermally-assisted magnetic recording head21includes: a pair of terminal electrodes370exposed in the upper surface of the overcoat layer38and electrically connected to the MR element33; a pair of terminal electrodes371also exposed in the upper surface of the overcoat layer38and electrically connected to the electromagnetic transducer34; and a pair of terminal electrodes410and411also exposed in the upper surface of the overcoat layer38and electrically connected to the laser diode40. These terminal electrodes370,371,410and411are electrically connected to the connection pads of the wiring member203provided on the flexure201(FIG. 1).

One ends of the MR element33, the electromagnetic transducer34, and the surface plasmon antenna36reach the head end surface388as an opposed-to-medium surface. During actual write and read operations, the thermally-assisted magnetic recording head21aerodynamically flies above the surface of the rotating magnetic disk with a predetermined flying height. Thus, the ends of the MR element33and electromagnetic transducer34face the surface of the magnetic recording layer of the magnetic disk with an appropriate magnetic spacing. Then, the MR element33reads data by sensing signal magnetic field from the magnetic recording layer, and the electromagnetic transducer34writes data by applying signal magnetic field to the magnetic recording layer. When writing data, laser light is emitted from the laser diode40disposed in the element-integration surface2102of the head21and propagates through the waveguide35. Then, the laser light (waveguide light) is coupled with the surface plasmon antenna36in a surface plasmon mode, as described in detail later. As a result, surface plasmon is excited on the surface plasmon antenna36. The surface plasmon propagates on a propagation edge provided in the surface plasmon antenna36, which will be detailed later, toward the head end surface388, which causes near-field light to be generated from the end on the head end surface388side of the surface plasmon antenna36. The generated near-field light reaches the surface of the magnetic disk, and heats a portion of the magnetic recording layer of the disk. As a result, the anisotropic magnetic field (coercive force) of the portion is decreased to a value that enables writing; thus the thermally-assisted magnetic recording can be accomplished.

Also according toFIG. 2, the slider substrate210is preferably so-called a femto slider in which the thickness TSL(in X-axis direction) is 230 μm (micrometers), the width WSLin the track width direction (Y-axis direction) is 700 μm, and the length LSL(in Z-axis direction) is 850 μm. The femto slider is generally used as a substrate for thin-film magnetic heads capable of high-density recording, and has the smallest standardized size of all the sliders currently on the market. In this case, the element-integration surface2102of the slider substrate210is a region with the area of 230 μm (TSL)×700 μm (WSL).

The laser diode40is mounted in the element-integration surface2102with such a small area. As the laser diode40, InP base, GaAs base or GaN base diodes can be utilized, which are usually used for communication, optical disk storage, or material analysis. The wavelength λLof the emitted laser light may be, for example, in the range of approximately 375 nm (nanometers) to 1.7 μm. For example, a laser diode of InGaAsP/InP quaternary mixed crystal can be used, in which possible wavelength region is set to be from 1.2 to 1.67 μm. The laser diode40has a multilayered structure including an n-electrode40a, an active layer40e, and a p-electrode40i. On the front and rear cleaved surfaces of the multilayered structure, respectively formed are reflective layers420and421for exciting the oscillation by total reflection. Further, the reflective layer420has an opening in the position of the active layer40eincluding a light-emission center4000. Here, the optical axis of the laser diode40is an axis4000aextending through the active layer40eand the light-emission center4000, in the direction perpendicular to the reflective layer420. Further, in the present embodiment, the laser diode40is fixed to the slider substrate210in such a way that the p-electrode40ibecomes on the side of a base layer380formed on the element-integration surface2102, that is, the p-electrode40ibecomes the bottom. The laser diode40is located in the concave portion389where the overcoat layer38does not exist, and the p-electrode40iis electrically joined to a lead electrode4100of the terminal electrode410, the lead electrode4100being formed on the base layer380.

The width WLDof the laser diode40is, for example, in the range from 150 to 250 μm. The length LLDof the laser diode40corresponds approximately to the cavity length that is a distance between the reflective layers420and421, and is, for example, 600 μm. To obtain sufficient output power, this length LLDis preferably 300 μm or more. Further, the height TLDof the laser diode40is, for example, in the range approximately from 60 to 200 μm.

The laser diode40is disposed in such a way that an edge401in the direction along the optical axis4000awithin the bottom of the laser diode40(an edge in the longitudinal direction of the laser diode40) is parallel with an edge2102aon the head end surface388side of the element-integration surface2102, or is inclined at a predetermined acute angle from the edge2102awithin the element-integration surface2102. This means that the optical axis4000ais set to be parallel with the edge2102aor to be inclined at a predetermined acute angle from the edge2102awithin the element-integration surface2102. In the present embodiment, the edge401(in the longitudinal direction) and the optical axis4000aare parallel with the edge2102aof the element-integration surface2102in the track width direction (in the Y-axis direction). Here, the edge401has a length LLDcorresponding to the cavity length. On the other hand, when the slider substrate210is a femto slider, the length of the edge2102aequals to the width WSL, which is 700 μm. Accordingly, even when the edge401has a length LLDof, for example, 600 μm, the laser diode40does not protrude beyond the element-integration surface2102, and can be disposed in the element-integration surface2102without overlapping with the head element32. In the present embodiment, the installation of the laser diode40corresponds to “horizontal mounting” in which the edge of the laser diode40in the longitudinal direction is directed along the track width direction (Y-axis direction).

The length LLDof the edge401corresponds to the cavity length of the laser diode40, and is preferably set to be at least 300 μm for obtaining sufficient laser output power. Therefore, it is understood that the laser diode40having the sufficient output power can be disposed in the element-integration surface2102without protruding beyond the surface2102and without overlapping with the head element32, by setting the edge401and the edge2102aparallel with each other. Here, one of important problems to be solved in the setting of the laser diode40lies in cooling of the laser diode40during light-emitting operation. In the present embodiment, the laser diode40is mounted on the slider substrate210without protruding beyond the element-integration surface2102, which allows the slider substrate210to function as a heatsink that receives heat from the entire bottom surface of the laser diode40and effectively suppresses excessive temperature rise of the laser diode40.

Here, considering on the necessitated laser output power, the amount of output of near-field light, required for attaining a recording density exceeding 1 Tbits/in2in a magnetic disk apparatus performing the thermally-assisted magnetic recording with use of near-field light, has been approximately 1 mW (milliwatt) with a spot diameter of 40 nm or less according to the estimation by the present inventors using simulation and the like. Moreover, the light use efficiency, which we estimated for the overall optical system, has been about 2%. Therefore, the output power necessary for the laser diode40is estimated to be 50 mW or more. Thus, it is understood that the output power of the laser diode40is preferably at least 50 mW. As disclosed in Tetsuya Yagi, “Trend of High-Power Laser Diodes for Recordable Optical Disc Drive”, The Institute of Electrical Engineers of Japan TRANSACTIONS EIS, Vol. 128, No. 5, p. 692-695 (2008), in order to obtain stable and high output power in a laser diode, it is necessary to avoid deviation from linearity (kink) in an operation current vs. laser output characteristic curve, and improve temperature characteristic. For this reason, it is necessary to set the cavity length sufficiently large. In fact, it has been known that the cavity length has to be at least 300 μm for obtaining stable output power of at least 50 mW.

In the present embodiment, the length LLD(600 μm) of the edge401of the laser diode40is half or more the length (700 μm) of the edge2102aof the element-integration surface2102. While, the head element32, the waveguide35and the surface plasmon antenna36are positioned apart from a centerline2102bthat indicates the center of the element-integration surface2102in the track width direction (Y-axis direction). Here, especially, it is also preferable to use a side-element structure in which the head element32is disposed at the end portion of the element-integration surface2102in the track width direction (Y-axis direction). By arranging the laser diode40, the head element32and the waveguide35in the above-described manner, in the case that the slider substrate210is a femto-slider, there can be used the high-output laser diode40having the length LLD, which corresponds to the cavity length, of 350 μm or more, and, for example, 630 μm or less. Moreover, it is also preferable in this arrangement that the center of gravity of the laser diode40substantially resides on the centerline2102b. This allows the thermally-assisted magnetic recording head21to keep a more stable posture during flying. Here, the head element32and the surface plasmon antenna36may be placed on the centerline2102b. In this case, the laser diode40having the length LLDof the edge401of less than 350 μm is used accordingly.

Referring also toFIG. 2, a terminal electrode410is electrically connected to the p-electrode40i, which is the bottom surface of the laser diode40, with a lead electrode4100. Further, a terminal electrode411is electrically connected to the n-electrode40a, which is the upper surface of the laser diode40. Here, the terminal electrode411and the n-electrode40amay be connected to each other with solder4111by using a solder-ball bonding (SBB) method. There may be used as the solder4111metal a material including, for example, Sn, Pb, Ag, Cu, Zn, Al, Bi, In or the like. These terminal electrodes410and411are electrically connected to connection pads of the wiring member203provided on the flexure201(FIG. 1). When a predetermined voltage is applied to the laser diode40through both electrodes410and411, laser light is emitted from the light-emission center4000of the laser diode40. Here, in the head configuration shown inFIG. 2, it is preferable that the oscillation direction of the electric field of laser light emitted from the laser diode40is perpendicular to a layer surface of the active layer40e(in Z-axis direction). That is, it is preferable that the laser light emitted from the laser diode40has TM-mode polarization. This enables the waveguide light propagating through the waveguide35to be coupled with the surface plasmon antenna36in a surface plasmon mode, as described later.

Further, an electric source provided within the magnetic disk apparatus can be used for driving the laser diode40. In fact, the magnetic disk apparatus usually has an electric source with applying voltage of, for example, approximately 2 to 5 V, which is sufficient for the laser oscillation. The laser diode40preferably has a laser output power of at least 50 mW as described above; even in the case that the amount of electric power consumption of the laser diode40is, for example, in the neighborhood of one hundred mW, the amount can be covered sufficiently by the electric source provided within the magnetic disk apparatus. Further, the laser diode40and terminal electrodes410and411are not limited to the above-described embodiment. For example, as for the setting of the laser diode40, there can be other embodiments than the above-described “horizontal mounting”, which will be explained later. Further, the terminal electrode411can also be connected with the n-electrode40aby using, not the SBB, but a wire bonding method. Furthermore, the laser diode40can be fixed to the slider substrate210with the n-electrode40aas the bottom.

FIG. 3shows a cross-sectional view taken by plane A inFIG. 2, schematically illustrating the configuration of the head element32and its vicinity in the thermally-assisted magnetic recording head21.

As shown inFIG. 3, the MR element33is formed on an insulating layer380made of insulating material such as Al2O3(alumina) or SiO2and stacked on the element-integration surface2102, and includes: an MR multilayer332; and a lower shield layer330and an upper shield layer334which sandwich the MR multilayer332and an insulating layer381therebetween. The upper and lower shield layers334and330prevent the MR multilayer332from receiving external magnetic field as a noise. The upper and lower shield layers334and330are magnetic layers formed of a soft-magnetic material such as NiFe (Permalloy), FeSiAl (Sendust), CoFeNi, CoFe, FeN, FeZrN or CoZrTaCr, or the multilayer of at least two of these materials, with thickness of approximately 0.5 to 3 μm, by using a frame plating method or a sputtering method.

The MR multilayer332is a magneto-sensitive part for detecting signal magnetic field by using MR effect. The MR multilayer332may be, for example: a current-in-plane giant magnetoresistive (CIP-GMR) multilayer that utilizes CIP-GMR effect; a current-perpendicular-to-plane giant magnetoresistive (CPP-GMR) multilayer that utilizes CPP-GMR effect; or a tunnel magnetoresistive (TMR) multilayer that utilizes TMR effect. The MR multilayer332that utilizes any MR effect described above can detect signal magnetic field from the magnetic disk with high sensitivity. In the case that the MR multilayer332is a CPP-GMR multilayer or a TMR multilayer, the upper and lower shield layers334and330act as electrodes. Whereas, in the case that the MR multilayer332is a CIP-GMR multilayer, insulating layers are provided between the MR multilayer332and respective upper and lower shield layers334and330; further, formed are MR lead layers that are electrically connected to the MR multilayer332.

Referring also toFIG. 3, the electromagnetic transducer34is designed for perpendicular magnetic recording, and includes a main magnetic pole layer340, a gap layer341, a write coil layer343, a coil insulating layer344, and a write shield layer345.

The main magnetic pole layer340is provided on an insulating layer384made of insulating material such as Al2O3(alumina), and acts as a magnetic path for converging and guiding magnetic flux toward the magnetic recording layer (perpendicular magnetization layer) of the magnetic disk, the magnetic flux being excited by write current flowing through the write coil layer343. The main magnetic pole layer340has a structure in which a main magnetic pole3400and a main pole body3401are sequentially stacked. The main magnetic pole3400includes: a first main pole portion3400areaching the head end surface388and having a small width WP(FIG. 6) in the track width direction; and a second main pole portion3400blocated on the first main pole portion3400aand at the rear (+X side) of the portion3400a. The small width WPof the first main pole portion3400aenables a fine write magnetic field to be generated, so that the track width can be set to be a very small value adequate for higher recording density. The main magnetic pole3400is formed of a soft-magnetic material with saturation magnetic flux density higher than that of the main pole body3401, which is, for example, an iron alloy containing Fe as a main component, such as FeNi, FeCo, FeCoNi, FeN or FeZrN. The thickness of the first main pole portion3400ais, for example, in the range of approximately 0.1 to 0.8 μM.

The gap layer341forms a gap provided for separating the main magnetic pole layer340from the write shield layer345in the region near the head end surface388. The gap layer341is formed, for example, of non-magnetic insulating material such as Al2O3(alumina), SiO2(silicon dioxide), AlN (aluminum nitride) or diamond-like carbon (DLC), or formed of a non-magnetic conductive material such as Ru. The thickness of the gap layer341determines the distance between the main magnetic pole layer340and the write shield layer345, and is, for example, in the range of approximately 0.01 to 0.5 μm.

The write coil layer343is formed on an insulating layer3421made of insulating material such as Al2O3(alumina), in such a way to pass through in one turn at least between the main magnetic pole layer340and the write shield layer345, and has a spiral structure with a back contact portion3402as a center. The write coil layer343is formed of a conductive material such as Cu (copper). The write coil layer343is covered with a coil insulating layer344that is formed of an insulating material such as a heat-cured photoresist and electrically isolates the write coil layer343from the main magnetic pole layer340and the write shield layer345. The write coil layer343has a monolayer structure in the present embodiment; however, may have a two or more layered structure or a helical coil shape. Further, the number of turns of the write coil layer343is not limited to that shown inFIG. 3, and may be, for example, in the range from two to seven.

The write shield layer345reaches the head end surface388, and acts as a magnetic path for the magnetic flux returning from a soft-magnetic under layer that is provided under the magnetic recording layer (perpendicular magnetization layer) of the magnetic disk. The thickness of the write shield layer345is, for example, approximately 0.5 to 5 μm. Further, the write shield layer345has a trailing shield3450that is a portion opposed to the main magnetic pole layer340. The trailing shield3450also extends to the head end surface388, and is provided for receiving the magnetic flux spreading from the main magnetic pole layer340. The trailing shield3450has a width in the track width direction larger than the width of the main pole body3401as well as the first main pole portion3400a. This trailing shield3450causes the magnetic field gradient between the end portion of the trailing shield3450and the first main pole portion3400ato become steeper. As a result, jitter of signal output becomes smaller, and therefore, error rates during read operations can be reduced. The write shield layer345is formed of a soft-magnetic material; especially, the trailing shield3450is preferably formed of a material with high saturation magnetic flux density such as NiFe (Permalloy) or an iron alloy as the main magnetic pole3400is formed of.

Referring also toFIG. 3, a part on the head end surface388side of the waveguide35and the surface plasmon antenna36are provided between the MR element33and the electromagnetic transducer34, and constitute a near-field light generating element as an optical system within the thermally-assisted magnetic recording head21. Here, the waveguide35extends in a curve from a rear end surface352, that is a light-receiving surface to receive laser light emitted from the laser diode40also disposed in the element-integration surface2102, to the end surface350on the head end surface388side. As a result, the laser light (waveguide light) that enters inside from the rear end surface352and propagates through the waveguide35is curved in traveling direction, and reaches a portion on the head end surface388side of the waveguide35. Further, a portion of the upper surface (side surface) of the waveguide35on the head end surface388side is opposed to a portion of the lower surface (including a propagation edge360(FIG. 5)) of the surface plasmon antenna36with a predetermined distance, and the sandwiched portion between these portions constitutes a buffering portion50having a refractive index lower than that of the waveguide35. The buffering portion50acts for coupling the waveguide light that propagates through the waveguide35with the surface plasmon antenna36in a surface plasmon mode. Here, the buffering portion50may be a portion of an insulating layer384that is a part of the overcoat layer38, or a new layer provided other than the insulating layer384. A detailed description of the waveguide35, the surface plasmon antenna36, and the buffering portion50will be given later with reference toFIG. 5.

Alternatively, a plasmon antenna made of a metal plate piece can be used, instead of the surface plasmon antenna36, to generate near-field light by being irradiated with the waveguide light from the waveguide35. Various other embodiments of surface plasmon antenna or plasmon antenna could be used. In any case, the laser light emitted from the laser diode40disposed in the element-integration surface2102can be coupled with a surface plasmon antenna or a plasmon antenna by using the waveguide35extending in a curve. Further, another alternative without using near-field light generating elements can be applied, in which the magnetic recording layer of a magnetic disk is irradiated directly with laser light emitted from the waveguide35to heat a portion of the magnetic recording layer.

Further, in the present embodiment, an inter-element shield layer39is preferably provided between the MR element33and the electromagnetic transducer34(waveguide35), sandwiched by the insulating layers382and383. The inter-element shield layer39plays a role for shielding the MR element33from the magnetic field generated from the electromagnetic transducer34, and may be formed of a soft-magnetic material. Further, a backing coil portion may be provided between the inter-element shield layer39and the waveguide35, though not shown in the figure. The backing coil portion is a coil portion for generating magnetic flux to negate a magnetic flux loop that is generated from the electromagnetic transducer34and passes through the upper and lower shield layers334and330of the MR element33. Thus, the backing coil portion intends to suppress wide adjacent track erasure (WATE), that is, unwanted writing or erasing to the magnetic disk. Here, the insulating layers381,382,383,384and385constitute the overcoat layer38.

FIG. 4shows a plan view schematically illustrating the configuration of the waveguide35, the surface plasmon antenna36, the head element32and the laser diode40that are arranged in the element-integration surface2102. In the figure, the head element32is depicted in broken lines for easy viewing of the figure.

As shown inFIG. 4, the waveguide35extends in a curve from the light-receiving end surface352, which receives the laser light emitted from the light-emission center4000of the laser diode40, to the end surface350on the head end surface388side. As a result, the laser light (waveguide light) incident on the light-receiving end surface352and propagating through the waveguide35travels forward in a curve, and reaches a portion facing the surface plasmon antenna36. On this occasion, while total reflection occurs on the side surfaces, including the curved surface portions, of the waveguide35, the waveguide light propagates inside the waveguide35with the traveling direction curved. In the present embodiment, the portion of the waveguide35near the head end surface388and the surface plasmon antenna36extend in the direction perpendicular to the edge2102aof the element-integration surface2102(to head end surface388) (That is, θPW=0° inFIG. 8d). While, the light-receiving end surface352of the waveguide35is preferably inclined at a predetermined acute angle θ352from the end surface400including the light-emission center4000of the laser diode40. The angle θ352is, for example, approximately 4°. This inclination prevents the light-returning phenomenon in which the laser light reflected off the light-receiving end surface352returns to the light-emission center4000. Thus, since the waveguide35extends in a curve in the element-integration surface2102, even when the laser diode40is placed in the element-integration surface2102and further the optical axis4000ais directed toward the track width direction (Y-axis direction), the waveguide light can be propagated up to the vicinity of the head end surface388and coupled with the surface plasmon antenna36.

A width WWG1in the vicinity of the light-receiving end surface352of the waveguide35may be, for example, approximately 0.5 to 200 μm. The width of the waveguide35becomes gradually thinner along the travelling direction of the waveguide light. That is, opposed side surfaces351become gradually closer to each other along the travelling direction of the waveguide light. As a result, a width WWG2in the vicinity of the end surface350in the track width direction (Y-axis direction) can be made to a smaller value than the width WWG1, for example, approximately 0.3 to 100 μm. As described above, in the thermally-assisted magnetic recording head21according to the present invention, while the laser diode40, which has a sufficiently large output power for thermally assisting, is disposed in the element-integration surface2102of the slider substrate210to achieve improvement of mass-productivity, a diffraction optical element such as a diffraction grating or the like is not necessitated to be used for directing the laser light toward the head end surface388. As a result, even when the wavelength fluctuation of the laser light due to the change of surrounding temperature occurs, the laser light can be securely transmitted to the desired position in the vicinity of the head end surface388.

The laser diode40can be provided in a concave portion389formed on the element-integration surface2102, where the overcoat layer38does not exist. The setting method including formation of the concave portion389will be explained in detail later. The laser diode40is positioned apart from wall surfaces386and387surrounding the concave portion389of the overcoat layer by predetermined distances DL1and DL2, respectively, so as to be aligned relative to the waveguide35and to avoid receiving unnecessary stress in the setting procedure. The distances DL1and DL2may be set to be, for example, 2±1 μm and 6±1 μm, respectively.

FIG. 5shows a perspective view schematically illustrating the configuration of the waveguide35, the surface plasmon antenna36and the main magnetic pole layer340. In the figure, the head end surface388is positioned at the left side, the surface388including positions where write field and near-field light are emitted toward the magnetic recording medium.

As shown inFIG. 5, the configuration includes the waveguide35for propagating laser light53used for generating near-field light, and the surface plasmon antenna36that has a propagation edge360as an edge on which surface plasmon excited by the laser light53propagates. Further, the buffering portion50is a portion sandwiched between a portion of the side surface354of the waveguide35and a portion of the lower surface362including the propagation edge360of the surface plasmon antenna36, the portions being opposed to each other. That is, a portion of the propagation edge360is covered with the buffering portion50. The buffering portion50acts for coupling the laser light53with the surface plasmon antenna36in a surface plasmon mode. Here, side surfaces of the waveguide35are defined as, out of end surfaces surrounding the waveguide35, end surfaces other than the end surface350on the head end surface388side and the rear end surface352on the opposite side, the end surfaces350and352being perpendicular to the propagating direction (−X direction) of the laser light53. The curved surfaces351are also side surfaces. These side surfaces serve as surfaces on which the propagating laser light53can be totally reflected in the waveguide35that corresponds to a core. In the present embodiment, the side surface354of the waveguide35, a portion of which is in surface contact with the buffering portion50, is the upper surface of the waveguide35. And, the buffering portion50may be a portion of the overcoat layer38(FIG. 2), or may be provided as a new layer other than the overcoat layer38.

Further, the surface plasmon antenna36has a near-field light generating end surface36areaching the head end surface388. The near-field light generating end surface36ais close to an end surface3400eof the main magnetic pole3400, the surface3400ereaching the head end surface388. Moreover, the propagation edge360extends from its portion covered with the buffering portion50to the near-field light generating end surface36a, the covered portion being coupled with the laser light53in a surface plasmon mode. Thus, the propagation edge360acts for propagating the surface plasmon excited by the laser light53to the near-field light generating end surface36a. A portion on the head end surface388side of the propagation edge360has a straight or curved line shape extending so as to become closer to the end surface361on the side opposite to the edge360of the surface plasmon antenna36toward the near-field light generating end surface36a. The propagation edge360can be made rounded to prevent surface plasmon from running off from the edge360. The curvature radius of the rounded edge may be, for example, in the range of 5 to 500 nm.

Further, in the present embodiment, the surface plasmon antenna36tapers toward the near-field light generating end surface36ain the height direction (Z-axis direction) near the head end surface388. And the surface plasmon antenna36has a cross-section taken by YZ plane with a triangular shape, especially, has a predetermined triangular shape in the vicinity of the head end surface388. Accordingly, in the present embodiment, the near-field light generating end surface36ahas a triangular shape (FIG. 6) in which one apex is the end of the propagation edge360reaching the end surface36a. Thus, surface plasmon propagating on the propagation edge360reaches the near-field light generating end surface36a, and then causes near-field light to be generated from the end surface36a.

The waveguide35and the buffering portion50are provided in −Z direction side, that is, in the side opposite to the main magnetic pole3400in relation to the surface plasmon antenna36. As a result, the propagation edge360, which is covered with the buffering portion50, is also positioned on the side opposite to the main magnetic pole3400in the surface plasmon antenna36. By applying such a configuration, even when a distance between the end surface3400egenerating write field of the main magnetic pole3400and the end surface36aemitting near-field light is sufficiently small, preferably 100 nm or less, the waveguide35can be sufficiently separated apart from the main magnetic pole3400and the main pole body3401. As a result, there can be avoided such a situation in which a part of the laser light53is absorbed into the main magnetic pole3400and main pole body3401made of metal and the amount of light to be converted into the near-field light is reduced. Further, the waveguide35can have a cross-section with a rectangular, square or trapezoidal shape at the portion opposed to the surface plasmon antenna36through the buffering portion50. The width WWG2in the track width direction (Y-axis direction) of a portion on the end surface350side of the waveguide35may be, for example, in the range approximately from 0.3 to 100 μm. And the thickness TWG(in Z-axis direction) may be, for example, in the range approximately from 0.1 to 4 μm.

Further, the side surfaces of the waveguide35: the upper surface354, the lower surface353, and both the side surfaces351in the track width direction (Y-axis direction) have a contact with the overcoat layer38(FIG. 2) except the portion having a surface contact with the buffering portion50. Here, the waveguide35is formed of a material with refractive index nWGhigher than refractive index nOCof the constituent material of the overcoat layer38, made by using, for example, a sputtering method. For example, in the case that the wavelength λLof the laser light is 600 nm and the overcoat layer38is formed of SiO2(n=1.5), the waveguide35can be formed of, for example, Al2O3(n=1.63). Further, in the case that the overcoat layer38is formed of Al2O3(n=1.63), the waveguide35can be formed of, for example, SiOXNY(n=1.7-1.85), Ta2O5(n=2.16), Nb2O5(n=2.33), TiO (n=2.3-2.55) or TiO2(n=2.3-2.55). This material structure of the waveguide35enables the propagation loss of laser light53to be reduced due to the excellent optical characteristics of the constituent material. Further, the waveguide35acting as a core can provide the total reflection in all its side surfaces due to the existence of the overcoat layer38acting as a clad. As a result, more amount of laser light53can reach the position of the buffering portion50, which improves the propagation efficiency of the waveguide35.

Furthermore, alternatively, the waveguide35may have a multilayered structure of dielectric materials in which the upper a layer is, the higher becomes the refractive index n of the layer. The multilayered structure can be realized, for example, by sequentially stacking dielectric materials of SiOXNYwith the composition ratios X and Y appropriately changed. The number of stacked layers may be, for example, in the range from 8 to 12. In the case that laser light53has a linear polarization in Z-axis direction, the above-described structure enables the laser light53to propagate along the course closer to the buffering portion50. In this case, by choosing the composition and layer thickness in each layer, and the number of layers of the multilayered structure, the laser light53can propagate through the desired positions in Z-axis direction.

The surface plasmon antenna36is preferably formed of a conductive material of, for example, metal such as Pd, Pt, Rh, Ir, Ru, Au, Ag, Cu or Al, or an alloy made of at least two of these elements. Further, the surface plasmon antenna36can have a width WNFin the track width direction (Y-axis direction) sufficiently smaller than the wavelength of the laser light53, for example, of approximately 10 to 100 nm. And the surface plasmon antenna36can have a thickness TNF1(in Z-axis direction) sufficiently smaller than the wavelength of the laser light53, thickness TNF1being, for example, in the range of approximately 10 to 100 nm. Further, the thickness TNF(in Z-axis direction) can be set to be sufficiently smaller than the wavelength of the laser light53and, for example, in the range of approximately 10 to 100 μm; and the length (height) HNF(in X-axis direction) can be set to be, for example, in the range of approximately 0.8 to 6.0 μm.

The buffering portion50is formed of a dielectric material having refractive index nBFlower than the refractive index nWGof the waveguide35. For example, when the wavelength λLof the laser light is 600 nm and the waveguide35is formed of Al2O3(n=1.63), the buffering portion50may be formed of SiO2(n=1.46). Further, when the waveguide35is formed of Ta2O5(n=2.16), the buffering portion50may be formed of SiO2(n=1.46) or Al2O3(n=1.63). In these cases, the buffering portion50can be a portion of the overcoat layer38(FIG. 2) serving as a clad made of SiO2(n=1.46) or Al2O3(n=1.63).

The length (in X-axis direction) of the buffering portion50, namely, the length LBFof a coupling portion between the waveguide35and the surface plasmon antenna36is preferably in the range of 0.5 to 5 μm, and is more preferably larger than the wavelength λLof the laser light53. In this preferable case, the coupling portion has an area markedly larger than a so-called “focal region” in the case that, for example, laser light is converged on a buffering portion50and a surface plasmon antenna36and coupled in a surface plasmon mode. As a result, the coupling portion enables very stable coupling in the surface plasmon mode. Preferably, the thickness TBF(in Z-axis direction) of the buffering portion50is in the range of 10 to 200 nm. These length LBFand thickness TBFare important parameters for obtaining proper excitation and propagation of surface plasmon.

The end on the head end surface388side of the buffering portion50is positioned apart from the head end surface388by a distance DBFin X-axis direction. The propagation distance of surface plasmon is adjusted by the distance DBF. Alternatively, the buffering portion50and the waveguide35may extend along the propagation edge360and reach the head end surface388. In this alternative, the coupling portion between the waveguide35and the surface plasmon antenna36extends over the entire length of the propagation edge360. Further, as another alternative, it is preferable that a groove is formed in the upper surface (side surface)354of the waveguide35, and a portion of the propagation edge360opposed to the waveguide35is embedded in the groove or is located directly above the groove. This preferable configuration enables more amount of waveguide light to be coupled with the surface plasmon antenna36.

Also as shown inFIG. 5, a thermal conduction layer51is preferably provided on the head end surface388side between the surface plasmon antenna36and the first main pole portion3400a. The thermal conduction layer51is formed of, for example, an insulating material such as AlN, SiC or DLC, which has higher thermal conductivity compared with that of the overcoat layer38(FIG. 2). The arrangement of such a thermal conduction layer51allows a part of the heat generated when the surface plasmon antenna36emits near-field light to get away to the main magnetic pole3400and the main pole body3401through the thermal conduction layer51. That is, the main magnetic pole3400and the main pole body3401can be used as a heatsink. As a result, excessive temperature rise of the surface plasmon antenna36can be suppressed, and there can be avoided unwanted protrusion of the near-field light generating end surface36aand substantial reduction in the light use efficiency of the surface plasmon antenna36.

The thickness TTCof the thermal conduction layer51corresponds to a distance DN-P(FIG. 6) on the head end surface388between the near-field light generating end surface36aand the end surface3400eof the main magnetic pole3400, and is set to be a sufficiently small value of 100 nm or less. Further, the refractive index nIN2of the thermal conduction layer51is set equal to or lower than the refractive index nIN1of the insulating layer52that covers the propagation edge360of the surface plasmon antenna36. That is, the propagation edge360of the surface plasmon antenna36is covered with a material having a refractive index nIN1equal to or higher than the refractive index nIN2of a material covering the end surface361opposite to the edge360. This allows surface plasmon to propagate stably on the propagation edge360. It is known to be preferable in practice to satisfy the relation of (refractive index nIN1)≧(refractive index nIN2)×1.5.

Also according toFIG. 5, the main magnetic pole layer340includes, as described-above, the main magnetic pole3400and the main pole body3401. The main magnetic pole3400includes; the first main pole portion3400ahaving the end surface3400ereaching the head end surface388; and the second main pole portion3400b, the end portion on the head end surface388side of which is overlapped on a portion of the first main pole portion3400a, the portion being on the side opposite to the head end surface388. Further, the end portion on the head end surface388side of the main pole body3401is overlapped on a portion of the second main pole portion3400b, the portion being on the side opposite to the head end surface388. Namely, the end portion on the head end surface388side of the main magnetic pole layer340extends slantwise relative to the element-integration surface2102(FIG. 3), and become closer to the end portion on the head end surface388side of the surface plasmon antenna36toward the surface388. As a result, the end surface3400eof the main magnetic pole layer340can be made sufficiently close to the near-field light generating end surface36a, under the condition that the main magnetic pole layer340is sufficiently separated apart from the waveguide35.

FIG. 6shows a plan view illustrating the shapes of the end surfaces of the surface plasmon antenna36and the electromagnetic transducer34on the head end surface388.

As shown inFIG. 6, the main magnetic pole3400(the first main pole portion3400a) and the write shield layer345(the trailing shield3450) of the electromagnetic transducer34reach the head end surface388. The shape of the end surface3400eof the main magnetic pole3400on the head end surface388is, for example, a rectangle, a square or a trapezoid. Here, the above-described width WPis a length of the edge along the track width direction (Y-axis direction) of the end surface3400eof the main magnetic pole3400, and provides the width of a track formed on the magnetic recording layer of the magnetic disk. The width WPis, for example, in the range of approximately 0.05 to 0.5 μm.

Moreover, on the head end surface388, the near-field light generating end surface36aof the surface plasmon antenna36is positioned close to the end surface3400eof the main magnetic pole3400and in the leading side (−Z side) of the end surface3400e. Here, a distance DN-Pbetween the near-field light generating end surface36aand the end surface3400eis set to be a sufficiently small value of, for example, 100 nm or less, preferably 20 nm or more, and more preferably 30 nm or more. In the thermally-assisted magnetic recording according to the present invention, the near-field light generating end surface36afunctions as a main heating action part, and the end surface3400efunctions as a writing action part. Therefore, write field with sufficiently large gradient can be applied to a portion of the magnetic recording layer of the magnetic disk, which has been sufficiently heated. This enables a stable thermally-assisted write operation to be securely achieved.

Furthermore, in the present embodiment, the near-field light generating end surface36ahas a shape of isosceles triangle on the head end surface388, which has a bottom edge361aon the trailing side (+Z side) and an apex on the leading side (−Z side) that is an end360aof the propagation edge360. The height TNF2of the near-field light generating end surface36a(the thickness of the surface plasmon antenna36on the head end surface388) is preferably 100 nm or less, and more preferably 30 nm or less. Thereby, the near-field-light emitting position on the end surface36abecomes close to the edge361aon the trailing side, that is, closer to the end surface3400eof the main magnetic pole3400. Further, the apex angle θNFof the apex360aof the isosceles triangle is preferably 60 to 130 degrees, and more preferably 80 to 110 degrees. This adjustment of the apex angle θNFenables the near-field-light emitting position on the end surface36ato be further on the trailing side. Here, the above-described values of TNF2and θNFare true in the case that the surface plasmon antenna36extends in the direction perpendicular to the head end surface388(edge2102a).

Further, a distance DW-Pbetween the waveguide35and the main magnetic pole3400is made sufficiently large while the distance DN-Pis set to a minute value as described above. That is, by applying the configuration according to the present invention shown inFIG. 5, the waveguide35can be sufficiently separated apart from the main magnetic pole3400and the main pole body3401. As a result, there can be avoided such a situation in which a part of the laser light is absorbed into the main magnetic pole3400and the main pole body3401made of metal, and the amount of light to be converted into near-field light is reduced.

FIG. 7shows a schematic diagram for explaining the thermally-assisted magnetic recording utilizing the surface plasmon mode according to the present invention.

Referring toFIG. 7, when the electromagnetic transducer34writes data onto the magnetic recording layer of the magnetic disk10, first, laser light emitted from the laser diode40propagates through the waveguide35. Next, the waveguide light53, which has advanced to near the buffering portion50, couples with the optical configuration including the waveguide35with a refractive index nWG, the buffering portion50with a refractive index nBFand the surface plasmon antenna36made of a conductive material such as metal, and induces a surface plasmon mode on the propagation edge360of the surface plasmon antenna36. That is, the waveguide light couples with the surface plasmon antenna36in the surface plasmon mode. Actually, evanescent light is excited within the buffering portion50under an optical boundary condition between the waveguide35as a core and the buffering portion50. Then, the evanescent light couples with the fluctuation of electric charge excited on the metal surface (propagation edge360) of the surface plasmon antenna36, and induces the surface plasmon mode. To be exact, there excited is surface plasmon polariton in this system because surface plasmon as elementary excitation is coupled with an electromagnetic wave. However, the surface plasmon polariton will be hereinafter referred to as surface plasmon for short.

The propagation edge360is located closest to the waveguide35on the inclined lower surface362of the surface plasmon antenna36, and is just an edge where electric field tends to converge; thus surface plasmon can easily be excited on the edge360. In this case, the surface plasmon mode can be induced by setting the refractive index nBFof the buffering portion50lower than the refractive index nWGof the waveguide35(nBF<nWG), and further by properly selecting the length (in X-axis direction) of the buffering portion50, namely, the length LBFof the coupling portion between the waveguide35and the surface plasmon antenna36, and the thickness TBF(in Z-axis direction) of the buffering portion50. In the induced surface plasmon mode, the surface plasmon60is excited on the propagation edge360of the surface plasmon antenna36, and propagates on the propagation edge360along the direction shown by arrows61. The propagation of the surface plasmon60can occur under the condition that the propagation edge360of the surface plasmon antenna36is covered with a material having refractive index nIN1equal to or higher than the refractive index nIN2of a material covering the end surface361on the side opposite to the edge360. It is known to be preferable in practice to satisfy the relation of (refractive index nIN1)=(refractive index nIN2)×1.5. InFIG. 7, the refractive index nIN2of the thermal conduction layer51is set so as to be lower than the refractive index nIN1of the insulating layer52covering the propagation edge360of the surface plasmon antenna36.

By the above-described propagation of the surface plasmon60, the surface plasmon60, namely, electric field converges in the near-field light generating end surface36athat reaches the head end surface388and includes the apex36athat is the destination of the propagation edge360. As a result, near-field light62is emitted from the near-field light generating end surface36a. The near-field light62is radiated toward the magnetic recording layer of the magnetic disk10, and reaches the surface of the magnetic disk10to heat a portion of the magnetic recording layer of the magnetic disk10. This heating reduces the anisotropic magnetic field (coercive force) of the portion to a value with which write operation can be performed. Immediately after the heating, write field63generated from the main magnetic pole3400is applied to the portion to perform write operation. Thus, the thermally-assisted magnetic recording can be achieved.

As described above, by adjusting the shape and size of the near-field light generating end surface36aon the head end surface388, the emitting position of near-field light62on the end surface36acan be set to be closer to the first main pole portion3400aon the trailing side (on the edge361aside). As a result, write field with sufficiently large gradient can be applied to a portion of the magnetic recording layer of the magnetic disk10, which has been sufficiently heated. This enables a stable thermally-assisted write operation to be securely achieved.

Further, the propagation edge360, for propagating surface plasmon60, of the surface plasmon antenna36according to the present invention is a propagation region with a very narrow width in the track width direction. In the present embodiment, the cross-section taken by YZ plane of the surface plasmon antenna36has a triangular shape, especially a predetermined triangular shape in the vicinity of the head end surface388. Therefore, the near-field light generating end surface36a, which appears as a polished surface on the head end surface388formed through polishing process in the head manufacturing, can be made a desired shape (a triangle in the present embodiment) with a very small size, and further can be set in such a way that surface plasmon propagates to reach the end surface36areliably.

Furthermore, in a conventional case in which a plasmon antenna provided on the end surface of a head is directly irradiated with the waveguide light, most of the irradiated laser light has been converted into thermal energy within the plasmon antenna. In this case, the size of the plasmon antenna has been set equal to or smaller than the wavelength of the laser light, and its volume is very small. Therefore, the plasmon antenna has been brought to a very high temperature, for example, 500° C. (degrees Celsius) due to the thermal energy. On the contrary, in the thermally-assisted magnetic recording according to the present invention, the surface plasmon mode is used, and the near-field light62is generated by propagating the surface plasmon60toward the head end surface388. This brings the temperature at the near-field light generating end surface36ato, for example, about 100° C. during the emission of near-field light, which is greatly reduced compared to the conventional. This reduction of temperature allows the protrusion of the near-field light generating end surface36atoward the magnetic disk10to be suppressed; thereby favorable thermally-assisted magnetic recording can be achieved.

Furthermore, the length LBFof the whole buffering portion50, that is, the portion through which the waveguide35and the surface plasmon antenna36are coupled with each other in a surface plasmon mode, is preferably larger than the wavelength λLof the laser light. In this preferable case, the coupling portion has an area markedly larger than a so-called “focal region” in the case that, for example, laser light is converged on a buffering portion and a surface plasmon antenna and coupled in a surface plasmon mode. Therefore, the configuration quite different from the system including such “focal region” can be realized in the present invention; thus, very stable coupling in the surface plasmon mode can be achieved. The induction of surface plasmon mode is disclosed in, for example, Michael Hochberg, Tom Baehr-Jones, Chris Walker & Axel Scherer, “Integrated Plasmon and dielectric waveguides”, OPTICS EXPRESS Vol. 12, No. 22, pp 5481-5486 (2004), US patent Publication No. 2005/0249451 A1, and U.S. Pat. No. 7,330,404 B2.

FIGS. 8a1to8gshow schematic diagrams illustrating various embodiments of the thermally-assisted magnetic recording head according to the present invention.

In embodiments shown inFIGS. 8a1and8a2, the arrangement of the waveguide35, the surface plasmon antenna36, the main magnetic pole layer340and the laser diode40is the same as that shown inFIGS. 3,4and5. However, a write shield layer70, which is a return yoke for receiving the magnetic flux returned from a magnetic disk, is provided in the side opposite to the main magnetic pole layer340in relation to the waveguide35and the surface plasmon antenna36, that is, in the leading side (−Z side) of the waveguide35and the surface plasmon antenna36. And the write shield layer70is magnetically connected to the main magnetic pole layer340with a back contact portion71. Further, a write coil layer343′ is formed so as to pass through at least between the main magnetic pole layer340and the write shield layer70during one turn, and has a spiral structure in which the coil layer is wound around the back contact portion71as the center.

Accordingly, the portion on the head end surface388side of the waveguide35and the surface plasmon antenna36are positioned between the write shield layer70and the main magnetic pole layer340as shown inFIG. 8a1. In spite of this arrangement, since the waveguide35extends in a curve from the laser diode40as shown inFIG. 8a2, the waveguide35can reach the vicinity of the surface plasmon antenna36, keeping away from the back contact portion71. With this curved structure, it becomes unnecessary to employ a special structure for the waveguide35to pass through the back contact portion71. This makes it possible to avoid the increase of man-hour and the reduction of process yield. This curved structure also makes it possible to avoid absorption of the waveguide light by the back contact portion71, thereby to lower and suppress the propagation loss in the waveguide35. As a result, desirable thermally-assisted magnetic recording using a surface plasmon antenna can be performed.

According to the embodiment shown inFIG. 8b, similarly to the embodiment ofFIG. 2, the laser diode40is disposed in the element-integration surface2102in such a way that the edge401in the direction along the optical axis4000ais parallel with the edge2102aof the element-integration surface2102. There is provided a waveguide73having a portion extending in Y-axis direction and a portion extending in X-axis direction, and further, a mirror72acting as a light-path changing means is provided between these portions of the waveguide73. The mirror72changes the traveling direction of the waveguide light, which has propagated from the light-emission center4000of the laser diode40through the portion extending in Y-axis direction of the waveguide73, to a direction toward the head end surface388; then the waveguide light is directed toward the surface plasmon antenna36through the portion extending in X-axis direction of the waveguide73. The mirror72can be a triangle pole extending in Z-axis direction and having a surface for reflecting laser light, which is formed of a metal such as Au, Cu, NiFe or the like. By using the optical system described above, even when the laser diode40is disposed in the element-integration surface2102and the optical axis4000ais directed toward the track width direction (Y-axis direction), the waveguide light can be propagated up to the vicinity of the head end surface388and coupled to the surface plasmon antenna36.

According to the embodiment shown inFIG. 8c, the laser diode40is disposed in such a way that the edge401in the direction along the optical axis4000ais inclined within the element-integration surface2102at a predetermined acute angle θLDfrom the edge2102aof the element-integration surface2102. This inclined configuration allows the overall curvature of a waveguide74to be made smaller by the acute angle θLD, the waveguide74optically connecting between the light-emission center4000of the laser diode40and the surface plasmon antenna36. As a result, a ratio of the waveguide light leaking from the waveguide74is reduced, and the propagation loss can be more suppressed. Here, considering a case that the laser diode40is set without protruding from the element-integration surface2102afor maintaining cooling efficiency of the laser diode40during operation, the maximum acute angle MAXθLDto be set for the acute angle θLDis given by:
MAXθLD=sin−1(TSL*(LLD2+WLD2)−0.5)−tan−1(WLD/LLD).  (1)

According to the embodiment shown inFIG. 8d, similarly to the embodiment ofFIG. 2, the laser diode40is disposed in the element-integration surface2102in such a way that the edge401in the direction along the optical axis4000ais parallel with the edge2102aof the element-integration surface2102. The waveguide75extends to the vicinity of the surface plasmon antenna76so that the laser light emitted from the light-emission center4000of the laser diode40can be coupled with the surface plasmon antenna76. Here, a longitudinal axis76aof the surface plasmon antenna76and side surfaces751of a portion of the waveguide75near the head end surface388are inclined within the element-integration surface2102at an inclination angle θPWfrom a direction perpendicular to the edge2102a(to the head end surface388) toward the end surface400including the light-emission center4000. By arranging the surface plasmon antenna76and the portion near the head end surface388of the waveguide75with an inclination as in the present embodiment, the overall curvature of the waveguide75can be made smaller by the inclination angle θPW. As a result, a ratio of the waveguide light leaking from the waveguide75is reduced, and the propagation loss can be more suppressed. Here, the surface plasmon antenna76is also inclined along the waveguide light propagating through the portion near the head end surface388of the waveguide75; therefore, the degree of coupling between the waveguide light and the surface plasmon antenna76is not reduced even by setting the inclination angle θPW.

The inclination angle θPWis preferably 00 (degree) or more, and 30° or less, as will be explained with use of practical examples later. By setting the inclination angle θPWto 30° or less, a spot diameter of the light (near-field light) in the near-field light generating end surface of the surface plasmon antenna76can become sufficiently small. Thereby, the near-field light can effectively heat a desired portion on the magnetic recording layer of a magnetic disk.

According to the embodiment ofFIG. 8e, similarly toFIG. 8c, the laser diode40is disposed in such a way that the edge401in the direction along the optical axis4000ais inclined within the element-integration surface2102at a predetermined acute angle θLDfrom the edge2102aof the element-integration surface2102. While the surface plasmon antenna76is, similarly toFIG. 8d, provided in such a way that its longitudinal axis76ais inclined within the element-integration surface2102at an inclination angle θPWfrom a direction perpendicular to the edge2102atoward the end surface400including the light-emission center4000. Here, by setting the sum of the acute angle θLDand the inclination angle θPWto be approximately 90°, the overall curvature of the waveguide77becomes zero, the waveguide77optically connecting between the light-emission center4000of the laser diode40and the surface plasmon antenna76, thus the waveguide77can be a linear path. As a result, a phenomenon of leakage of the waveguide light due to the curvature of the waveguide path can be prevented, and the propagation loss can be more suppressed.

According toFIG. 8f, a light-emission center4000′ and an optical axis4000a′ of a laser diode40′ are shifted to the edge401′ side from a centerline indicating a center of the laser diode40′ in the width WLDdirection (X-axis direction). In the present embodiment, the laser diode40′ is disposed in such a way that the edge401′ is parallel with the edge2102aof the element-integration surface2102. Further, a mirror78and a waveguide79are provided in a similar arrangement to that ofFIG. 8b. The mirror78changes the traveling direction of the waveguide light, which has propagated from the light-emission center4000′ of the laser diode40′ through the portion extending in Y-axis direction of the waveguide79, to a direction toward the head end surface388; thus, the waveguide light is directed toward the surface plasmon antenna36through the portion extending in X-axis direction of the waveguide79. In this case, the light-emission center4000′ and the optical axis4000a′ are positioned closer to the head end surface388compared to the light-emission center4000and the optical axis4000ashown inFIG. 8b. Accordingly, the length of the portion extending in X-axis direction of the waveguide79can be set smaller than that of the portion extending in X-axis direction of the waveguide73shown inFIG. 8b. As a result, the waveguide length of the whole waveguide79can be made shorter, and the propagation loss in the whole waveguide79can be more reduced.

According toFIG. 8g, a light-emission center4000″ and an optical axis4000a″ of a laser diode40″ are shifted to the side opposite to an edge401″ from a centerline indicating a center of the laser diode40″ in the width WLDdirection (X-axis direction). In the present embodiment, the laser diode40″ is disposed in such a way that the edge401″ is parallel with the edge2102aof the element-integration surface2102. Moreover, a waveguide80, similarly to the waveguide35shown inFIG. 4, extends in a curve from the light-emission center4000″ to the vicinity of the surface plasmon antenna36. In this case, the light-emission center4000″ and the optical axis4000a″ are positioned farther from the head end surface388compared to the light-emission center4000and the optical axis4000ashown inFIG. 4. Accordingly, the curvature of the whole waveguide80can be made smaller. As a result, a ratio of the waveguide light leaking from the waveguide80due to the curvature can be more reduced.

The shifting of the light-emission center and the optical axis from a centerline indicating the center in the width direction as in the laser diodes40′ and40″ shown inFIGS. 8fand8gcan be implemented, for example, by shifting the positions of two grooves in a ridge structure formed on the p-electrode side of a laser diode. In this case, the light-emission center is positioned between the two grooves.

FIG. 9shows a cross-sectional view illustrating another embodiment in the HGA according to the present invention.

According to the embodiment ofFIG. 9, a thermally-assisted magnetic recording head21′ is provided with a laser diode81, the waveguide35and the surface plasmon antenna36on the element-integration surface2102′. The laser diode81includes a second light-emission center8100′ on the side opposite to the light-emission center8100from which laser light is emitted toward the waveguide35. By detecting the laser light emitted from the second light-emission center8100′ by a photo-detector, feedback adjustment for output of the laser diode81can be performed. With this adjustment, there can be suppressed the output change of the laser diode81depending on its environment and the output change over time of the laser diode81; thus the intensity of near-field light emitted from the surface plasmon antenna36can be stabilized. As a result, proper heating of the magnetic recording layer of a magnetic disk can be secured.

Referring also toFIG. 9, a mirror83as a light-path changing means and a detection-waveguide84used for light detection are provided, in the element-integration surface2102′, on the side opposite to the head element32in relation to the laser diode81. Further, there is provided a through-hole2010′ in a flexure201′ that supports the thermally-assisted magnetic recording head21′, and a photodiode82, as a photo-detector for sensing the laser light emitted from the laser diode81, is fixed on the surface of the flexure201′ on the opposite side to the head21′. A light-receiving window820of the photodiode82is positioned so as to receive the laser light from the detection-waveguide84through the through-hole2010′. The alignment accuracy of the positioning is not required to be so high as in the optical system including the waveguide35and the surface plasmon antenna36. Therefore, the laser-light output can be securely measured and monitored even when the HGA is in use. Terminal electrodes821of the photodiode82may be electrically connected to the connection pads of the wiring member provided on the flexure201′.

The detection-waveguide84for light detection has a portion extending in Y-axis direction and a portion extending in X-axis direction. While, the mirror83for light detection is arranged between these portions of the waveguide84. The mirror83changes the traveling direction of the waveguide light, which has propagated from the second light-emission center8100′ of the laser diode81through the portion extending in Y-axis direction of the waveguide84, to a direction toward the head end surface387on the side opposite to the head end surface388. The waveguide light is launched into the light-receiving window820of the photodiode82, through the portion extending in X-axis direction of the waveguide84and the through-hole2010′ of the flexure201′. This configuration enables the output of the laser diode81to be always measured and monitored, thereby performing the feedback adjustment. In the present embodiment, it is not necessary that the photodiode82for feedback adjustment is provided within the thermally-assisted magnetic recording head21′. As a result, manufacturing of the head21′ becomes relatively easier, and the manufacturing yield is improved.

Configuration of performing feedback adjustment for the output of the laser diode81is not limited to the present embodiment. For example, a photodiode may be placed in the vicinity of the side surface351of the waveguide35in the embodiment shown inFIG. 4to measure and monitor the light leaking from the waveguide35.

FIG. 10shows a block diagram illustrating the circuit structure of the recording/reproducing and light-emission control circuit13of the magnetic disk apparatus shown inFIG. 1. In the embodiment shown in this figure, the target to be controlled is the HGA shown inFIG. 9, in which the feedback adjustment can be performed for the output of the laser diode81.

According toFIG. 10, reference numeral90indicates a control LSI,91indicates a write gate for receiving recording data from the control LSI90,92indicates a write circuit,93indicates a ROM that stores a control table or the like for controlling the value of drive current supplied to the laser diode,95indicates a constant current circuit for supplying sense current to the MR element33,96indicates an amplifier for amplifying the output voltage from the MR element33,97indicates a demodulator circuit for outputting reproduced data to the control LSI90,98indicates a temperature detector, and99indicates a control circuit for controlling the laser diode81, respectively.

The recording data outputted from the control LSI90is supplied to the write gate91. The write gate91supplies recording data to the write circuit92only when a recording control signal outputted from the control LSI90instructs a write operation. The write circuit92applies write current according to this recording data to the write coil layer343, and then a write operation is performed onto the magnetic disk with write field generated from the main magnetic pole3400.

A constant current flows from the constant current circuit95into the MR multilayer332only when the reproducing control signal outputted from the control LSI90instructs a read operation. The signal reproduced by the MR element33is amplified by the amplifier96, demodulated by the demodulator circuit97, and then, the obtained reproduced data is outputted to the control LSI90.

The laser control circuit99receives a laser ON/OFF signal and a laser power control signal, which are outputted from the control LSI90. When the laser ON/OFF signal indicates an ON operation instruction, a drive current of an oscillation threshold value or more is applied into the laser diode81. Thereby, the laser diode81emits light; then the laser light propagates through the waveguide35and couples with the surface plasmon antenna36in a surface plasmon mode. As a result, near-field light is generated from the end of the surface plasmon antenna36, and then the magnetic recording layer of the magnetic disk is irradiated with the near-field light, which heats the magnetic recording layer. The value of the drive current in this occasion is controlled to such a value that the laser diode81emits a laser light whose output is specified by the laser power control signal. The control LSI90generates the laser ON/OFF signal with its timing adjusted according to recording/reproducing operations, and determines the value of the laser power control signal by referring the value of temperature in the magnetic recording layer of the magnetic disk or the like, which is measured by the temperature detector98, based on the control table in the ROM93. Here, the control table may include data about the relation between the drive current value and the mount of temperature increase by thermal-assist operation in the magnetic recording layer, and data about the temperature independence of the anisotropic magnetic field (coercive force) of the magnetic recording layer, as well as the temperature dependences of the oscillation threshold value and the characteristics of light output vs. drive current. Thus, it is possible to realize not only a current application to the laser diode81linked simply with the recording operation but also more diversified current application modes, by providing the system of the laser ON/OFF signal and the laser power control signal independently from the recording/reproducing control signal system.

The photodiode82fixed on the flexure201′ measures and monitors the output of the laser diode81, and sends the measured values to the laser control circuit99. The laser control circuit99performs the feedback adjustment with use of the measured values, and adjusts the drive current applied to the laser diode81in such a way that the laser diode81emits a laser light whose output is specified by the laser power control signal.

Obviously, the circuit structure of the recording/reproducing and light-emission control circuit13is not limited to that shown inFIG. 10. It is also possible to specify write and read operations by using a signal other than the recording control signal and reproducing control signal.

FIGS. 11a1to11cshow schematic diagrams explaining one embodiment of a method for mounting the laser diode40in the element-integration surface2102of the slider substrate210, in the method for manufacturing the thermally-assisted magnetic recording head according to the present invention. Here,FIGS. 11a2and11b2are cross-sectional views taken along lines B-B and C—C ofFIGS. 11a1and11b1, respectively.

As shown inFIGS. 11a1and11a2, first, formed on the element-integration surface2102of the slider substrate210is a base layer380, made of an insulating material such as Al2O3(alumina), SiO2or the like. Next, formed on the base layer380is a lead electrode4100made of a conductive material such as Au or the like. Further, there is formed a mask85for forming a concave portion389that includes a position where the laser diode40is to be placed later, so as to cover the formed lead electrode4100. The mask85can be formed of a metal such as, for example, NiFe (Permalloy), which can be etched selectively so as to leave the material such as Au forming the lead electrode4100. Here, each of the base layer380, the lead electrode4100and the mask85can be formed by using, for example, a sputtering method.

Next, as shown inFIGS. 11b1and11b2, the MR element33, the waveguide35, the surface plasmon antenna36and the electromagnetic transducer34are sequentially formed in a predetermined position of the base layer380. In these formations, these elements are set in such a way that a distance DW-Sbetween a centerline indicating the center of the waveguide35in the stacking direction (Z-axis direction) and the upper surface of the base layer380is equal to a distance between the light-emission center4000of the laser diode40, which is to be disposed later, and the upper surface of the base layer380. Then, an overcoat layer38is formed within the element-integration surface2102so as to cover these elements. Thereafter, terminal electrodes including terminal electrodes410and411are formed.

Subsequently, as shown inFIG. 11c, by using an etchant with which the mask85can be etched while leaving the material forming the lead electrode4100, wet etching is performed to remove the mask85, thereby to form the concave portion389in the element-integration surface2102. In the case that, for example, the lead electrode4100is formed of Au and the mask85is formed of NiFe, ferric chloride (FeCl3) solution can be used as the etchant. Thereafter, a laser diode40is placed into the formed concave portion389in such a way that its edge401is parallel with the edge2102a. Further, the laser diode40is aligned in such a way that the light-emission center4000is opposed to the light-receiving end surface352of the waveguide35.

In the placement of the laser diode40on the lead electrode4100, an evaporated film86of AuSn alloy, for example, is deposited on the lead electrode4100, the laser diode40is placed on the evaporated film86, and then the positioning of the laser diode40is performed. After that, the substrate is heated by, for example, a hot plate under a hot wind by a blower up to approximately 200 to 300° C. (degrees centigrade) to fix the laser diode40to the slider substrate210. Lastly, the n-electrode40a, which is the upper surface of the laser diode40, is connected to the terminal electrode411by a solder ball bonding (SBB) method using the solder4111(FIG. 2). There may be used, as the solder4111, a metal including, for example, Sn, Pb, Ag, Cu, Zn, Al, Bi, In or the like.

Thus, the mounting of the laser diode40in the element-integration surface2102is completed. As described above, according to the manufacturing method of the present invention, the laser diode40can be disposed in the element-integration surface2102during a thin-film process in which the waveguide35and so on are formed in the element-integration surface2102. That is, the construction of the optical system can be completed in the stage of a wafer process. As a result, this construction can be relatively facilitated and simplified; thus, mass-productivity in the head manufacturing can be improved.

The method for disposing the laser diode40is not limited to the embodiment shown inFIGS. 11a1to11c. For example, it is possible that the waveguide35and so on are formed, then the entire integration surface2102is covered with the overcoat layer38; thereafter, a predetermined portion on the overcoat layer38are etched with a photolithography method using photoresist masks to form the concave portion389.

Hereinafter, there will be shown the state of the near-field light radiated from a near-field light generating element provided in the thermally-assisted magnetic recording head according to the present invention, by using results of simulation analysis experiments performed as practical examples.

FIGS. 12aand12bshow schematic diagrams illustrating experiment conditions of the simulation analysis experiments performed as practical examples. Here,FIG. 12ais a top view of the experiment system viewed from a position above the head end surface388, andFIG. 12bis a cross-sectional view taken along line D-D ofFIG. 12a.

The simulation analysis experiments were performed by using the three-dimensional Finite-Difference Time-Domain method (FDTD method), which is an electromagnetic field analysis. Referring toFIGS. 12aand12b, the system, by which the simulation analysis examinations were performed, was a rectangular parallelepiped area including: a head part having the waveguide35, the surface plasmon antenna36, and the overcoat layer38covering these elements; and an air layer (refractive index n=1) over the head end surface338of the head part. Incident laser light53was a Gaussian beam with a wavelength λLof 650 nm and having a TM polarization (in which the oscillation direction of electric field of the laser light is perpendicular to a layer surface of the waveguide35; that is, in Z-axis direction). The intensity IINof the laser light53was 1 (V/m)2.

The waveguide35, as shown inFIG. 12b, extended in a curve from the light-receiving end surface87onto which the laser light53was launched, and reached the head end surface388. The waveguide35was formed of TaOX(refractive index n=2.15) and the width WWGand thickness TWGwere 250 nm throughout the waveguide. The surface plasmon antenna36had a width WNFof 160 nm, a thickness TNF1of 80 nm and a length HNFof 1.5 μm, and its constituent material was Ag (the real number part of the refractive index is 0.134, and the imaginary number part is 4.135). The near-field light generating end surface36aof the surface plasmon antenna36, which is positioned within the head end surface388, had a shape of an isosceles triangle with an apex angle θNFof 900 and a height of 80 nm, in the case that an inclination angle θPW, to be described below, was 0° (degree).

The overcoat layer38was formed of Al2O3(refractive index n=1.65), and a portion of the overcoat layer38was the buffering portion sandwiched between the waveguide35and the surface plasmon antenna36. That is, the refractive index of the buffering portion was 1.65. Further, a longitudinal axis36bof the surface plasmon antenna36and the side surface351of the waveguide35in the vicinity of the head end surface388were inclined at an inclination angle θPWfrom the direction perpendicular to the head end surface388toward the light-receiving end surface87, in the cross-section shown inFIG. 12b. The simulation analysis experiments were performed for respective cases in which the inclination angle θPWwas 0° (degree), 30°, 60° and 80°. Here, the case that the inclination angle θPWwas 0° corresponds to the embodiment ofFIG. 4, and the respective cases that the inclination angle θPWwas 30°, 60° and 80° correspond to the embodiment ofFIG. 8d.

Under the experiment conditions described above, there were analyzed the intensity distributions on the head end surface (opposed-to-medium surface)388of the near-field light radiated from the surface plasmon antenna36.

FIGS. 13ato13dshow schematic diagrams illustrating the relationship between the inclination angle θPWand the intensity distribution on the head end surface388of the near-field light radiated from the surface plasmon antenna36.FIGS. 13ato13dshow end surfaces of the surface plasmon antenna36and the waveguide35, which appear on the head end surface388, in respective cases that the inclination angle θPWwas 0°, 30°, 60° and 80°, and further show the intensity distribution (spot) of the near-field light in the vicinity of these end surfaces. Each of the end surfaces on the head end surface388of the waveguide35and the surface plasmon antenna36crosses slantwise the longitudinal axes of the waveguide35and the surface plasmon antenna36, as the inclination angle θPWbecomes larger. Therefore, in the case, each of the end surfaces has a shape extending longer in the track width direction (Y-axis direction). Here, the spot of near-field light on the head end surface388is defined as a distribution area of the near-field light having the intensity of IMAX×e−2(e: the base of natural logarithm) or more, where IMAXindicates the maximum intensity of the near-field light radiated from the surface plasmon antenna36.

According toFIGS. 13aand13b, in respective cases that the inclination angles θPWare 0° and 30°, distributions87and87′ of the near-field light are generated, each having a sufficient intensity for performing thermal assist, at the position of an apex of the near-field light generating end of the surface plasmon antenna. Spots88and88′ including respective distributions87and87′ with the sufficient intensity have a size of 50 nm or less, being confined to a relatively small size.

On the other hand, according toFIGS. 13cand13d, in respective cases that the inclination angles θPWare 60° and 80°, spots89and89′ are generated, each expanding in the track width direction (Y-axis direction). Within these spots89and89′, an area of the near-field light having sufficient intensity for performing thermal assist does not exist. Thus, when the inclination angle θPWexceeds 30°, the spot diameter in the track width direction (Y-axis direction) increases largely. This results from the following reason: As the inclination angle θPWbecomes larger, the propagation edge of the surface plasmon antenna becomes closer to the head end surface388, and therefore a part of the surface plasmon propagating along the propagation edge tends to interact with the magnetic recording layer of a magnetic disk before reaching the end point of the propagation edge on the head end surface388. From this, it is understood that, when the inclination angle θPWexceeds 30°, energy density within the spot of near-field light becomes lowered significantly.

Table 1 shows the relationship between the inclination angle θPWand the spot size of near-field light on the head end surface388, which is obtained from the experiment results ofFIGS. 13ato13d. AndFIG. 14shows a graph illustrating the relationship between the inclination angle θPWand the spot size, which is shown in Table 1. Here, since the head end surface388is parallel with YZ plane, each spot size is presented with both maximum diameters in Z-axis direction (stacking direction) and Y-axis direction (track width direction).

TABLE 1Spot size (nm)Inclination angleDiameter in Z axisDiameter in Y axisθPW(°)directiondirection0253230304860351098040220

According toFIG. 14and Table 1, the spot size of near-field light is confined to a small range in size of 50 nm or less in both Z-axis direction and Y-axis direction when the inclination angle θPWis in the range from 0° to 30°. On the contrary, it is understood that the spot size of near-field light in Y-axis direction increases to a value beyond 100 nm when the inclination angle θPWexceeds 30°.

From the above-described results, it is understood that the inclination angle θPWis preferably 0° or more, and 30° or less. By setting the inclination angle θPWto be 30° or less, the spot size of light (near-field light) in the near-field light generating end surface of the surface plasmon antenna can be made sufficiently smaller; thereby a desired portion on the magnetic recording layer of a magnetic disk can be heated effectively.

As described above, it is understood that there can be provided a thermally-assisted magnetic recording head in which a light source with sufficient power is disposed in the element-integration surface of a slider substrate to improve mass-productivity, and nevertheless light can effectively be guided to a desired position on the opposed-to-medium surface side without using a diffraction optical element. Thus, the present invention can achieve superior thermally-assisted magnetic recording, and contribute to the achievement of higher recording density, for example, exceeding 1 Tbits/in2.

All the foregoing embodiments are by way of example of the present invention only and not intended to be limiting, and many widely different alternations and modifications of the present invention may be constructed without departing from the spirit and scope of the present invention. Accordingly, the present invention is limited only as defined in the following claims and equivalents thereto.