Source: http://www.google.com/patents/US7957099?dq=7,003,515
Timestamp: 2017-01-22 06:17:07
Document Index: 665592496

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Patent US7957099 - Thermally assisted magnetic head with optical waveguide and light shield - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA thermally assisted magnetic head which can realize high-density writing onto magnetic recording media is provided. The thermally assisted magnetic head includes a magnetic head part having a medium-opposing surface and a back face opposing the medium-opposing surface. The magnetic head part has a recording...http://www.google.com/patents/US7957099?utm_source=gb-gplus-sharePatent US7957099 - Thermally assisted magnetic head with optical waveguide and light shieldAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7957099 B2Publication typeGrantApplication numberUS 12/182,738Publication dateJun 7, 2011Filing dateJul 30, 2008Priority dateAug 23, 2007Fee statusPaidAlso published asCN101373596A, CN101373596B, US20090052077Publication number12182738, 182738, US 7957099 B2, US 7957099B2, US-B2-7957099, US7957099 B2, US7957099B2InventorsKosuke Tanaka, Yasuhiro Ito, Koji ShimazawaOriginal AssigneeTdk CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (8), Referenced by (7), Classifications (8), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetThermally assisted magnetic head with optical waveguide and light shield
US 7957099 B2Abstract
A thermally assisted magnetic head which can realize high-density writing onto magnetic recording media is provided.
The thermally assisted magnetic head includes a magnetic head part having a medium-opposing surface and a back face opposing the medium-opposing surface. The magnetic head part has a recording head part, an optical waveguide, and light shields. The optical waveguide extends along the opposing direction of the medium-opposing surface and back face. Each of the light shields extends along the opposing direction of the medium-opposing surface and back face and inhibits laser light from passing between the medium-opposing surface and back face. The optical waveguide and light shields are arranged on a first line when seen from the back face. When seen from the back face, the light shields oppose each other while interposing the first line therebetween and are arranged on a second line substantially orthogonal to the first line.
1. A thermally assisted magnetic head including a magnetic head part having a medium-opposing surface opposing a magnetic recording medium and a back face opposing the medium-opposing surface;
wherein the magnetic head part comprises:
a first optical waveguide extending along the opposing direction of the medium-opposing surface and back face; and
first, second, third, and fourth light shields positioned between the medium-opposing surface and back face and adapted to prevent light from passing between the medium-opposing surface and back face;
wherein the first optical waveguide and the first and second light shields are arranged on a first line when seen from the medium-opposing surface or back face;
wherein the first line is positioned between the third and fourth light shields when seen from the medium-opposing surface or back face; and
wherein the third and fourth light shields are arranged on a second line substantially orthogonal to the first line when seen from the medium-opposing surface or back face.
2. A thermally assisted magnetic head according to claim 1, wherein the first optical waveguide is positioned between the first and second light shields when seen from the medium-opposing surface or back face.
3. A thermally assisted magnetic head according to claim 1, wherein each of the third and fourth light shields extends in a direction along the first line when seen from the medium-opposing surface or back face.
4. A thermally assisted magnetic head according to claim 1, wherein the first, second, third, and fourth light shields are exposed at the back face.
5. A thermally assisted magnetic head according to claim 1, further comprising a second optical waveguide extending along the opposing direction of the medium-opposing surface and back face;
wherein the second optical waveguide is positioned between the third and fourth light shields when seen from the medium-opposing surface or back face.
As hard disk drives have been increasing their recording density, thin-film magnetic heads have been required to further improve their performances. As the thin-film magnetic heads, those of composite type having a structure in which a magnetism detecting device such as a magnetoresistive (M) device and a magnetic recording device such as electromagnetic coil device are laminated have been in wide use, while these devices read/write data signals from/onto magnetic disks which are magnetic recording media.
In general, a magnetic recording medium is a sort of discontinuous body in which magnetic fine particles are assembled, while each magnetic fine particle has a single-domain structure. Here, one recording bit is constituted by a plurality of magnetic fine particles. Therefore, for enhancing the recording density, it is necessary to make the magnetic fine particles smaller, so as to reduce irregularities at boundaries of recording bits. When the magnetic fine particles are made smaller, however, their volume decreases, so that the thermal stability in magnetization may deteriorate, thereby causing a problem. An index of the thermal stability in magnetization is given by KUV/kBT. Here, KU is the magnetic anisotropy energy of a magnetic fine particle, V is the volume of one magnetic fine particle, kB is the Boltzmann constant, and T is the absolute temperature. Making the magnetic fine particles smaller just reduces V, which lowers KUV/kBT by itself, thereby worsening the thermal stability. Though KU may be made greater at the same time as measures against this problem, the increase in KU enhances the coercivity of the magnetic recording medium. On the other hand, the writing magnetic field intensity caused by a magnetic head is substantially determined by the saturated magnetic flux of a soft magnetic material constituting a magnetic pole within the head. Therefore, no writing can be made if the coercivity exceeds a permissible value determined by the limit of writing magnetic field intensity.
As such a thermally assisted magnetic head recording apparatus, Patent Document 1 discloses a thermally assisted magnetic head comprising a slider having a magnetic head part in which an optical waveguide is provided at a position near an electromagnetic coil device in the laminating direction of the magnetic head (bit length direction), and a light source unit in which a light source is provided on a light source supporting substrate different from the slider. In this structure, light emitted from a light-emitting device is introduced into the optical waveguide and then is let out from a light exit surface of the optical waveguide within the medium-opposing surface, so as to heat a magnetic recording medium locally. Subsequently, the electromagnetic coil device applies a writing magnetic field to a local area of the magnetic recording medium having lowered the coercivity by the local heating, so as to perform writing.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2006-185548
For making the thermally assisted magnetic head described in Patent Document 1, it is necessary for the light source unit to be overlaid on and then secured to the surface (back face) of the slider on the side opposite from the medium-opposing surface. In this case, after testing the slider having the magnetic head part and the light source unit independently from each other, the slider and light source unit that have been found nondefective are secured to each other, whereby the thin-film magnetic head can be made with a favorable yield. Since the light source can be provided at a position distanced from the medium-opposing surface while being in the vicinity of the slider, there are substantially no problems concerning decreases in light propagation efficiency, complexity in the structure of the whole apparatus, and the like.
In the case where the slider and the light source unit are made separately from each other as mentioned above, however, it is necessary to accurately align the light source and the optical waveguide with each other when securing the slider and the light source unit to each other. This is because a deterioration in accuracy of alignment leads to a decrease in the heating efficiency of the magnetic recording medium, which may become a big problem when performing thermally assisted magnetic recording.
It is therefore an object of the present invention to provide a thermally assisted magnetic head, a head gimbal assembly, and a hard disk drive, which can realize high-density writing onto magnetic recording media by adjusting the alignment between a light source and an optical waveguide with a very high accuracy.
The thermally assisted magnetic head in accordance with the present invention includes a magnetic head part having a medium-opposing surface opposing a magnetic recording medium and a back face opposing the medium-opposing surface; wherein the magnetic head part comprises an electromagnetic transducer, a first optical waveguide extending along the opposing direction of the medium-opposing surface and back face, and first, second, third, and fourth light shields positioned between the medium-opposing surface and back face and adapted to prevent light from passing between the medium-opposing surface and back face; wherein the first optical waveguide and the first and second light shields are arranged on a first line when seen from the medium-opposing surface or back face; wherein the first line is positioned between the third and fourth light shields when seen from the medium-opposing surface or back face; and wherein the third and fourth light shields are arranged on a second line substantially orthogonal to the first line when seen from the medium-opposing surface or back face.
In the thermally assisted magnetic head in accordance with the present invention, the first optical waveguide and the first and second light shields are arranged on the first line when seen from the medium-opposing surface or back face. In the thermally assisted magnetic head in accordance with the present invention, when seen from the medium-opposing surface or back face, the third and fourth light shields oppose each other while interposing the first line therebetween and are arranged on the second line substantially orthogonal to the first line. Therefore, a light source is initially arranged on the back face side and successively moved (scanned) while emitting light so that the emitted light irradiates the third light shield and then the fourth light shield, and how the intensity of light transmitted through the magnetic head part or the like changes is detected on the medium-opposing surface side, whereby a position between the third and fourth light shields can be specified. Subsequently, while emitting light, the light source is successively moved (scanned) along a line which passes the specified position between the third and fourth light shields and is substantially orthogonal to the second line, i.e., along the first line, and how the intensity of light transmitted through the magnetic head part or the like changes is detected on the medium-opposing surface side, whereby the position of the first optical waveguide can be specified. Hence, the position of the first optical waveguide can be specified from two different directions, whereby the alignment between the light source and the first optical waveguide can be adjusted with a very high accuracy. This can realize high-density writing onto recording media.
Preferably, the first optical waveguide is positioned between the first and second light shields when seen from the medium-opposing surface or back face. In this case, when the light source is successively moved (scanned) along the first line while emitting light, and the intensity of light transmitted through the magnetic head part or the like changes is detected on the medium-opposing surface side, the emitted light successively irradiates the first light shield, first optical waveguide, and second light shield, so that the detected amount such as light intensity successively becomes small, large, and small, whereby the position of the first optical waveguide can be specified easily with a higher accuracy.
Preferably, each of the third and fourth light shields extends in a direction along the first line when seen from the medium-opposing surface or back face. This makes it possible to specify a position between the third and fourth light shields even when the light source is moved roughly to some extent, whereby the position of the first optical waveguide can be specified more easily.
Preferably, the first, second, third, and fourth light shields are exposed at the back face. This allows each light shield to securely block the light emitted from the light source, since the light has such a property as to expand in a direction intersecting its advancing direction while advancing. As a result, the position of the first optical waveguide can be specified with a higher accuracy.
Preferably, the magnetic head part further comprises a second optical waveguide extending along the opposing direction of the medium-opposing surface and back face, while the second optical waveguide is positioned between the third and fourth light shields when seen from the medium-opposing surface or back face.
The hard disk in accordance with the present invention comprises the head gimbal assembly in accordance with the present invention and a magnetic recording medium opposing the medium-opposing surface. The present invention can provide a thermally assisted magnetic head, a head gimbal assembly, and a hard disk drive, which can realize high-density writing onto magnetic recording media by adjusting the position of a light source with a very high accuracy.
FIG. 5 is a partly enlarged view of a magnetic pole end part and optical waveguides as seen from the medium-opposing surface side;
FIG. 6 is a perspective view showing a main part of the thermally assisted magnetic head;
FIG. 7 is a perspective view mainly showing optical waveguides and light shields;
FIG. 8 is a perspective view showing a laser diode;
FIG. 9 is a diagram showing a circuit configuration of the thermally assisted magnetic head;
FIG. 10 is a view showing a step of manufacturing the thermally assisted magnetic head in accordance with an embodiment;
FIG. 11 is a view showing a step subsequent to that of FIG. 10;
FIG. 12 is a view showing a step subsequent to that of FIG. 11; and
(a) of FIG. 13 is a partly enlarged view of the optical waveguides and light shields as seen from the back face of the magnetic head part,
(b) of FIG. 13 is a chart showing how the output of a photodetector changes when a light source unit moves in the direction of arrow A, and
(c) of FIG. 13 is a chart showing how the output of the photodetector changes when the light source unit moves in the direction of arrow B.
Preferred embodiments of the present invention will be explained with reference to the drawings. In the explanation, the same constituents or those having the same functions will be referred to with the same numerals or letters while omitting their overlapping descriptions. For easier viewing of the drawings, ratios of dimensions within and among the constituents in the drawings are arbitrary.
The structure of the thermally assisted magnetic head 21 will now be explained with reference to FIGS. 3 to 7. The thermally assisted magnetic head 21 comprises a slider 22 having a slider substrate 220 and a magnetic head part 32 for writing and reading data, and a light source unit 23 having a light source supporting substrate 230 and a laser diode (light-emitting device) 40 acting as a light source for thermally assisted magnetic recording. The slider substrate 220 and the light source supporting substrate 230 are firmly attached to each other by an adhesive 44 such as UV-curable epoxy resin or UV curable acrylic resin in a state where a back face 2201 of the slider substrate 220 and a bonding surface 2300 of the light source supporting substrate 230 are in contact with each other (see FIG. 4).
The slider substrate 220 in the slider 22 has a planar form as shown in FIG. 3. The medium-opposing surface S of the slider substrate 220 is processed into a predetermined form such that the thermally assisted magnetic head 21 can attain an appropriate flying height. The slider substrate 220 can be formed by AlTiC (Al2O3·TiC) or the like which is conductive.
The magnetic head part 32 in the slider 22 is provided on an integration surface 2202 which is a side face adjacent to the medium-opposing surface S and back face 2201 and substantially perpendicular to the medium-opposing surface S of the slider substrate 220. The magnetic head part 32 comprises a reading head part 33 having an M device 332, a recording head part 34 as an inductive electromagnetic transducer for writing, optical waveguides 35A, 35B, 35C provided between the reading head part 33 and recording head part 34, a near-field-light-generating part (plasmon probe) 36 for generating near-field light for heating a recording layer part of the magnetic disk 10, light shields 39A, 39B, 39C, 39D, 39E, 39F, and an insulating layer 38 formed on the integration surface so as to cover the reading head part 33, recording head part 34, optical waveguides 35A to 35C, near-field-light-generating part 36, and light shields 39A to 39F. As shown in FIG. 4, the reading head part 33 is constructed by laminating a lower magnetic shield layer 330 also acting as a lower electrode, an MR device 332, and an upper magnetic shield layer 334 also acting as an upper electrode in this order on the slider substrate 220. A pair of bias application layers IM made of a hard magnetic material (see FIG. 6) is formed on both sides in the track width direction of the MR device 332 by way of the insulating layer 38.
The MR device 332 has a multilayer structure including a free layer (not depicted) and is arranged on the medium-opposing surface S side so as to be exposed at the medium-opposing surface S. Utilizing a magnetoresistive effect, the MR device 332 detects a change in a magnetic field inputted from the magnetic disk 10, thereby reading magnetic information recorded on the magnetic disk 10. GMR (giant magnetoresistive) devices utilizing a giant magnetoresistive effect yielding a high magnetoresistance change ratio, AMR (anisotropic magnetoresistive) devices utilizing an anisotropic magnetoresistive effect, TMR (tunneling magnetoresistive) devices utilizing a magnetoresistive effect occurring at a tunneling junction, CPP (Current Perpendicular to Plane)-GMR devices, and the like may be used in place of the M device 332.
Preferably, the magnetic pole end part 340 a is made smaller than the other parts in terms of the width in the track width direction and the thickness in the laminating direction (horizontal direction in FIG. 4). As a result, a fine, strong writing magnetic field adapted to higher recording density can be generated. Specifically, it will be preferred if the leading end of the magnetic pole end part 340 a is tapered such as to form an inverted trapezoid in which a side on the leading side, i.e., the slider substrate 220 side, is shorter than a side on the trailing side. Namely, each of the end faces of the magnetic pole end part 340 a is provided with a bevel angle θ so as not to cause unnecessary writing and the like in adjacent tracks under the influence of skew angles generated when driven by a rotary actuator. The bevel angle θ is about 15°, for example. The writing magnetic field is mainly generated near the longer side on the trailing side, while the length of the longer side determines the width of a writing track in the case of magnetic dominant recording.
Here, the main magnetic pole layer 340 is preferably constituted by an alloy made of two or three elements among Ni, Fe, and Co, an alloy manly composed of them and doped with a predetermined element, or the like. The main magnetic pole layer 340 can be formed by frame plating, sputtering, or the like. The thickness of the magnetic pole end part 340 a can be set to about 0.01 μm to 0.5 μm, for example, while the thickness of the main magnetic pole layer 340 in the part other than the magnetic pole end part 340 a can be set to about 0.5 μm to 3.0 μm, for example. The track width can be set to about 100 nm, for example.
As shown in FIG. 4, the optical waveguide 35A is arranged between the reading head part 33 and recording head part 34, and extends from the medium-opposing surface S to the back face 32 a (the surface of the magnetic head part 32 on the side opposite from the medium-opposing surface S) so as to become parallel to the integration surface 2202. As shown in FIG. 4, the optical waveguide 35A is constituted by a core part 35 a extending from the medium-opposing surface S to the vicinity of the back face 32 a, and a noncore part 35 b extending from the end face of the core part 35 a on the medium-opposing surface S side to the back face 32 a. Therefore, the end face of the core part 35 a on the medium-opposing surface S side (the end face of the optical waveguide 35A on the medium-opposing surface S side) is exposed at the medium-opposing surface S and forms a light exit surface 353A from which laser light generated by the laser diode 40 is emitted (see FIGS. 4 and 6).
The end face of the noncore part 35 b on the back face 32 a side (the end face of the optical waveguide 35A on the side opposite from the light exit surface 353A) is exposed at the back face 32 a and forms a light entrance surface 354A on which the laser light generated by the laser diode 40 is incident (see FIGS. 4 and 6). Though the end face of the core part 35 a on the back face 32 a side is not exposed at the back face 32 a, the laser light from the laser diode 40 propagates through the noncore part 35 b (between the back face 32 a and the end face of the core part 35 a on the back face 32 a side) and the core part 35 a, before being emitted from the light exit surface 353A.
As shown in FIG. 6, the core part 35 a is mainly formed like a substantially rectangular plate, while both corner portions in the track width direction of its end part on the medium-opposing surface S side are chamfered. Therefore, the end part of the core part 35 a on the medium-opposing surface S side reduces its width in the track width direction toward the medium-opposing surface S. This makes it possible for the core part 35 a (optical waveguide 35A) to converge the laser light from the laser diode 40 at the center part in the track width direction. Here, the back face 32 a is substantially parallel to the medium-opposing surface S.
Returning to FIG. 4, the core part 35 a is covered with the insulating layer 38 except for the light exit surface 353A. The insulating layer 38 is constituted by a material having a refractive index lower than that of the material constituting the core part 35 a, so as to function as a cladding for the core part 35 a. Namely, a part of the insulating layer 38 forms the noncore part 35 b. Preferably, the noncore part 35 b has a length H (see FIG. 6) set to about 0.5 μm to 20 Jim in the dept direction with respect to the medium-opposing surface S.
When the insulating layer 38 as a cladding is formed by SiO2 (n =1.5), the core part 35 a can be formed by Al2O3 (n=1.63). When the insulating layer 38 is formed by Al2O3, the core part 35 a can be formed by Ta2O5 (n=2.16), Nb2O5 (n=2.33), TiO (n=23 to 2.55), or TiO2 (n =2.3 to 2.55). When the core part 35 a is constituted by such a material, the propagation loss of laser light is reduced not only by favorable optical characteristics inherent in the material but also by the fact that the total reflection condition is attained at the interface.
As shown in FIGS. 4 and 6, an interdevice shield layer 148 formed by a material similar to that of the lower and upper shield layers 330 and 334 is arranged between the reading head part 33 and optical waveguide 35A. The interdevice shield layer 148 blocks the magnetic field generated in the recording head part 34 so as to keep the M device 332 from sensing it, thereby functioning to suppress exogenous noise at the time of reading by the MR device 332. A backing coil part may further be formed between the reading head part 33 and optical waveguide 35A.
As shown in FIGS. 4 to 6, the near-field-light-generating part 36 is a planar member arranged at the light exit surface 353A of the optical waveguide 35. The near-field-light-generating part 36 is positioned at a location where laser light having a high intensity is emitted in the light exit surface 353A, and buried in the core part 35 a such as to expose its end face at the light exit surface 353A.
As shown in FIGS. 5 and 6, the near-field-light-generating part 36 exhibits a triangular form when seen from the medium-opposing surface S, and is constituted by a conductive material (e.g., Au, Ag, Al, Cu, Pd, Pt, Rn, or Ir or an alloy combining such elements). A base 36 d of the near-field-light-generating part 36 is arranged parallel to the integration surface 2202 of the slider substrate 220, i.e., parallel to the track width direction, while a vertex 36 v of the near-field-light-generating part 36 opposing the base 36 d is arranged closer to the main magnetic pole layer 340 than is the base 36 d. The form of the near-field-light-generating part 36 is preferably an isosceles triangle in which two base angles at both ends of the base 36 d are equal.
When thus configured near-field-light-generating part 36 is irradiated with the laser light from the laser diode 40, electrons in the metal constituting the near-field-light-generating part 36 are subjected to plasma oscillations, so that electric fields are converged near the vertex 36 v, whereby near-field light is generated so as to be directed from near the vertex 36 v to a recording area R of the magnetic disk 10 (see FIG. 6). The spread of near-field light is about the radius of the near-field-light-generating part 36 in the vicinity of the vertex 36 v, whereby the emitted light can simulatively be narrowed to a diffraction limit or less if the radius near the vertex 36 v is not greater than the track width.
On the other hand, as shown in FIGS. 3 and 7, the optical waveguides 35B, 35C are arranged so as to oppose each other while interposing the optical waveguide 35A therebetween in the track width direction when seen from the back face 32 a (or the medium-opposing surface S), and extend from the medium-opposing surface S to the back face 32 a so as to become parallel to the integration surface 2202. The optical waveguides 35B, 35C are totally constituted by the same material as that of the core part 35 a of the optical waveguide 35A. Hence, the end faces of the optical waveguides 35B, 35C on the medium-opposing surface S side are exposed at the medium-opposing surface S, and form light exit surfaces 353B, 353C from which light generated by a light source positioned on the back face 32 a is emitted (see FIG. 7).
The end faces of the optical waveguides 35B, 35C on the back face 32 a side are exposed at the back face 32 a, and form light entrance surfaces 354B, 354C on which the light generated by the light source positioned on the back face 32 a is incident (see FIG. 7). Unlike the optical waveguide 35A, the optical waveguides 35B, 35C are not provided with the near-field-light-generating part 36.
Except for the light exit surfaces 353B, 353C and light entrance surfaces 354B, 354C, the optical waveguides 35B, 35C are covered with the insulating layer 38 (see FIG. 3). Therefore, the insulating layer 38 also functions as a cladding for the light entrance surfaces 354B, 354C.
The light shields 39A to 39F reflect, absorb, or scatter light, for example, so as to prevent the light from passing between the medium-opposing surface S and back face 32 a (block the light). The light shields 39A to 39F are constituted by a metal material such as Cu, Ni, Fe, or Au or a magnetic material such as permalloy, for example, and can be formed by plating, for example.
As shown in FIGS. 3 and 7, the light shields 39A to 39F extend from the medium-opposing surface S to the back face 32 a so as to become parallel to the integration surface 2202 (i.e., are positioned between the medium-opposing surface S and back face 32 a). The end faces of the light shields 39A to 39F on the back face 32 a side are exposed at the back face 32 a, while the end faces of the light shields 39A to 39F on the medium-opposing surface S side are not exposed at the medium-opposing surface S.
When seen from the back face 32 a (or the medium-opposing surface S), the light shields 39A, 39B are arranged between the optical waveguides 35B, 35C so as to oppose each other while interposing the optical waveguide 35A therebetween in the track width direction. When seen from the back face 32 a (or the medium-opposing surface S), the light shields 39C, 39D are arranged so as to oppose each other while interposing the optical waveguide 35B therebetween. When seen from the back face 32 a (or the medium-opposing surface S), the light shields 39E, 39F are arranged so as to oppose each other while interposing the optical waveguide 35C therebetween.
Therefore, when seen from the back face 32 a (or the medium-opposing surface S), the optical waveguides 35A, 35B, 35C and light shields 39A, 39B are arranged on the same line (on a first line L1) (see FIG. 7). When seen from the back face 32 a (or the medium-opposing surface S), the optical waveguide 35B and light shields 39C, 39D are arranged on a second line L2 substantially orthogonal to the first line L1 (the line on which the optical waveguides 35A, 35B, 35C and light shields 39A, 39B are arranged) (see FIG. 7). When seen from the back face 32 a (or the medium-opposing surface S), the optical waveguide 35C and light shields 39E, 39F are arranged on a third line L3 substantially orthogonal to the first line L1 (the line on which the optical waveguides 35A, 35B, 35C and light shields 39A, 39B are arranged) (see FIG. 7). The light shields 39C to 39F and optical waveguides 35B, 35C extend in directions along the first line L1.
Returning to FIG. 3, the magnetic head part 32 in the slider 22 further comprises a pair of electrode pads 371 (see also FIG. 6) connected to input and output terminals of the reading head part 33, respectively, for signal terminals; a pair of electrode pads 373 (see also FIG. 6) connected to both ends of the recording head part 34, respectively, for signal terminals; and a grounding electrode pad 375 (see also FIG. 4) electrically connected to the slider substrate 220 through a via hole 375 a. The electrode pads 371, 373, 375 are formed on the exposed surface of the insulating layer 38. The electrode pad 375 is connected to the electrode pad 274 of the flexure 201 by a bonding wire (not depicted). Therefore, the potential of the slider substrate 220 is adjusted by the electrode pad 274 to the ground potential, for example.
As shown in FIG. 3, the light source supporting substrate 230 in the light source unit 23 exhibits a planar form. As shown in FIG. 4, the light source supporting substrate 230 has a heat insulating layer 230 a formed by alumina or the like and a conductor layer 230 b formed by AlTiC (Al2O3·TiC) or the like which is conductive. The heat insulating layer 230 a is bonded to the back face 2201 of the slider substrate 220 and acts as the bonding surface 2300 of the light source supporting substrate 230. An insulating layer 41 formed by an insulating material such as alumina is provided on a device forming surface 2303 which is a side face adjacent to the bonding surface 2300.
As shown in FIG. 4, the laser diode 40 in the light source unit 23 is firmly attached onto the electrode pad 47 by a solder layer 42 made of a conductive solder material such as Au—Sn, so as to be electrically connected to the electrode pad 47. Namely, a part of the electrode pad 47 is covered with the laser diode 40, while the laser diode 40 is supported by the light source supporting substrate 230 through the electrode pad 47. More specifically, the laser diode 40 is supported by the light source supporting substrate 230 such that the laser light emitted from a light exit end 400, which will be explained later, is introduced to the optical waveguide 35A (see FIGS. 3 and 4).
The laser diode 40 is also supported by the light source supporting substrate 230 such that the light exit end 400 is located closer to the magnetic head part 32 than is the back face 2201 of the slider substrate 220 (see FIGS. 3 and 4). The laser diode 40 can be supported as such, since the back face 2201 of the slider substrate 220 projects more outward than the back face 32 a of the magnetic head part 32 does as mentioned above. This inhibits the laser light emitted from the laser diode 40 from being scattered on the light source supporting substrate 230 before reaching the optical waveguide 35A, whereby the magnetic disk 10 can be heated sufficiently.
The laser diode 40 may have the same structure as one typically used for optical disk storage. For example, as shown in FIG. 8, the laser diode 40 has a structure in which an n-electrode 40 a, an n-GaAs substrate 40 b, an n-InGaAlP cladding layer 40 c, a first InGaAlP guide layer 40 d, an active layer 40 e made of a multiple quantum well (InGaP/InGaAlP) or the like, a second InGaAlP guide layer 40 f, a p-InGaAlP cladding layer 40 g, an *n-GaAs current blocking layer 40 h, a p-GaAs contact layer 40 i, and a p-electrode 40 j are successively laminated. Reflective films 50, 51 made of SiO2, Al2O3, or the like for pumping oscillations by total reflection are formed in front and rear of a cleavage surface of the multilayer structure. One reflective film 50 is provided with an opening 50 a at a position corresponding to the active layer 40 e, while an area corresponding to the opening 50 a in the surface formed with the reflecting film 50 is a light exit end 400 from which the laser light is emitted. When a voltage is applied to thus constructed laser diode 40 in the thickness direction, the laser light is emitted from the light exit end 400.
The n-electrode 40 a of the laser diode 40 is secured to the electrode pad 47 by the solder layer 42 made of AuSn or the like. Here, the light exit end (light exit surface) 400 of the laser diode 40 faces down (in the—Z direction) in FIG. 4 (so as to be parallel to the bonding surface 2300), thereby opposing the light entrance surface 354A of the optical waveguide 35A. For securing the laser diode 40 in practice, for example, a vapor deposition film of an AuSn alloy having a thickness of about 0.7 μm to 1 μm is formed on the surface of the electrode pad 47, the laser diode 40 is mounted thereon, and then heating to about 200° C. to 300° C. is effected by a hot plate or the like under a hot air blower.
When soldering with the above-mentioned AuSn alloy, the light source unit 23 is heated to a high temperature around 300° C., for example. In the thermally assisted magnetic head 21 in accordance with this embodiment, the light source unit 23 is manufactured separately from the slider 22, whereby the magnetic head part 32 of the slider 22 is not adversely affected by the high temperature.
The circuit configuration of the thermally assisted magnetic head 21 will now be explained with reference to FIG. 9.
One of leads constituting the wiring member 203 is electrically connected to the cathode of the laser diode 40 through the electrode pads 247, 47, while another lead is electrically connected to the anode of the laser diode 40 through the electrode pads 248, 48. When a driving current is supplied between the electrode pads 247, 248, the laser diode 40 emits light. This light irradiates the recording area R (see FIG. 6) of the magnetic disk 10 by way of the optical waveguide 35A and medium-opposing surface S.
Another pair of leads constituting the wiring member 203 are connected to both ends of the recording head part 34 through the electrode pads 237, bonding wires BW, and electrode pads 373. When a voltage is applied between the pair of electrode pads 237, the recording head part 34 is energized, whereby a writing magnetic field occurs. In the thermally assisted magnetic head 21, the laser light emitted from the laser diode 40 is incident on the light entrance surface 354A of the optical waveguide 35A and exits from the light exit surface 353A provided on the medium-opposing surface S, so as to irradiate the recording area R (see FIG. 6) of the magnetic disk 10. Here, temperature rises in the recording area R of the magnetic disk 10 opposing the medium-opposing surface S, whereby the coercivity of the recording area R decreases temporarily. Therefore, when the recording head part 34 is energized in this coercivity decreasing period, so as to generate a writing magnetic field, information can be written in the recording area R.
A method of manufacturing the thermally assisted magnetic head 21 will now be explained with reference to FIGS. 10 to 13.
First, the slider 22 having the above-mentioned structure and the light source unit 23 having the above-mentioned structure are manufactured. Subsequently, the slider 22 and light source unit 23 that are considered nondefective are aligned with each other.
Specifically, as shown in FIG. 10, a photodetector DT such as photodiode is arranged on the medium-opposing surface S side of the slider 22. Then, a voltage is applied between the electrode pads 47, 48, so that the laser diode 40 emits light in a state where the back face 2201 of the slider substrate 220 and the bonding surface 2300 of the light source supporting substrate 230 are overlaid on each other, the light source unit 23 is moved (scanned) at a predetermined speed in the direction of arrow A (see FIG. 10 and (a) of FIG. 13) while the laser diode 40 keeps emitting the laser light so that the light shield 39D, optical waveguide 35B, and light shield 39C are successively irradiated with the laser light generated by the laser diode 40, and how the intensity of light transmitted from the back face 32 a to the medium-opposing surface S or the like changes is detected by the photodetector DT.
(b) of FIG. 13 shows the output of the photodetector DT at this time. As shown in (b) of FIG. 13, the output of the photodetector DT becomes the highest, substantially 0, and a predetermined level when the laser light irradiates the insulating layer 38, any of the light shield 39C, 39D, and the optical waveguide 35B, respectively. Therefore, a position between the light shields 39C, 39D, i.e., the position of the optical waveguide 35B can be specified. The reason why the output of the photodetector DT is higher when the laser light irradiates the insulating layer 38 than when irradiating the optical waveguide 35B lies in the facts that the optical waveguide 35B has a refractive index higher than that of the insulating layer 38 and that the laser light decays during when propagating through the optical waveguide 35B while repeating total reflection.
Next, a voltage is applied between the electrode pads 47, 48, so that the laser diode 40 emits light in a state where the back face 2201 of the slider substrate 220 and the bonding surface 2300 of the light source supporting substrate 230 are overlaid on each other, the light source unit 23 is moved (scanned) at a predetermined speed in the direction of arrow B (seen FIG. 11 and (a) of FIG. 13) while the laser diode 40 keeps emitting the laser light so that the gap (optical waveguide 35B) between the light shields 39C and 39D, light shield 39B, optical waveguide 35A, light shield 39A, and optical waveguide 35C are successively irradiated with the laser light generated by the laser diode 40, and how the intensity of light transmitted from the back face 32 a to the medium-opposing surface S or the like changes is detected by the photodetector DT.
(c) of FIG. 13 shows the output of the photodetector DT at this time. As shown in (c) of FIG. 13, the output of the photodetector DT becomes the highest, substantially 0, and a predetermined level when the laser light irradiates the insulating layer 38, any of the light shields 39A, 39B, and any of the optical waveguides 35A to 35C, respectively. Therefore, a position between the light shields 39A, 39B, i.e., the position of the optical waveguide 35A can be specified. The reason why the output of the photodetector DT is higher when the laser light irradiates the optical waveguides 35B, 35C than when irradiating the optical waveguide 35A lies in the facts that the near-field-light-generating part 36 is provided at the light exit surface 353A of the optical waveguide 35A and that the light emitted from the light exit surface 353A of the optical waveguide 35A is near-field light, which is not a traveling wave and is hard to detect.
After the position of the optical waveguide 35A is thus specified, a UV-curable adhesive 44 a which becomes the adhesive 44 when cured is applied to the back face 2201 of the slider substrate 220 and/or the bonding surface 2300 of the light source supporting substrate 230. Examples of the UV-curable adhesive 44 a include UV-curable epoxy resins and UV-curable acrylic resins. The slider 22 and the light source unit 23 are aligned with each other such that the light exit end 400 of the laser diode 40 overlies the optical waveguide 35A when seen from the back face 32 a (or the medium-opposing surface S). Subsequently, at this position, the back face 2201 of the slider substrate 220 and the bonding surface 2300 of the light source supporting substrate 230 are overlaid on each other.
Thereafter, the UV-curable adhesive 44 a is irradiated with UV rays from the outside, so as to be cured, whereby the slider 22 and the light source unit 23 are bonded to each other. This forms the thermally assisted magnetic head 21.
At the time of a writing or recording action, the thin-film magnetic head 21 hydrodynamically floats by a predetermined flying height above the surface of the rotating magnetic disk 10. Here, the ends of the reading head part 33 and recording head part 34 on the medium-opposing surface S side oppose the magnetic disk 10 with a minute spacing therefrom, so as to effect reading and writing by sensing and applying a data signal magnetic field, respectively.
When writing a data signal, the laser light propagated from the light source unit 23 through the optical waveguide 35A reaches the near-field-light-generating part 36, whereby near-field light is generated by the near-field-light-generating part 36. This near-field light enables thermally assisted magnetic recording.
In the foregoing embodiment, the optical waveguide 35B, light shield 39B, optical waveguide 35A, light shield 39A, and optical waveguide 35C are successively arranged on the same line L1 when seen from the back face 32 a (or the medium-opposing surface S). Also, in this embodiment, the light shields 39C, 39D are arranged such as to oppose each other while interposing the line L1 (optical waveguide 35B) therebetween (i.e., the light shield 39C, optical waveguide 35B, and light shield 39D are successively arranged on the same line L2) when seen from the back face 32 a (or the medium-opposing surface S). Further, in this embodiment, the light shields 39E, 39F are arranged such as to oppose each other while interposing the line L1 (optical waveguide 35C) therebetween (i.e., the light shield 39F, optical waveguide 35C, and light shield 39E are successively arranged on the line L3) when seen from the back face 32 a (or the medium-opposing surface S). Therefore, the light source unit 23 is moved (scanned) while the laser diode 40 positioned on the back face 32 a side emits laser light such that the laser light emitted from the laser diode 40 initially irradiates the light shield 39D and then the light shield 39C, and how the intensity of laser light transmitted from the back face 32 a to the medium-opposing surface S (the laser light transmitted through the magnetic head part 32) or the like changes is detected by the photodetector DT positioned on the medium-opposing surface S side, whereby a position between the light shields 39C, 39D (the position of the optical waveguide 35B) can be specified. Subsequently, the light source unit 23 is moved (scanned) while the laser diode 40 emits laser light such that the laser light emitted from the laser diode 40 passes the specified position (optical waveguide 35B) between the light shields 39C, 39D and travels along the line L1, and how the intensity of laser light transmitted from the back face 32 a to the medium-opposing surface S (the laser light transmitted through the magnetic head part 32) or the like changes is detected by the photodetector DT positioned on the medium-opposing surface S side, whereby the position of the optical waveguide 35A can be specified. Hence, the position of the optical waveguide 35A can be specified from two different directions, whereby the alignment between the laser diode 40 and the optical waveguide 35A can be adjusted with a very high accuracy. This can realize high-density writing onto the magnetic disk 10.
In this embodiment, the light shields 39A to 39F are exposed at the back face 32 a. This allows each light shield to securely block the laser light emitted from the laser diode 40, since the light has such a property as to expand in a direction intersecting its advancing direction while advancing. As a result, the position of the optical waveguide 35A can be specified with a higher accuracy.
Though a preferred embodiment of the present invention is explained in detail in the foregoing, the present invention is not limited to the above-mentioned embodiment. For example, though the near-field-light-generating part 36 has a triangular form in the above-mentioned embodiment, the vertex 36 v may be flattened to yield a trapezoidal form. Also employable is a so-called “bowtie” structure in which a pair of triangular or trapezoidal plates are arranged such that their vertexes or shorter sides oppose each other while being separated by a predetermined distance therebetween. In this “bowtie” structure, electric fields converge strongly at its center part.
As the near-field-light-generating part 36, a minute opening smaller than the wavelength of laser light may be provided on the medium-opposing surface S side of the optical waveguide 35A.
The end face of the core part 35 a on the medium-opposing surface S side is not required to be exposed at the medium-opposing surface S as long as the intensity of the light emitted from the optical waveguide 35A can be maximized.
Though the optical waveguides 35B, 35C are totally constituted by the same material as that of the core part 35 a of the optical waveguide 35A, the parts of the optical waveguides 35B, 35C corresponding to the core part 35 a may be not exposed at the back face 32 a or not exposed at the medium-opposing surface S as with the optical waveguide 35A. The magnetic head part 32 may be free of the optical waveguides 35B, 35C.
The light shields 39A to 39F are not required to be exposed at the back face 32 a and may be exposed at the medium-opposing surface S.
As long as the optical waveguide 35A and light shields 39A, 39B are arranged on the same line L1, the light shields 39A, 39B are not required to be arranged so as to oppose each other while interposing the optical waveguide 35A therebetween.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS7538978 *Dec 28, 2005May 26, 2009Tdk CorporationHeat assisted magnetic recording head and heat assisted magnetic recording apparatus for heating a recording region in a magnetic recording medium during magnetic recordingUS7609480 *Jun 30, 2006Oct 27, 2009Seagate Technology LlcHeat-assisted magnetic recording headUS7710686 *Dec 22, 2006May 4, 2010Samsung Electronics Co., Ltd.Heat-assisted magnetic recording head and method of manufacturing the sameUS7729085 *Apr 4, 2006Jun 1, 2010Hitachi Global Storage Technologies Netherlands B.V.Thermally assisted recording of magnetic media using an optical resonant cavityUS7791838 *Apr 26, 2007Sep 7, 2010Tdk CorporationMagnetic head apparatus and magnetic recording and reproducing apparatusUS20040081030 *Mar 31, 2003Apr 29, 2004Dong-Seob JangHybrid writing and reading head to record data with high densityUS20060187564Dec 28, 2005Aug 24, 2006Tdk CorporationHeat assisted magnetic recording head and heat assisted magnetic recording apparatusJP2006185548A Title not available* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS8406092 *Sep 28, 2010Mar 26, 2013Tdk CorporationThermally-assisted magnetic recording headUS8873352Mar 12, 2014Oct 28, 2014Seagate Technology LlcLight mitigation layer between write pole and waveguideUS9065236Apr 29, 2011Jun 23, 2015Seagate TechnologyMethod and apparatus for aligning a laser diode on a sliderUS9099145Mar 17, 2014Aug 4, 2015Western Digital (Fremont), LlcHigh contrast alignment markerUS9315008Aug 19, 2013Apr 19, 2016Western Digital Technologies, Inc.Method and apparatus for aligning an illumination unit to a slider for a magnetic recording deviceUS9373348Nov 22, 2013Jun 21, 2016Seagate Technology LlcStorage medium with layer(s) for enhanced heatingUS20120075966 *Sep 28, 2010Mar 29, 2012Tdk CorporationThermally-assisted magnetic recording head* Cited by examinerClassifications U.S. Classification360/125.74International ClassificationG11B5/02Cooperative ClassificationG11B2005/0005, G11B5/02, G11B5/314, G11B2005/0021European ClassificationG11B5/02, G11B5/31D8A2Legal EventsDateCodeEventDescriptionJul 30, 2008ASAssignmentOwner name: TDK CORPORATION, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TANAKA, KOSUKE;ITO, YASUHIRO;SHIMAZAWA, KOJI;REEL/FRAME:021320/0194Effective date: 20080716Nov 5, 2014FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services