Patent Application
20140233361
1. Field of the Invention
The invention relates to a thermally-assisted magnetic recording head used in thermally-assisted magnetic recording in which near-field light is applied to lower a coercivity of a magnetic recording medium so as to perform recording of information, and to a method of manufacturing the thermally-assisted magnetic recording head.
2. Description of Related Art
A magnetic disk unit has been used for writing and reading magnetic information (hereinafter, simply referred to as information). The magnetic disk unit includes, in a housing thereof for example, a magnetic disk in which information is stored, and a magnetic recording reproducing head that records information into the magnetic disk and reproduces information stored in the magnetic disk. The magnetic disk is supported by a rotary shaft of a spindle motor, which is fixed to the housing, and rotates around the rotary shaft. On the other hand, the magnetic recording reproducing head is formed on a side surface of a magnetic head slider provided on one end of a suspension, and includes a magnetic recording element and a magnetic reproducing element that have an air bearing surface (ABS) facing the magnetic disk. In particular, an MR element exhibiting magnetoresistive (MR) effect is generally used as the magnetic reproducing element. The other end of the suspension is attached to an end of an arm pivotally supported by a fixed shaft installed upright in the housing.
When the magnetic disk unit is in a stationary state, namely, when the magnetic disk does not rotate and remains stationary, the magnetic recording reproducing head is not located over the magnetic disk and is pulled off to the outside (unload state). When the magnetic disk unit is in a driven state and the magnetic disk starts to rotate, the magnetic recording reproducing head is changed to a state where the magnetic recording reproducing head is moved to a predetermined position over the magnetic disk together with the suspension (load state). When the number of rotation of the magnetic disk reaches a predetermined number, the magnetic head slider is stabilized in a state of slightly floating over the surface of the magnetic disk due to the balance of positive pressure and negative pressure. Thus, information is accurately recorded and reproduced.
In recent years, along with a progress in higher recording density (higher capacity) of the magnetic disk, improvement in performance of the magnetic recording reproducing head and the magnetic disk has been demanded. The magnetic disk is a discontinuous medium including collected magnetic microparticles, and each magnetic microparticle has a single-domain structure. In the magnetic disk, one recording bit is configured of a plurality of magnetic microparticles. Since the asperity of a boundary between adjacent recording bits needs to be made small in order to increase the recording density, it is necessary to reduce a size of the magnetic microparticles. However, when the magnetic microparticles are made small in size, thermal stability of the magnetization of the magnetic microparticles is disadvantageously lowered with decreasing volume of the magnetic microparticles. To solve this issue, it is effective to increase anisotropy energy of the magnetic microparticle. However, increasing the anisotropy energy of the magnetic microparticle leads to increase in the coercivity of the magnetic disk. As a result, difficulty occurs in the existing magnetic head in that the information recording becomes difficult.
As a method to solve the above-described difficulty, a method referred to as a so-called thermally-assisted magnetic recording has been proposed. In this method, a magnetic recording medium having large coercivity is used, and when information is written, heat is applied together with the magnetic field to a section of the magnetic recording medium where the information is to be written to increase the temperature and lower the coercivity of that section, thereby writing the information. Hereinafter, the magnetic head used in the thermally-assisted magnetic recording is referred to as a thermally-assisted magnetic recording head.
In performing the thermally-assisted magnetic recording, near-field light is generally used for applying heat to a magnetic recording medium. For example, in Japanese Unexamined Patent Application Publication No. 2001-255254 and in Japanese Patent No. 4032689, disclosed is a technology of allowing a frequency of light to coincide with a resonant frequency of plasmons that are generated in a metal, by directly applying light to a plasmon generator in order to generate near-field light. In the method of directly applying light to a plasmon generator, however, the plasmon generator itself overheats and accordingly deforms depending on usage environment or conditions, making it difficult to achieve practical realization.
As a technology capable of avoiding such overheating, Japanese Patent No. 4104584 proposes a thermally-assisted head that uses surface plasmon polariton coupling. In this technology, light propagating through a waveguide (guided light) is not directly applied to a plasmon generator, but the guided light is coupled to the plasmon generator through evanescent coupling, and surface plasmon polaritons generated on a surface of the plasmon generator are utilized.
The thermally-assisted magnetic recording head that utilizes the surface plasmon polariton suppresses a rise in temperature of the plasmon generator to some extent. However, it was confirmed that, when Au (gold) is used to configure the plasmon generator for example, there are cases where contraction (agglomeration) resulting from heat occurs especially in a section, near the ABS, where a volume is low and where the heat concentrates.
Such agglomeration is considered to be a phenomenon caused by gold configuring the plasmon generator not being in a stabled state such as a bulk state. That is, since gold formed through a plating method, a sputtering method, or the like is low in density, it is considered that a rise in temperature upon operation of the thermally-assisted magnetic recording head increases the density thereof, and a crystalline structure thereof advances toward a stabilized state. Hence, it is desirable that a heat treatment be performed in advance during manufacturing to stabilize the crystalline structure of a material (such as gold) configuring the plasmon generator.
On the other hand, since the thermally-assisted magnetic recording head is usually provided together with a magnetic reproducing head that includes the MR element, it is desirable that a heat treatment at a temperature that thermally damages operation performance of the MR element be avoided. Therefore, sufficiently stabilizing a crystalline structure of a constituent material of the plasmon generator to sufficiently suppress the agglomeration thereof upon operation is virtually difficult. When such agglomeration occurs, an end section of the plasmon generator is recessed from the ABS and is away from a magnetic recording medium, incurring a decrease in recording performance.
For the foregoing reasons, what is desired is a thermally-assisted magnetic recording head capable of suppressing agglomeration of a plasmon generator upon operation and performing higher-density magnetic recording.
A thermally-assisted magnetic recording head according to an embodiment of the invention includes: a waveguide; a magnetic pole; and a plasmon generator having a first region and a second region, in which the first region has an one end exposed on an air-bearing surface and another end located on an opposite side of the air-bearing surface, and in which the second region is coupled to the another end of the first region and has a volume greater than a volume of the first region. The first region includes a high-density region having a density that is greater than the density of the second region.
A head gimbals assembly, a head arm assembly, and a magnetic disk unit according to embodiments of the invention each include the above-described thermally-assisted magnetic recording head.
In the thermally-assisted magnetic recording head, as well as the head gimbals assembly, the head arm assembly, and the magnetic disk unit each including the same according to the embodiments of the invention, the first region including the one end exposed on the air-bearing surface has the high-density region that is higher in density than the second region coupled thereto at the backward section thereof. Thus, even when a rise in temperature in the first region is occurred upon operation, agglomeration (agglomeration) thereof is suppressed. Hence, it is possible to prevent recession of the one end in the first region from the air-bearing surface. On the other hand, because the volume of the first region is smaller than the volume of the second region, it is possible to efficiently generate stronger near-field light in the vicinity of the one end, in the first region, exposed on the air-bearing surface, without increasing incidence energy. As a result, it is possible to perform higher-density magnetic recording efficiently without degrading recording performance.
In the thermally-assisted magnetic recording head, etc., according to an embodiment of the invention, advantageously, the density of the high-density region may be equal to or greater than about 1.1 times the density of the second region. Also, preferably, the high-density region may be located closer to the one end exposed on the air-bearing surface than the another end in the first region. Further, advantageously, a size of the first region in a direction orthogonal to the air-bearing surface may be equal to or less than about 100 nanometers. One reason is that these make it possible to ensure the suppression of the agglomeration in the first region.
A method of manufacturing a thermally-assisted magnetic recording head according to an embodiment of the invention includes: forming a plasmon generator including a first region and a second region, the second region being coupled to the first region and having a volume greater than a volume of the first region; heating the plasmon generator under a vacuum atmosphere or under an inert gas atmosphere, thereby applying a stress to the first region derived from thermal expansion of the second region; and forming, following the heating, an air-bearing surface through polishing a part, located on an opposite side of the second region, of the first region.
In the method of manufacturing the thermally-assisted magnetic recording head according to the embodiment of the invention, the heating is performed before the formation of the air-bearing surface, to apply the stress to the first region from the second region utilizing the thermal expansion of the second region to thereby increase the density of the first region. Thus, even when a rise in temperature in the first region having the one end exposed on the air-bearing surface is occurred upon operation, the agglomeration thereof is suppressed in the thermally-assisted magnetic recording head manufactured through this manufacturing method. Hence, it is possible to prevent the recession of the one end in the first region from the air-bearing surface. On the other hand, the volume of the first region is smaller than the volume of the second region. Thus, it is possible to increase the density of the first region sufficiently even with the heating at a relatively low temperature, and to efficiently generate stronger near-field light in the vicinity of the one end, in the first region, exposed on the air-bearing surface without increasing incidence energy. As a result, it is possible to perform higher-density magnetic recording efficiently without degrading recording performance.
In the method of manufacturing the thermally-assisted magnetic recording head according to an embodiment of the invention, advantageously, the heating may be performed by generating near-field light from the plasmon generator to thereby increase a temperature of the plasmon generator. One reason is that this makes it possible to perform the heat treatment easier and effectively on a section where a rise in temperature is generated significantly upon operation after completion. Also, advantageously, a size of the first region in a direction orthogonal to the air-bearing surface may be made equal to or less than about 100 nm by the polishing. Further, advantageously, a size of the first region removed by the polishing in the direction orthogonal to the air-bearing surface may be made equal to or less than about 100 nm. Moreover, advantageously, a high-density region having a density equal to or greater than about 1.1 times a density of the second region may be formed in the first region by the heating. One reason is that these thus make it possible to ensure the suppression of the agglomeration in the first region. Also, preferably, the plasmon generator may be heated at a temperature from about 200 degrees centigrade to about 250 degrees centigrade both inclusive. One reason is that setting a heating temperature at about 200 degrees centigrade or higher sufficiently improves the density of the first region, and setting the heating temperature at about 250 degrees centigrade or lower prevents adverse effect on other structures, especially on a reproducing element such as a magnetoresistive element, for example.
Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings.
First, referring to
Next, the magnetic recording reproducing head 10 is described in more detail with reference to
In the following description, dimensions in the X-axis direction, the Y-axis direction, and the Z-axis direction are referred to as a “width”, a “height” or a “length”, and a “thickness”, respectively, and a closer side and a farther side to/from the ABS 11S in the Y-axis direction are referred to as “front” and “back”, respectively. Moreover, forward and backward in the direction of the arrow M are referred to as a “trailing side” and a “leading side”, respectively, and the X-axis direction and the Z-axis direction are referred to as a “cross track direction” and a “down track direction”, respectively.
The magnetic recording reproducing head 10 has a stacked structure including an insulating layer 13, a reproducing head section 14, a recording head section 16, and a protective layer 17 which are stacked in order on the slider 11. Each of the reproducing head section 14 and the recording head section 16 has an end surface exposed on the ABS 11S.
The reproducing head section 14 uses magneto-resistive effect (MR) to perform a read process. The reproducing head section 14 may be configured by stacking, for example, a lower shield layer 21, an MR element 22, and an upper shield layer 23 in this order on the insulating layer 13.
The lower shield layer 21 and the upper shield layer 23 each may be made of a soft magnetic metal material such as NiFe (nickel iron alloy) for example, and are disposed to face each other with the MR element 22 in between in the stacking direction (in the Z-axis direction). This exhibits a function of protection such that an influence of an unnecessary magnetic field does not reach the MR element 22.
One end surface of the MR element 22 is exposed on the ABS 11S, and the other end surfaces thereof are in contact with an insulating layer 24 that fills a space between the lower shield layer 21 and the upper shield layer 23. The insulating layer 24 is made of an insulating material such as Al2O3 (aluminum oxide), AlN (aluminum nitride), SiO2 (silicon dioxide), and DLC (diamond-like carbon).
The MR element 22 functions as a sensor for reading magnetic information written in the magnetic disk 2. Note that in the present embodiment, in a direction (the Y-axis direction) orthogonal to the ABS 11S, a direction toward the ABS 11S from the MR element 22 or a position near the ABS 11S is referred to as a “forward”, and a direction toward a side opposite to the ABS 11S from the MR element 22 or a position away from the ABS 11S is referred to as a “backward”. The MR element 22 may be, for example, a CPP (Current Perpendicular to Plane)-GMR (Giant Magnetoresistive) element whose sense current flows inside thereof in a stacking direction. The lower shield layer 21 and the upper shield layer 23 each function as an electrode to supply the sense current to the MR element 22.
In the reproducing head section 14 having such a structure, a magnetization direction of a free layer (not illustrated) included in the MR element 22 changes in response to a signal magnetic field from the magnetic disk 2. Thus, the magnetization direction of the free layer shows a change relative to a magnetization direction of a pinned layer (not illustrated) also included in the MR element 22. When the sense current flows through the MR element 22, the relative change in the magnetization directions appears as the change in the electric resistance, and thus, the signal magnetic field is detected with use of the change and the magnetic information is accordingly read out.
An insulating layer 25, an intermediate shield layer 26, and an insulating layer 27 are stacked in order on the reproducing head section 14. The intermediate shield layer 26 functions to prevent a magnetic field generated in the recording head section 16 from reaching the MR element 22, and may be made of, for example, a soft magnetic metal material such as NiFe. The insulating layers 25 and 27 each may be formed of the similar material to that of the insulating layer 24, for example.
The recording head section 16 is a perpendicular magnetic recording head that performs a writing process of thermally-assisted magnetic recording scheme. The recording head section 16 may have, for example, a lower yoke layer 28, a leading shield 29 and a connecting layer 30, a cladding layer 31, a waveguide 32, and a cladding layer 33 in order on the insulating layer 27. Note that a configuration may be employed where the leading shield 29 is omitted.
The lower yoke layer 28, the leading shield 29, and the connecting layer 30 are each made of a soft magnetic metal material such as NiFe. The leading shield 29 is located at a most forward part of the upper surface of the lower yoke layer 28, and is so arranged that one end surface thereof is exposed on the ABS 11S. The connecting layer 30 is located at the backward of the leading shield 29 on the upper surface of the lower yoke layer 28.
The cladding layer 31 is so provided as to cover the lower yoke layer 28, the leading shield 29, and the connecting layer 30.
The waveguide 32 provided on the cladding layer 31 extends in a direction (the Y-axis direction) orthogonal to the ABS 11S. For example, one end surface thereof may be exposed on the ABS 11S, and the other end surface thereof may be exposed at the backward thereof. Note that the forward end surface of the waveguide 32 may be located at a position recessed from the ABS 11S without being exposed on the ABS 11S. The waveguide 32 is formed of a dielectric material that allows laser light to pass therethrough. Specifically, the waveguide 32 may be configured of a material containing essentially one or more of, for example, SiC, DLC, TiOx (titanium oxide), TaOx (tantalum oxide), SiNx (silicon nitride), SiOxNy (silicon oxynitride), Si (silicon), zinc selenide (ZnSe), NbOx (niobium oxide), GaP (gallium phosphide), ZnS (zinc sulfide), ZnTe (zinc telluride), CrOx (chromium oxide), FeOx (iron oxide), CuOx (copper oxide), SrTiOx (strontium titanate), BaTiOx (barium titanate), Ge (germanium), and C (diamond). Containing essentially means that the above-described materials are contained as main components and other materials may be contained as subcomponents (for example, impurity) as long as a refractive index higher than those of the cladding layers 31 and 33 is provided. The waveguide 32 allows laser light from a laser diode 60 (described later) to propagate toward the ABS 11S. Incidentally, although the cross-sectional shape parallel to the ABS 11S of the waveguide 32 is a rectangular as illustrated in
The cladding layers 31 and 33 are each formed of a dielectric material having a refractive index, with respect to laser light propagating through the waveguide 32, lower than that of the waveguide 32. The cladding layers 31 and 33 each may be configured of a material containing essentially (substantially) one or more of, for example, SiOx (silicon oxide), Al2O3 (aluminum oxide), AlN (aluminum nitride), BeO (berylium oxide), SiC (silicon carbide), and DLC (diamond-like carbon). Containing essentially means that the above-described materials are contained as main components and the other materials may be contained as subcomponents (for example, impurity) as long as a refractive index lower than that of the waveguide 32 is provided.
The recording head section 16 further includes a plasmon generator 34 provided above the forward end of the waveguide 32 with the cladding layer 33 in between, and a magnetic pole 35 provided above the plasmon generator 34.
The plasmon generator 34 has a first region 341 and a second region 342 located at the backward thereof. The first region 341 includes one end surface 34AS exposed on the ABS 11S. The second region 342 is coupled to the other end, of the first region 341, located on an opposite side of the ABS 11S, and has a volume greater than a volume of the first region 341.
The first region 341 extends backward over a length L1 from the ABS 11S while maintaining uniform area of a cross section (see
The second region 342 may have a circular planar shape, for example, and has a width larger than a width of the first region 341. A thickness of the second region 342 may be the same as the thickness of the first region 341. However, advantageously, the thickness of the second region 342 may be greater than the thickness of the first region 341 at least in part thereof. One reason is to allow it to function as a heatsink that dissipates heat generated upon operation in the plasmon generator 34.
The first region 341 of the plasmon generator 34 and a first layer 351 (described later) of the magnetic pole 35 are separated away from each other, and a gap 34GP is provided therebetween. The gap 34GP may extend backward over a length L2 from the ABS 11S, for example. The gap 34GP may be filled with the cladding layer 33, for example. It is to be noted that while a case is illustrated in
A constituent material of the plasmon generator 34 may be a conductive material containing one or more of a group consisting of, for example, Pd (palladium), Pt (platinum), Rh (rhodium), Ir (iridium), Ru (ruthenium), Au (gold), Ag (silver), Cu (copper), and aluminum (Al). Among these, Au, Ag, and Cu are more preferable, and Au is most preferable, because chemical stability is superior and near-field light NF (described later) is generated more efficiently. Preferably, a constituent material of the first region 341 may be identical to a constituent material of the second region 342. One reason is that this generates the near-field light NF efficiently. This is also for the purpose of preventing complication during manufacturing.
The magnetic pole 35 has a structure in which the first layer 351 and a second layer 352 are stacked in order on the plasmon generator 34. The first layer 351 has an end surface 35S1 exposed on the air bearing surface 11S, and a counter surface 35S2 facing the plasmon generator 34. The second layer 352 extends backward from a position recessed from the ABS 11S by a length L2 (>L1).
Each of the first layer 351 and the second layer 352 may be made of a magnetic material having high saturation flux density such as iron-based alloy, for example. Examples of the iron-based alloy may include FeCo (iron cobalt alloy), FeNi (iron nickel alloy), and FeCoNi (iron cobalt nickel alloy). Incidentally, although a cross-sectional shape of the first layer 351 parallel to the ABS 11S is an inverted trapezoid as illustrated in
The plasmon generator 34 generates the near-field light NF from the ABS 11S, based on the laser light which has propagated through the waveguide 32. The magnetic pole 35 stores therein magnetic flux generated in a coil 41 (described later), and releases the magnetic flux from the ABS 11S to thereby generate a recording magnetic field for recording magnetic information into the magnetic disk 2. The plasmon generator 34 and the first layer 351 are embedded in the cladding layer 33.
The recording head section 16 further includes a connecting layer 36 embedded in the cladding layer 33 at the backward of the plasmon generator 34 and the magnetic pole 35, and a connecting layer 37 so provided as to be in contact with an upper surface of the connecting layer 36, as illustrated in
As illustrated in
In the recording head section 16 having the foregoing structure, the write current flowing through the coil 41 generates a magnetic flux inside a magnetic path that is mainly configured by the leading shield 29, the lower yoke layer 28, the connecting layers 30, 36, and 37, the upper yoke layer 43, and the magnetic pole 35. This generates a signal magnetic field near the end surface of the magnetic pole 35 exposed on the ABS 115, and the signal magnetic field reaches a predetermined region of the recording surface of the magnetic disk 2.
Further, in the magnetic recording reproducing head 10, the protective layer 17 which may be formed of a material similar to that of the cladding layer 33 for example is so formed as to cover the entire upper surface of the recording head section 16. In other words, the cladding layer 33 and the protective layer 17 that are each formed of a material having a lower refractive index compared with the waveguide 32 and high thermal conductivity are so provided as to collectively surround the waveguide 32, the plasmon generator 34, and the magnetic pole 35.
[3. Method of Manufacturing Magnetic Recording Reproducing Head]
A method of manufacturing the magnetic recording reproducing head 10 will be described with reference to
First, as illustrated in
The magnetic recording reproducing head 10 is manufactured mainly by subsequently forming and stacking a series of components by using an existing thin-film process. Examples of the existing thin-film process may include film-forming technique such as electrolytic plating and sputtering, patterning technique such as photolithography, etching technique such as dry etching and wet etching, and polishing technique such as chemical mechanical polishing (CMP).
Here, first, the insulating layer 13 is formed on the slider 11. Then, the lower shield layer 21, the MR element 22 and the insulating layer 24, and the upper shield layer 23 are formed by stacking in this order on the insulating layer 13 to form the reproducing head section 14. Then, the insulating layer 25, the intermediate shield layer 26, and the insulating layer 27 are stacked in order on the reproducing head section 14.
Thereafter, the lower yoke layer 28, the leading shield 29 and the connecting layer 30, the cladding layer 31, the waveguide 32, the cladding layer 33, the plasmon generator 34, the magnetic pole 35, and the connecting layers 36 and 37 are formed in order on the insulating layer 27. Note that a configuration may be employed where the leading shield 29 is omitted. Further, the insulating layer 38 is so formed as to cover an entire part, following which a planarization process is performed to planarize the upper surfaces of the magnetic pole 35, the insulating layer 38, and the connecting layer 37, followed by forming the coil 41 embedded by the insulating layers 39 and 42. Moreover, the upper yoke layer 43 connected with the magnetic pole 35 and the connecting layer 37 is formed to complete the recording head section 16. Thereafter, the protective layer 17 is formed on the recording head section 16. As a result, the plurality of magnetic recording reproducing heads 10 before the formation of the ABS 11S are formed in an array on the wafer 11ZZ (
Thereafter, as illustrated in
After forming the plurality of bars 11Z, these bars 11Z are heated. Specifically, the bars 11Z are heated under a vacuum atmosphere or an inert gas atmosphere to perform heating on the plasmon generator 34 (the first region 341). This causes thermal expansion of the second region 342, thereby applying a stress from the second region 342 to the first region 341 under a high temperature and thus increasing the density of the first region 341. In performing the heating, laser light may be caused to enter the waveguide 32 and the near-field light NF may be generated from the tip section 34G of the first region 341 to increase a temperature of the first region 341. In this heat treatment, preferably, the heating may be so performed as to allow a temperature of the first region 341 to be from about 200 degrees centigrade to about 250 degrees centigrade both inclusive. One reason is that setting the heating temperature at about 200 degrees centigrade or higher sufficiently improves the density of the first region 341, and setting the heating temperature at about 250 degrees centigrade or lower prevents adverse effect on other structures, especially on the MR element 22.
Further, one end surface of the bar 11Z, i.e., a side surface of the stacked structure from the slider 11 up to the protective layer 17, is collectively polished through the CMP method or the like, etc., to form the ABS 11S (
[4. Detailed Structure of Light Source Unit]
Referring again to
The light source unit 50 provided at the backward of the magnetic recording reproducing head 10 includes the laser diode 60 as a light source emitting laser light, and a supporting member 51, which may be rectangular-solid in shape for example, supporting the laser diode 60 as illustrated in
The supporting member 51 may be formed of, for example, a ceramic material such as Al2O3.TiC. As illustrated in
Those that are generally used for communication, for optical disc storage, or for material analysis, such as InP-based, GaAs-based, and GaN-based ones, can be applied to the laser diode 60. A wavelength of the laser light emitted from the laser diode 60 may have any value within a range of from 375 nm to 1.7 μm, for example. Specifically, an example includes a laser diode of InGaAsP/InP quaternary mixed crystal having the emission wavelength region of from 1.2 to 1.67 gm. As illustrated in
[5. Control Circuit of Magnetic Disk Unit and Operation]
Next, a circuit configuration of a control circuit of the magnetic disk unit illustrated in
Here, the control LSI 100 provides write data and a write control signal to the write gate 111. Moreover, the control LSI 100 provides a read control signal to the constant current circuit 121 and the demodulation circuit 123, and receives read data output from the demodulation circuit 123. In addition, the control LSI 100 provides a laser ON/OFF signal and an operation current control signal to the laser control circuit 131.
The temperature detector 132 detects a temperature of a magnetic recording layer of the magnetic disk 2 to transmit information on the temperature to the control LSI 100.
The ROM 101 stores therein a control table and the like in order to control an operation current value to be supplied to the laser diode 60.
At the time of write operation, the control LSI 100 supplies the write data to the write gate 111. The write gate 111 supplies the write data to the write circuit 112 only when the write control signal instructs to perform the write operation. The write circuit 112 allows the write current to flow through the coil 41 according to the write data. As a result, a recording magnetic field is generated from the magnetic pole 35, and data is written into the magnetic recording layer of the magnetic disk 2 by the recording magnetic field.
At the time of read operation, the constant current circuit 121 supplies a constant sense current to the MR element 22 only when the read control signal instructs to perform the read operation. An output voltage of the MR element 22 is amplified by the amplifier 122, which is then received by the demodulation circuit 123. The demodulation circuit 123 demodulates the output of the amplifier 122 to generate read data to be provided to the control LSI 100 when the read control signal instructs to perform the read operation.
The laser control circuit 131 controls the supply of operation current to the laser diode 60 based on the laser ON/OFF signal, and controls the value of the operation current supplied to the laser diode 60 based on the operation current control signal. The operation current equal to or larger than an oscillation threshold is supplied to the laser diode 60 by the control of the laser control circuit 131 when the laser ON/OFF signal instructs to perform the ON operation. As a result, the laser light is emitted from the laser diode 60 and the laser light propagates through a core 32. Subsequently, the near-field light NF (described later) is generated from the tip section 34G of the plasmon generator 34. By the near-field light NF, a part of the magnetic recording layer of the magnetic disk 2 is heated, and thus the coercivity in that part is lowered. At the time of writing, the recording magnetic field generated from the magnetic pole 35 is applied to the part of the magnetic recording layer where the coercivity is lowered, and thus data recording is performed.
The control LSI 100 determines a value of the operation current of the laser diode 60 with reference to the control table stored in the ROM 101, based on a temperature of the magnetic recording layer of the magnetic disk 2 measured by the temperature detector 132, etc., and controls the laser control circuit 131 with use of the operation current control signal such that the operation current with that value is supplied to the laser diode 60. For example, the control table may include an oscillation threshold of the laser diode 60 and data indicating a temperature dependency of light output-operation current property. The control table may further include data indicating a relationship between the operation current value and an increased amount of the temperature of the magnetic recording layer heated by the near-field light NF, data indicating a temperature dependency of the coercivity of the magnetic recording layer, and the like.
The control circuit illustrated in
Next, a principle of near-field light generation and a principle of thermally-assisted magnetic recording with use of the near-field light according to the present embodiment will be described with reference to
Laser light 45 emitted from the laser diode 60 propagates through the waveguide 32 to reach the neighborhood of the plasmon generator 34. At this time, the laser light 45 is totally reflected by an evanescent light generating surface 32C that is an interface between the waveguide 32 and a buffer section 33A (a section between the waveguide 32 and the plasmon generator 34, of the cladding layer 33), thereby generating evanescent light 46 that leaks into the buffer section 33A. Thereafter, the evanescent light 46 couples with charge fluctuation, on a surface plasmon exciting surface 34S 1 that faces the waveguide 32 of the plasmon generator 34, to induce a surface plasmon polariton mode. As a result, surface plasmons 47 are excited on the surface plasmon exciting surface 34S 1. The surface plasmons 47 propagate on the surface plasmon exciting surface 34S1 toward the ABS 11S.
The surface plasmons 47 eventually reach the ABS 11S, and as a result, the near-field light NF is generated on the tip section 34G. The near-field light NF is radiated toward the magnetic disk 2 (not illustrated in
[6. Effects]
According to the magnetic recording reproducing head 10 of the present embodiment, the first region 341 including the one end surface exposed on the ABS 11S has the high-density region 34HD that is higher in density than the second region 342 coupled thereto at the backward section thereof, as described above. Thus, the agglomeration of the first region 341 is suppressed even when a rise in temperature in the first region 341 is occurred upon operation. Hence, it is possible to prevent recession of the one end surface 34AS from the ABS 11S. On the other hand, because the volume of the first region 341 is smaller than the volume of the second region 342, it is possible to efficiently generate the stronger near-field light NF in the vicinity of the one end surface 34AS without increasing incidence energy on the waveguide 32. As a result, it is possible to perform higher-density magnetic recording efficiently without degrading recording performance.
Also, in the method of manufacturing the magnetic recording reproducing head 10 according to the present embodiment, the heat treatment is performed before the formation of the ABS 11S, to apply a stress to the first region 341 derived from the thermal expansion of the second region 342 under a high temperature to thereby increase the density of the first region 341. Thus, in the magnetic recording reproducing head 10 manufactured through this manufacturing method, the agglomeration of the first region 341 is suppressed even when a rise in temperature in the first region 341 including the one end surface 34AS exposed on the ABS 11S is occurred upon operation thereof. Hence, it is possible to prevent recession of the one end surface 34AS from the ABS 11S. On the other hand, the volume of the first region 341 is made smaller than the volume of the second region 342. Thus, it is possible to increase the density of the first region 341 sufficiently even with the heat treatment at a relatively low temperature, and to efficiently generate the stronger near-field light NF in the vicinity of the one end surface 34AS without increasing incidence energy on the waveguide 32. As a result, it is possible to perform higher-density magnetic recording efficiently without degrading recording performance.
Further, allowing the configuration to satisfy at least one of the following requirements in the present embodiment makes it possible to ensure the suppression of the agglomeration in the first region 341. Specifically, first, the density of the high-density region 34HD may be made equal to or greater than 1.1 times the density of the second region 342, second, the high-density region may be located, in the first region 341, closer to the one end surface 34AS than the other end coupled to the second region 342, and third, the length L1 of the first region 341 in the direction orthogonal to the ABS 11S may be made equal to or less than about 100 nm.
Examples of the invention will be described in detail.
A test on lifetime was conducted, at the following conditions, on the magnetic recording reproducing head 10 of the invention, obtained through subjecting the plasmon generator 34 in which the length L1 and the length L4 were both 100 nm to a heat treatment and polishing the same, as illustrated in
A test on lifetime was conducted, at conditions similar to those described above, on the magnetic recording reproducing head 10 of the invention, obtained through subjecting the plasmon generator 34 in which the length L1 was 100 nm and the length L4 was 300 nm to the heat treatment and polishing the same, as illustrated in
As a Comparative Example, a similar lifetime test was performed also on a magnetic recording reproducing head, which was obtained in a similar way to the Experiment 1 except that a plasmon generator 134, in which a third region 342 was provided on an opposite side of the second region 342 with the first region 341 interposed in between, was fabricated, as illustrated in
An analysis on density performed on each of the samples utilizing an electron diffraction method confirmed that a density near an end section in the first region 341 was equal to or greater than 1.1 times a density of other region in the Experiment 1. In the Experiment 2, it was confirmed that the density near the end section in the first region 341 was greater than the density of other region by about few percent. In contrast, in the Experiment 3, a difference between the density of the first region 341 and the density of the second region 342 was hardly confirmed. Therefore, the higher density of the first region 341 as compared with the density of the second region 342 in the plasmon generator 34 presumably provides the longer lifetime of the magnetic recording reproducing head 10.
Incidentally, the density analysis utilizing the electron diffraction method includes a Convergent-Beam Electron Diffraction (CBED) method, an Electron Energy-Loss Spectroscopy (EELS) method, or the like. The convergent-beam electron diffraction method, the electron energy-loss spectroscopy method, or the like makes it possible to measure a density of a micro region when a sample thickness of an observation area is precisely defined.
Next, a relationship between the length L4 and lifetime was examined. Here, a lifetime test was performed on those that were fabricated in a similar way to those according to the Experiment 1 except that the length L4 of the region removed by the polishing process was varied, and was performed at conditions similar thereto. Table 1 shows a result thereof, where each of the Experiments 4-1 to 4-5 represents a mean value of six samples in the Table 1.
As shown in the Table 1, it was found that allowing the length L4, i.e., the length of the region removed by the polishing process, to be 10 nm or less makes it possible to achieve longer lifetime. One reason is that the density in the end section of the first region 341 following the polishing process depends on the length L4. Incidentally, it was also confirmed that allowing the length L1 to be short increases slightly the density in the end section of the first region 341 following the polishing process. However, it was also found that the density thereof is controlled stronger by the length L4 than by the length L1.
While the invention has been described with reference to an embodiment, the invention is not limited to the foregoing embodiment and various modifications may be made. For example, the thermally-assisted magnetic recording head of the invention is not limited to that described in the foregoing embodiment in configurations (such as shapes and positional relationships) of the waveguide, the plasmon generator, the magnetic pole, etc., and the thermally-assisted magnetic recording head may have any other configuration.
Correspondence relationships between the reference numerals and the components in the present embodiment are collectively illustrated as follows. 1 . . . housing, 2 . . . magnetic disc, 3 . . . head arm assembly (HAA), 4 . . . head gimbals assembly (HGA), 4A . . . magnetic head device, 4B . . . suspension, 5 . . . arm, 6 . . . driver, 7 . . . fixed shaft, 8 . . . bearing, 9 . . . spindle motor, 10 . . . magnetic recording reproducing head, 11 . . . slider, 11A . . . element forming surface, 11B . . . back surface, 11S . . . air bearing surface (ABS), 12 . . . element forming layer, 13 . . . insulating layer, 14 . . . reproducing head section, 16 . . . recording head section, 17 . . . protective layer, 21 . . . lower shield layer, 22 . . . MR element, 23 . . . upper shield layer, 24, 25, 27, 38, 39, 42 . . . insulating layer, 26 . . . intermediate shield layer, 28 . . . lower yoke layer, 29 . . . leading shield, 30, 36, 37 . . . connecting layer, 31, 33 . . . cladding layer, 32 . . . waveguide, 34 . . . plasmon generator, 34HD . . . high-density region, 341 . . . first region, 342 . . . second region, 34G . . . tip section, 34S1 . . . surface plasmon exciting surface, 35 . . . magnetic pole, 351 . . . first layer, 352 . . . second layer, 41 . . . coil, 43 . . . upper yoke layer, 45 . . . laser light, 46 . . . evanescent light, 47 . . . surface plasmon, 100 . . . LSI, 101 . . . ROM, 111 . . . write gate, 121 . . . constant current circuit, 122 . . . amplifier, 123 . . . demodulation circuit, 131 . . . laser control circuit, 132 . . . temperature detector, NF . . . near-field light.
