Disc device

Abstract

To provide a disc device capable of reducing deterioration of an assist element attributable to heat generation at an element part.SOLUTION: According to an embodiment, a disc device includes: a recording medium that is disc-shaped and rotatable; a magnetic head, and a controller. The magnetic head includes: a recording head having a main pole, a light shield pole, and a coil; an assist element; and a heater that heats the recording head. The controller includes: a heater voltage supply circuit; a driving voltage supply circuit that supplies the assist element with a driving voltage; and a contact detection circuit, and adjusts a set value of the driving voltage based on an amount of projection of the assist element upon detection of contact by the contact detection circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a disk device. [Background technology]

[0002] In recent years, magnetic disk drives using magnetic heads for perpendicular magnetic recording have been proposed as disk drives to achieve higher recording density, larger capacity, and smaller size. In such magnetic heads, the recording head includes a main pole that generates a perpendicular magnetic field, a write shield pole positioned on the trailing side of the main pole across a write gap, and a coil for passing magnetic flux through the main pole. Furthermore, to improve recording density, recording heads equipped with assist elements such as high-frequency assist elements, write assist elements, and thermal assist elements have been proposed. In disk drives equipped with such recording heads, the drive voltage applied to the assist elements is set to a desired value in terms of voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-107379 [Patent Document 2] U.S. Patent No. 10,014,009 [Patent Document 3] U.S. Patent No. 11,341,991 [Patent Document 4] U.S. Patent No. 10,622,010 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even when the drive voltage is set to a desired value, variations in the self-heating of the element unit may occur due to variations in the dimensions of the assist element, variations in the shape around the element, etc. If the amount of heat generated by the assist element is large, the assist element and the parts of the recording head near the element unit may oxidize, causing a degradation phenomenon in which the recording performance of the recording head deteriorates. An object of the embodiments of the present invention is to provide a disk device capable of reducing the deterioration of the assist element caused by heat generation in the element portion. [Means for solving the problem]

[0005] According to an embodiment, the disk device includes: a rotatable disk-shaped recording medium having a magnetic recording layer; a magnetic head including a write head having a main pole that generates a recording magnetic field, a write shield pole that faces the main pole across a write gap, and a coil that excites magnetic flux; an assist element; and a heater that heats the write head; a controller including a heater voltage supply circuit that supplies a heater voltage to the heater, a drive voltage supply circuit that supplies a drive voltage to the assist element, and a contact detection circuit that detects contact between the magnetic head and the recording medium, and that adjusts a set value of the drive voltage based on the protrusion amount of the assist element when contact is detected by the contact detection circuit; It is equipped with: [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram schematically showing a hard disk drive (HDD) according to a first embodiment. [Figure 2] FIG. 2 is a side view schematically showing the magnetic head, suspension, and magnetic disk in the HDD. [Figure 3] FIG. 3 is an enlarged cross-sectional view of a head portion of the magnetic head. [Figure 4] FIG. 4 is a perspective view schematically showing a recording head of the magnetic head. [Figure 5]FIG. 5 is an enlarged cross-sectional view showing the tip of the recording head. [Figure 6] FIG. 6 is a plan view of the recording head of the magnetic head as viewed from the ABS side. [Figure 7] FIG. 7 is a diagram showing the relationship between the environmental temperature and the life of the assist element. [Figure 8] FIG. 8 is a diagram showing the relationship between the protrusion amount of the assist element and the temperature rise of the element portion. [Figure 9] FIG. 9 is a flowchart illustrating a flow for setting the drive voltage of the assist element in the HDD. [Figure 10] FIG. 10 is a flowchart showing a flow for setting the flying height of the magnetic head in the HDD. [Figure 11] FIG. 11 is a diagram showing a schematic comparison of the element life of the assist element between the HDD according to the present embodiment and an HDD according to a comparative example. [Figure 12] FIG. 12 is a diagram showing the relationship between the temperature inside the device and the target value of the protrusion amount of the element in the hard disk drive (HDD) according to the second embodiment. [Figure 13] FIG. 13 is a cross-sectional view of a print head, illustrating a relationship between the protrusion amount of the print head and the protrusion amount of the assist element in an HDD according to a second embodiment. [Figure 14] FIG. 14 is a plan view schematically showing different radial positions of a magnetic head relative to a magnetic disk in an HDD according to a third embodiment. [Figure 15] FIG. 15 is a plan view schematically showing the skew state of the magnetic head at different radial positions. [Figure 16] FIG. 16 is a diagram showing the relationship between the initial flying height of the magnetic head, the protrusion amount of the element portion, and the target value in the HDD according to the third embodiment. [Figure 17] FIG. 17 is a diagram showing the relationship between the radial position of the magnetic head and the initial flying height of the magnetic head in the HDD according to the third embodiment. [Figure 18] FIG. 18 is a plan view of the recording head of the magnetic head according to the first modification, viewed from the ABS side. [Figure 19]FIG. 19 is an enlarged cross-sectional view showing a head portion of a magnetic head according to a second modification. DETAILED DESCRIPTION OF THE INVENTION

[0007] A disk device according to an embodiment will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that are easily conceivable by those skilled in the art while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be omitted or simplified as appropriate.

[0008] (First embodiment) As a disk device, a hard disk drive (HDD) according to the first embodiment will be described in detail. Fig. 1 is a block diagram showing a schematic diagram of the HDD according to the first embodiment, and Fig. 2 is a side view showing a magnetic head and a magnetic disk in a floating state. As shown in FIG. 1, a HDD 10 includes a rectangular housing 11, a magnetic disk 12 as a recording medium disposed within the housing 11, a spindle motor 14 that supports and rotates the magnetic disk 12, and multiple magnetic heads 16 (only one is shown) that write and read data to and from the magnetic disk 12. The HDD 10 also includes a head actuator 18 that moves and positions the magnetic head 16 over any track on the magnetic disk 12. The head actuator 18 includes a carriage assembly 20 that movably supports the magnetic head 16 and a voice coil motor (VCM) 22 that rotates the carriage assembly 20. The carriage assembly 20 includes an arm that is rotatably supported around a bearing 24 and a suspension 26 that extends from the arm. The magnetic head 16 is supported at the tip of the suspension 26.

[0009] The controller of the HDD 10 includes a head amplifier IC 30 that drives the magnetic head 16, a main controller 40, a driver IC 48, and a temperature sensor S1 that detects the ambient temperature. The head amplifier IC 30 is provided, for example, in the carriage assembly 20 and is electrically connected to the magnetic head 16. The head amplifier IC 30 includes a recording current supply circuit (recording current supply unit) 81 that supplies a recording current to the recording coil of the magnetic head 16, an assist element drive voltage supply circuit (hereinafter referred to as a drive voltage supply circuit) 82 that supplies a drive voltage (e.g., a bias voltage) to an assist element (described later), a heater voltage supply circuit 83 that supplies a drive voltage to a heater (described later), a read voltage supply circuit 84 that amplifies a signal read by the magnetic head, and a contact detection circuit 85 that detects contact between the magnetic head 16 and the magnetic disk.

[0010] The main controller 40, driver IC 48, and temperature sensor S1 are configured, for example, on a control circuit board (not shown) provided on the rear side of the housing 11. The main controller 40 includes an R / W channel 42, a hard disk controller (HDC) 44, a microprocessor (MPU) 46, and a memory 43. The main controller 40 is electrically connected to the magnetic head 16 via a head amplifier IC 30. The main controller 40 is electrically connected to the VCM 22 and spindle motor 14 via a driver IC 48. The HDC 44 can be connected to a host computer (not shown). The memory 43 of the main controller 40 stores various setting data, such as initial setting values ​​for the heater of the magnetic head and the initial flying height of the magnetic head, which will be described later.

[0011] As shown in FIGS. 1 and 2, the magnetic disk 12 is configured as a perpendicular magnetic recording medium. The magnetic disk 12 has a substrate 101 made of a non-magnetic material. The substrate 101 is formed, for example, in the shape of a disk with a diameter of 95 mm (3.5 inches). On each surface of the substrate 101, a soft magnetic layer 102 made of a material exhibiting soft magnetic properties is formed, and on the upper layer thereof, a perpendicular magnetic recording layer 103 having magnetic anisotropy in a direction perpendicular to the surface of the magnetic disk 12 and a protective film 104 are sequentially laminated. The multiple magnetic disks 12 are coaxially fitted to the hub of a spindle motor 14. The magnetic disks 12 are rotated by the spindle motor 14 at a predetermined speed in the direction of arrow B.

[0012] 2, the magnetic head 16 is supported on the extending ends of the suspensions 26. The magnetic head 16 is electrically connected to a head amplifier IC 30 via a wiring member (flexure) 28 provided on the carriage assembly 20. The magnetic head 16 is configured as a floating-type head and includes a slider 15 formed in a substantially rectangular parallelepiped shape and a head portion 17 formed at the end of the slider 15 on the trailing end 15b side. The slider 15 is formed, for example, from a sintered body (AlTiC) of alumina and titanium carbide. The head portion 17 is formed from multiple thin films. The slider 15 is attached to a gimbal portion 27 of a wiring member 28.

[0013] The slider 15 has a rectangular disk-facing surface (air bearing surface (ABS)) 13 that faces the surface of the magnetic disk 12. The slider 15 is maintained in a state where it is lifted a predetermined distance above the surface of the magnetic disk 12 by an air flow C that is generated between the disk surface and the ABS 13 as the magnetic disk 12 rotates. The direction of the air flow C coincides with the rotation direction B of the magnetic disk 12. The slider 15 has a leading end 15a located on the inflow side of the air flow C and a trailing end 15b located on the outflow side of the air flow C. As the magnetic disk 12 rotates, the magnetic head 16 moves in the direction opposite to the direction of arrow B relative to the magnetic disk 12.

[0014] 3 is an enlarged cross-sectional view of the head portion 17 of the magnetic head 16 and the magnetic disk 12. As shown in the figure, the head portion 17 has a reproducing head (read head) 54 and a recording head (writer) 58 formed by a thin-film process on the trailing end 15b of the slider 15, and is formed as a separate magnetic head. The read head 54 and the recording head 58 are covered with a non-magnetic protective insulating film 53, except for the portions exposed to the ABS 13 of the slider 15. The protective insulating film 53 forms the outer shape of the head portion 17.

[0015] The longitudinal direction of a recording track formed on the magnetic recording layer 103 of the magnetic disk 12 is defined as the down-track direction DT, and the width direction of the recording track is defined as the cross-track direction WT. The read head 54 has a magnetoresistive element 55 and a first magnetic shield film 56 and a second magnetic shield film 57 arranged on the leading side (inflow side) and trailing side (outflow side) of the magnetoresistive element 55 in the downtrack direction DT, respectively, to sandwich the magnetoresistive element 55. The magnetoresistive element 55 and the first and second magnetic shield films 56, 57 extend approximately perpendicular to the ABS 13. The lower ends of the magnetoresistive element 55 and the first and second magnetic shield films 56, 57 are exposed to the ABS 13.

[0016] The recording head 58 is provided on the trailing end 15b side of the slider 15 relative to the read head 54. Fig. 4 is a perspective view of the recording head cut at the track center, Fig. 5 is an enlarged cross-sectional view of the tip (end on the ABS side) of the recording head, and Fig. 6 is a plan view of the recording head viewed from the ABS side. As shown in FIGS. 3 and 4 , the recording head 58 includes a main pole 60 that generates a recording magnetic field perpendicular to the surface of the magnetic disk 12, a trailing shield (write shield pole) 62 that is located on the trailing side of the main pole 60 and faces the main pole 60 across a write gap WG, a leading shield 64 that faces the leading side of the main pole 60, a pair of side shields 63 that are located on both sides of the main pole 60 in the cross-track direction CT, and an assist element that is located between the main pole 60 and the trailing shield 62 within the write gap WG. In this embodiment, a high-frequency oscillator, such as a spin torque oscillator (STO) 65, is used as the assist element. The main pole 60 and the trailing shield 62 form a first magnetic core that forms a magnetic path, and the main pole 60 and the leading shield 64 form a second magnetic core that also forms a magnetic path. The recording head 58 includes a first recording coil 70 wound around the first magnetic core and a second recording coil 72 wound around the second magnetic core.

[0017] The main pole 60 is made of a soft magnetic material with high magnetic permeability and high saturation magnetic flux density, and extends substantially perpendicular to the ABS 13. A tip 60a of the main pole 60 on the ABS 13 side tapers toward the ABS 13 and is formed into a columnar shape that is narrower than the other portions. The tip surface of the main pole 60 is exposed to the ABS 13 of the slider 15. As shown in FIGS. 5 and 6 , the tip 60a of the main pole 60 has a flat trailing end face 60b that faces the trailing shield 62 with a gap therebetween. The tip 60a has, for example, a trapezoidal cross section. The trapezoidal tip (tip face) 60a has a trailing end face 60b extending in the cross-track direction CT, a leading end face 60c facing the trailing end face 60b, and both side faces 60d. At the ABS 13, the width of the tip 60a, i.e., the width WP of the trailing end face 60b in the cross-track direction CT, approximately corresponds to the track width of the recording track on the magnetic disk 12. At the tip 60a, the trailing end face 60b and the leading end face 60c may extend in a direction perpendicular to the ABS 13 or may extend at an angle relative to the direction perpendicular to the ABS 13. Both side surfaces 60d extend at an angle with respect to the central axis C of the main pole 60, i.e., with respect to the down-track direction DT.

[0018] As shown in FIGS. 3 to 6 , the trailing shield 62 is made of a soft magnetic material and is provided to efficiently close a magnetic path through the soft magnetic layer 102 of the magnetic disk 12 directly below the main pole 60. The trailing shield 62 is disposed on the trailing side of the main pole 60. The trailing shield 62 is formed in a substantially L-shape, and its tip 62a is formed in an elongated rectangular shape. The tip surface of the trailing shield 62 is exposed to the ABS 13 of the slider 15. The tip 62a has a leading end surface (pole tip surface) 62b that faces the tip 60a of the main pole 60. The leading end surface 62b is sufficiently longer than the width WP of the tip 60a of the main pole 60 and the track width of the magnetic disk 12 and extends along the cross-track direction CT. The leading end surface 62b extends perpendicular to or slightly inclined from the ABS 13. In the ABS 13, the lower edge of the leading end face 62b faces the trailing end face 60b of the main pole 60 in parallel with a write gap WG (gap length in the down-track direction DT) therebetween.

[0019] 4 and 5 , the trailing shield 62 has a first connection portion 50 connected to the main pole 60. The first connection portion 50 is magnetically connected to the top of the main pole 60, i.e., a portion of the main pole 60 away from the ABS 13, via a non-conductor 52. The first write coil 70 is wound around the first connection portion 50 in the first magnetic core, for example. When writing a signal to the magnetic disk 12, a write current is passed through the first write coil 70, which excites the main pole 60 and causes magnetic flux to flow through the main pole 60.

[0020] 4 and 6, the pair of side shields 63 are arranged on both sides of the main pole 60 in the cross-track direction CT so as to be physically separated from the main pole 60 and connected to the trailing shield 62. In this embodiment, the side shields 63 are made of a high-permeability material and are formed integrally with the tip portion 62a of the trailing shield 62, and extend from the leading-side end face 62b of the tip portion 62a toward the leading end of the slider 15.

[0021] As shown in FIGS. 3 to 5 , the leading shield 64 made of a soft magnetic material is provided on the leading side of the main pole 60, facing the main pole 60. The leading shield 64 is formed in a substantially L-shape, and a tip portion 64a on the ABS 13 side is formed in an elongated rectangular shape. The tip surface (lower end surface) of the tip portion 64a is exposed to the ABS 13. A trailing-side end surface 64b of the tip portion 64a extends along the cross-track direction CT. At the ABS 13, the trailing-side end surface 64b faces the leading-side end surface 60c of the main pole 60 with a gap between them. In this embodiment, the tip portion 64a of the leading shield 64 is formed integrally with the side shield 74 using a high-permeability material.

[0022] The leading shield 64 also has a second connection portion 68 joined to the main pole 60 at a position away from the ABS 13. The second connection portion 68 is formed of, for example, a soft magnetic material and is magnetically connected to the top of the main pole 60, i.e., the portion of the main pole 60 away from the ABS 13, via a non-conductor 59. This allows the second connection portion 68 to form a magnetic circuit together with the main pole 60 and the leading shield 64. The second write coil 72 of the write head 58 is arranged, for example, wound around the second connection portion 68, and applies a magnetic field to this magnetic circuit.

[0023] As shown in FIGS. 5 and 6 , the STO 65, which functions as a high-frequency oscillator, is provided in the write gap WG between the tip 60a of the main pole 60 and the tip 62a of the trailing shield 62. The STO 65 is primarily made of an alloy material such as Fe, Co, or Ni. The STO 65 includes a spin injection layer 65a, an intermediate layer (nonmagnetic conductive layer) 65b, and an oscillation layer 65c, which are stacked in order from the main pole 60 side to the trailing shield 62 side, i.e., along the downtrack direction DT of the magnetic head 16. The spin injection layer 65a is bonded to the trailing end surface 60b of the main pole 60 via a nonmagnetic conductive layer (underlayer) 67a. The oscillation layer 65c is bonded to the leading end surface 62b of the trailing shield 62 via a nonmagnetic conductive layer (cap layer) 67b. The stacking order of the spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c may be reversed, that is, they may be stacked in order from the trailing shield 62 side to the main pole 60 side.

[0024] At least the bottom surface of the oscillation layer 65c, and in this embodiment, the entire bottom surface of the STO 65 including the spin injection layer 65a, intermediate layer 65b, and oscillation layer 65c, is exposed to the ABS 13 and extends flush with the ABS 13. Alternatively, the entire bottom surface of the STO 65 may be positioned in a direction away from the ABS 13, for example, in a direction perpendicular to the ABS 13, and receding toward the rear, i.e., spaced apart. The bottom surface of the STO 65 is not limited to a flat shape, but may also be formed in an arc shape that is convex upward. The height in the direction perpendicular to the ABS 13 is defined as the element height SH.

[0025] 6, at the ABS 13, the width WS of the STO 65 in the cross-track direction CT is larger than the width WP of the trailing-side end face 60b of the main pole 60 (WS>WP). In one example, the width WS of the STO 65 is approximately 1.1 to 1.6 times the width WP of the main pole 60. In this embodiment, the STO 65 is disposed symmetrically with respect to the central axis C of the write head, and covers both end edges of the trailing-side end face 60b in the cross-track direction CT. In other words, both end portions of the STO 65 in the cross-track direction CT extend beyond the end edges of the trailing-side end face 60b to the outside of the main pole 60. The width WS of the STO 65 is not limited to being larger than the width WP of the main pole 60, but may be equal to or smaller than the width WP (WS≦WP).

[0026] 4 and 5, the main pole 60 and the trailing shield 62 are each connected to the connection terminal 45 via wiring, and are further connected to the head amplifier IC 30 and the main controller 40 via the flexure 28. A current circuit is configured to pass the STO drive current (bias voltage) in series from the head amplifier IC 30 through the main pole 60, STO 65, and trailing shield 62.

[0027] The first and second recording coils 70 and 72 are each connected to a connection terminal 45 via wiring and further connected to a head amplifier IC via a flexure 28. The second recording coil 72 is wound in the opposite direction to the first recording coil 70. When writing a signal to the magnetic disk 12, a recording current is supplied from a recording current supply circuit 81 of the head amplifier IC 30 to the first and second recording coils 70 and 72, thereby exciting the main pole 60 and causing magnetic flux to flow through the main pole 60. The recording current supplied to the first and second recording coils 70 and 72 is controlled by the main controller 40. The second recording coil 72 may be connected in series with the first recording coil 70. Alternatively, the current supply to the first and second recording coils 70 and 72 may be controlled separately.

[0028] 3, the magnetic head 16 further includes a first heater (write heater) 76a and a second heater (read heater) 76b as heating means for adjusting the flying height of the magnetic head. The first heater 76a is provided near the recording head 58, for example, between the first recording coil 70 and the second recording coil 72, and near the main pole 60. The second heater 76b is provided near the read head 54. The first heater 76a and the second heater 76b are each connected to the connection terminal 45 via wiring, and further connected to the head amplifier IC 30 via the flexure 28.

[0029] During operation of the HDD 10 configured as described above, the main controller 40, under the control of the MPU 46, drives the spindle motor 14 via the driver IC 48 to rotate the magnetic disk 12 at a predetermined speed. The main controller 40 also drives the VCM 22 via the driver IC 48 to move and position the magnetic head 16 over a desired track on the magnetic disk 12. The ABS 13 of the magnetic head 16 faces the disk surface with a gap maintained between them. In this state, the read head 54 reads recorded information from the magnetic disk 12, and the write head 58 writes information to it.

[0030] When writing information, the drive voltage supply circuit 82 of the head amplifier IC 30, under the control of the MPU 46, applies a bias voltage to the main pole 60 and trailing shield 62, thereby passing a drive current in series through the connection terminal 45, wiring, main pole 60, STO 65, and trailing shield 62. The drive current flows in a direction perpendicular to the layer plane of the STO 65. The STO 65 oscillates spin torque, generating a high-frequency magnetic field that is applied to the magnetic recording layer 103 of the magnetic disk 12. At the same time, the write current supply circuit 81 of the head amplifier IC 30 passes write currents through the first and second write coils 70 and 72 in accordance with the write signal and write pattern generated by the R / W channel 42. The first and second write coils 70 and 72 excite the main pole 60 to generate a write magnetic field, which applies a write magnetic field perpendicular to the main pole 60 to the magnetic recording layer 103 of the magnetic disk 12 directly below. This records information on the magnetic recording layer 103 with the desired track width. Superimposing the high-frequency magnetic field of the STO 65 on the write magnetic field promotes magnetization reversal in the magnetic recording layer 103, enabling magnetic recording with high magnetic anisotropy energy.

[0031] FIG. 7 is a diagram showing the relationship between the ambient temperature and the element life, and FIG. 8 is a diagram showing the relationship between the element protrusion amount and the temperature rise of the element portion. As shown in Figure 7, in the HDD 10 described above, the lifespan of the assist element of the magnetic head 16 (here, STO65) tends to shorten as the element temperature (ambient temperature) increases, based on the Arrhenius equation. Therefore, if there is variation in the amount of heat generated by the assist element when a drive voltage is applied, there will be variation in the element lifespan. Also, as shown in Figure 8, there is a correlation between the element temperature and the protrusion amount of the assist element, and the protrusion amount tends to increase as the element temperature increases. Therefore, according to this embodiment, the controller adjusts the element drive voltage based on the protrusion amount of the assist element, thereby executing control to reduce variations in heat generation in the element portion.

[0032] FIG. 9 is a flowchart showing a procedure for setting the drive voltage of the assist element in the HDD 10. As shown in FIG. For example, the HDD 10 measures and sets the drive voltage of the assist element at the time of shipment, at regular intervals, or after each recording operation. In this embodiment, the HDD 10 adjusts and sets the drive voltage of the assist element based on the protrusion amount of the assist element. That is, the HDD 10 sets a drive voltage for each assist element that will result in a target protrusion amount (target protrusion amount value), thereby avoiding a situation in which the protrusion amount and heat generation amount vary greatly. An example of the setting operation will be described in detail.

[0033] 9, the main controller 40 of the HDD 10 first seeks the magnetic head 16 to a predetermined track position (ST1), and then applies an initial set value of heater power to the first heater (write heater) 76a of the magnetic head 16 (ST2). Next, the main controller 40 turns off the supply of bias voltage to the STO 65, and increases (raises) the heater power applied to the first heater 76a by the heater voltage supply circuit 83 (ST3). This causes the ABS 13 of the magnetic head 16 to bulge toward the surface of the magnetic disk 12, increasing the amount of protrusion (bulge amount). The main controller 40 detects whether the ABS 13 of the magnetic head 16 has come into contact with the magnetic disk 12 (ST4), and stops increasing the heater power when the contact detection circuit 85 detects contact (ST5). The main controller 40 stores in the memory 43 the heater power value P1 when the magnetic head 16 first comes into contact with the magnetic disk (recording medium) 12 (ST6). The contact of the magnetic head can be detected by detecting the rotational fluctuation of the magnetic disk 12 or by an HDI sensor provided on the magnetic head.

[0034] Next, the main controller 40 reduces the heater power value supplied to the first heater 76a from P1 by an amount corresponding to the protrusion amount target value (target value) PT of the assist element (ST7). That is, by reducing the heater power value, the protrusion amount of the magnetic head 16 is reduced, and the magnetic head 16 is displaced from the position where it abuts on the magnetic disk 12 to a position where it is lifted by the protrusion amount target value (target value) PT. Note that by measuring the relationship between the signal strength of the signal read by the read head and the lift amount of the magnetic head in advance, the lift amount of the magnetic head 16 can be accurately set to the protrusion amount target value PT based on the signal strength of the read head. The main controller 40 stops reducing the heater power value when the lift amount of the magnetic head 16 reaches the protrusion amount target value PT and saves the heater power value P2 at that time.

[0035] Next, the main controller 40 applies a bias voltage (drive voltage) to the STO 65 by the drive voltage supply circuit 82, and gradually increases (pull up) the bias voltage (ST8). As a result, the STO 65 (assist element) bulges toward the surface of the magnetic disk 12, and the protrusion amount (bulging amount) increases. The main controller 40 detects whether the assist element has come into contact with the magnetic disk 12 (ST9), and stops increasing the drive voltage when contact is detected by the contact detection circuit 85 (ST10). The main controller 40 sets the drive voltage value when the assist element first comes into contact with the magnetic disk (recording medium) 12 as the drive voltage of the assist element and saves this in memory 43 (ST11). That is, since the assist element comes into contact with the magnetic disk when the protrusion amount reaches the target value PT, by setting the drive voltage value at the time of contact as the drive voltage BT of the assist element, it is possible to align the protrusion amount when the assist element is driven with the target value PT. This completes the process of setting the drive voltage of the assist element. Thereafter, during a write operation of the HDD, the main controller 40 drives the assist element (STO 65) with the set drive voltage BT stored in the memory 43.

[0036] As described above, by adjusting the drive voltage value of the assist element in each magnetic head 16 so that the protrusion amount of the assist element when the drive voltage is applied becomes the desired protrusion amount PT, it is possible to suppress variations in the protrusion amount of the assist element and variations in the amount of heat generated. FIG. 11 shows the distribution of element lifespans resulting from a degradation test conducted for up to 2000 hours in a high-temperature environment of 60°C for the HDD according to the present embodiment and the HDD according to the comparative example. Note that in the HDD according to the comparative example, the drive voltage of the assist element is set to a fixed initial value. As shown in the figure, the element lifespans of degraded HDDs in the comparative example are dispersed over a wide range of 550 to 2000 hours, with some downward fluctuation. In contrast, in the HDD according to the present embodiment, the element lifespans are concentrated in a high range of 1400 to 2000 hours, with the downward fluctuation of the lifespan suppressed. In other words, the HDD according to the present embodiment can suppress the degradation of the assist element due to variations in heat generation, thereby extending the element lifespan.

[0037] As mentioned above, the assist element generates heat when a drive voltage is applied. As a result, the recording head portion located around the assist element heats up, increasing its protrusion (bulge). This can cause fluctuations in the flying height of the magnetic head. Therefore, in the HDD according to this embodiment, the flying height of the magnetic head is adjusted taking into account fluctuations in the flying height due to heat generation by the assist element. The operation of measuring and adjusting the flying height of the magnetic head will be described below.

[0038] After setting the drive voltage of the assist element as described above, the main controller 40 measures and adjusts the distance (gap) between the magnetic head 16 and the surface of the magnetic disk 12 (sometimes referred to as the flying height or back-off amount (BO)). FIG. 10 is a flow chart that schematically shows the operation of measuring and adjusting the flying height. As shown in the figure, the main controller 40 of the HDD 10 first seeks the magnetic head 16 to a predetermined track position (ST1), and then applies an initial setting value of heater power to the first heater (write heater) 76a of the magnetic head 16 (ST2). Next, while applying the set drive voltage BT to the assist element (ST065), the main controller 40 increases (raises) the heater power applied to the first heater 76a by the heater voltage supply circuit 83 (ST3). This increases the protrusion amount of the ABS 13 of the magnetic head 16.

[0039] The main controller 40 detects whether the ABS 13 of the magnetic head 16 has come into contact with the magnetic disk 12 (ST4), and stops increasing the heater power when contact is detected by the contact detection circuit 85. The main controller 40 stores in the memory 43 the heater power value P1 when the magnetic head 16 first comes into contact with the magnetic disk (recording medium) 12 (ST5). Next, the main controller 40 reduces the write heater power value from the heater power value P1 by the target value (target value) of the flying height of the magnetic head 16 (ST6), and stores this reduced write heater power value in the memory 43 as the write heater power setting value FT (ST17). During a write operation by the magnetic head 16, the main controller 40 applies a drive voltage to the assist element and also applies a set value FT of write heater power to the first heater 76a from the heater voltage supply circuit 83. As a result, even when the assist element is being driven, the flying height of the magnetic head 16 is set to the target value (aimed value).

[0040] According to the HDD of the first embodiment configured as described above, by detecting the protrusion amount due to heat generation of the assist element portion and adjusting the drive voltage (bias voltage) so as to obtain the desired protrusion amount, it is possible to avoid a situation in which the protrusion amount is large and the amount of heat generated varies greatly, and to avoid deterioration of the assist element due to heat generation of the element portion. As a result, according to this embodiment, it is possible to provide a disk device that can reduce deterioration of the assist element due to heat generation of the element portion.

[0041] Next, an HDD according to another embodiment will be described. In the following embodiments, the same parts as those in the first embodiment will be given the same reference numerals as those in the first embodiment, and detailed descriptions thereof may be omitted or simplified. (Second embodiment) Fig. 12 is a diagram showing the relationship between the temperature inside the device, the protrusion amount of the element portion, and the target value in a hard disk drive (HDD) according to the second embodiment. Fig. 13 is a cross-sectional view of the print head, schematically showing the relationship between the protrusion amount of the print head and the protrusion amount of the assist element in the HDD according to the second embodiment.

[0042] In the magnetic head 16, the life of the assist element depends on the temperature of the element. Therefore, as shown in Fig. 12, it is desirable to change the target value (target value) of the protrusion amount of the assist element depending on the temperature inside the device (ambient temperature). Therefore, the HDD according to the second embodiment is configured to execute control by adding the change in the temperature inside the device (ambient temperature) as one of the parameters in setting the drive voltage of the above-mentioned assist element.

[0043] As shown in Figure 13(a), the protrusion amount PT of an assist element (for example, STO65) due to self-heating caused by application of a bias voltage is the protrusion amount expanding from the assist element (heat source) and its surrounding area. The target value PT due to the self-heating temperature is given by the following, where the heat temperature is T (K), the height of the assist element (STO65) is SH (nm), and the linear expansion coefficient of the assist element is α (1 / K): PT=α·SH·T …(1) It is expressed as:

[0044] As shown in Figure 13(b), when the temperature inside the device rises by ΔT, the protrusion amount of the print head part including the element part increases by ΔL. Therefore, when the temperature inside the device rises by ΔT, the target value of the protrusion amount of the assist element by applying a bias voltage is ΔPT=α·SH·ΔT …(2) That is, the adjustment is made so that the temperature is reduced by (PT-ΔPT).

[0045] As an example, the linear expansion coefficient is approximately 12[10 -6 / K], when the average element height SH is 50 nm, the target value PT of the protrusion amount of the element part is adjusted as shown in Figure 12 according to the temperature inside the equipment.

[0046] According to the second embodiment, in step ST7 of the drive voltage setting operation shown in Fig. 9, the main controller 40 detects a change in the room temperature, a rise ΔT, based on a detection signal from the temperature sensor S1 (see Fig. 1), calculates ΔPT using the detected ΔT and the above equation (2), and further calculates (PT - ΔPT) and stores it in memory 43. Next, the main controller 40 reduces the write heater power value by the target protrusion value (PT - ΔPT) and flies the magnetic head 16 by (PT - ΔPT). Subsequently, the main controller 40 sets the element drive voltage value BT by executing steps ST8 to ST11 of the drive voltage setting operation shown in Fig. 9.

[0047] In the HDD according to the second embodiment configured as described above, when adjusting the drive voltage (bias voltage) so that the protrusion amount due to heat generation of the assist element unit is the desired target value, it is possible to set the element drive voltage appropriate for the temperature inside the device by taking into account the change in the temperature inside the device. As a result, even in the second embodiment, it is possible to provide a disk device that can reduce the deterioration of the assist element due to heat generation of the element unit.

[0048] (Third embodiment) The HDD according to the third embodiment is configured such that when setting the flying height of the magnetic head and the drive voltage of the assist element, the set value of the element drive voltage is adjusted according to the radial position of the magnetic head relative to the magnetic disk. Fig. 14 is a plan view showing different radial positions of the magnetic head relative to the magnetic disk in an HDD according to a third embodiment, Fig. 15 is a plan view showing the skew state of the magnetic head at different radial positions, Fig. 16 is a diagram showing the relationship between the initial flying height of the magnetic head and the target protrusion value of the element unit in an HDD according to the third embodiment, and Fig. 17 is a diagram showing the relationship between the radial position of the magnetic head and the initial flying height of the magnetic head in an HDD.

[0049] As shown in Figures 14 and 15, depending on the radial position of the magnetic head 16 relative to the magnetic disk 12 (inner peripheral position IN, middle peripheral position M, outer peripheral position OUT), the wind speed of the gas flowing into the slider of the magnetic head 16 and the wind angle due to the influence of the skew of the magnetic head 16 change, and the lift of the magnetic head 16 fluctuates. 15, the magnetic head 16 positioned at the inner radial position IN has a large skew and a small airflow, while the magnetic head 16 positioned at the middle radial position M has a zero skew and a medium airflow. The magnetic head 16 positioned at the outer radial position Out has a large skew and a large airflow. Therefore, the lift acting on the ABS 13 of the magnetic head 16 varies depending on the radial position of the magnetic head, and the initial flying height of the magnetic head when no heater power is applied varies depending on the radial position. In this case, the heater power applied to the heater so that the magnetic head achieves a predetermined flying height and the heat generation amount of the element due to the application of heater power also vary depending on the radial position, so it is desirable to adjust the target value of the element protrusion amount depending on the initial flying height.

[0050] When the initial flying height fluctuates by ΔFH [nm], the heat generation ΔT [K] of the element part by the heater is expressed as follows, assuming that the yoke length of the largest head pole (e.g., trailing shield pole 62) is L1 [nm] (see Figures 3 and 13) and the linear expansion coefficient of the head electrode yoke is β [1 / K]: ΔFH=β·L1·ΔT …(3) It is expressed as:

[0051] On the other hand, as shown in the above formula (2), when the temperature of the element (temperature inside the device) rises by ΔT, it is desirable to reduce the target value PT of the element protrusion due to the application of bias voltage by ΔPT = α·SH·ΔT. Therefore, the change in protrusion ΔPT when the initial flying height changes by ΔFH [nm] is ΔPT = -(α / β)·(SH / L)·ΔFH ... (4). As an example, if the assist element is a high-frequency assist element whose main component is an oscillation layer made of FeCo, which is similar to the head pole material, then α / β can be considered to be 1. Therefore, if the average element height SH is 50 nm and the yoke length L1 is 2000 nm, the target protrusion value PT is adjusted by the initial flying height, as shown in FIG. 16.

[0052] According to the third embodiment, in step ST7 of the drive voltage setting operation shown in FIG. 9, the main controller 40 detects a change in room temperature, or rise ΔT, based on a detection signal from the temperature sensor S1 (see FIG. 1), and detects the radial position of the magnetic head 16 based on the servo data. The main controller 40 calculates a change in initial flying height ΔFH based on the radial position of the magnetic head 16 and the above equation (3). Next, the main controller 40 calculates ΔPT using ΔT, ΔFH, and equation (4), and further calculates a target value (PT-ΔPT) and stores it in memory 43. Next, the main controller 40 reduces the write heater power value by the protrusion target value (PT-ΔPT) and flies the magnetic head 16 by (PT-ΔPT). Next, the main controller 40 sets the element driving voltage value BT by executing steps ST8 to ST11 of the drive voltage setting operation shown in FIG. 9.

[0053] In the HDD according to the third embodiment configured as described above, the protrusion amount due to heat generation of the assist element unit is detected, and when adjusting the drive voltage (bias voltage) to achieve the desired protrusion amount, it is possible to set an element drive voltage appropriate for the temperature inside the device and the radial position by taking into account changes in the temperature inside the device and the radial position of the magnetic head. As a result, even in the third embodiment, it is possible to provide a disk device that can reduce deterioration of the assist element due to heat generation of the element unit.

[0054] In the first, second, and third embodiments described above, the assist element of the magnetic head is not limited to a high-frequency oscillation element such as STO, and other assist elements can be applied. Below, modified examples using other assist elements will be described. (First Modification) FIG. 18 is a plan view of the recording head of the magnetic head according to the first modification, viewed from the ABS side. As shown in the figure, according to the first modification, the magnetic head includes a write assist element 90 as an assist element. The write assist element 90 is primarily composed of multiple layers of nonmagnetic conductive materials, such as NiCr, Ru, Ta, or Cu. The write assist element 90 is provided between the tip 60a of the main pole 60 and the tip 62a of the trailing shield 62, and between the tip of the side shield 63 and the tip 62a of the trailing shield 62. At the ABS 13 of the magnetic head, the width WS of the write assist element 90 in the cross-track direction CT is larger than the width of the trailing-side end face 60b of the main pole 60. Both ends of the write assist element 90 in the cross-track direction CT are sandwiched between the side shield 63 and the trailing shield 62, respectively. The lower end surface of the write assist element 90 is exposed to the ABS 13 and extends substantially flush with the ABS 13.

[0055] The main pole 60, trailing shield 62, and side shield 63 are connected by wiring to the head amplifier IC 30 and main controller 40, respectively. A current circuit is configured to pass an element drive current (bias voltage) in series from the head amplifier IC 30 through the main pole 60, write assist element 90, trailing shield 62, and side shield 63. When writing information, the drive voltage supply circuit 82 (see FIG. 1) of the head amplifier IC 30, under the control of the MPU 46, applies a bias voltage to the main pole 60, trailing shield 62, and side shield 63, thereby passing a drive current through the write assist element 90. This causes the write assist element 90 to generate a current magnetic field. The generated current magnetic field can improve the magnetization response of the write magnetic flux generated from the main pole 60.

[0056] The above-described write assist element 90 generates heat when a drive voltage is applied, and bulges out so as to protrude toward the magnetic disk. When any of the first to third embodiments described above is applied, the main controller of the HDD adjusts the element drive voltage based on the protrusion amount of the write assist element 90, thereby reducing variations in heat generation in the element portion and suppressing deterioration of the assist element.

[0057] (Second Modification) FIG. 19 is an enlarged cross-sectional view of a head portion of a magnetic head according to a second modified example. As shown in the figure, according to the second modified example, the magnetic head 16 includes a thermally assisted element as an assist element. In one example, the thermally assisted element includes a near-field light generating element (optical element) 98 disposed near the main pole 60 on the leading side of the main pole 60, a laser diode 94 functioning as a light source, and a waveguide 96 that propagates light (laser light) emitted from the laser diode 94 to the near-field light generating element 98. An exit surface 98a of the near-field light generating element 98 is exposed to the ABS 13 of the magnetic head 16 and faces the magnetic disk 12. When the near-field light generating element 98 receives the laser light, it generates near-field light and heats the recording layer 103 of the magnetic disk 12. In this modified example, the term "nearby" refers to, for example, a range of 10 to 100 nm from the main pole 60.

[0058] A drive voltage is applied to the laser diode 94 from the drive voltage supply circuit 82 (see FIG. 1) of the head amplifier IC, causing the laser diode 94 to generate laser light. The generated laser light is input to a waveguide 96 and supplied to a near-field light generating element 98 through this waveguide 96. This causes the near-field light generating element 98 to generate near-field light, which is irradiated from an emission surface 98a toward the magnetic disk 12. The near-field light locally heats the recording layer 103 of the magnetic disk 12, creating a recording region where local magnetization reversal is likely to occur, i.e., an area where information can be easily recorded, enabling high-density recording and high-capacity recording.

[0059] The near-field light generating element (optical element) 98 described above generates heat when supplied with laser light, and bulges out so as to protrude toward the magnetic disk. When any of the first to third embodiments described above is applied, the main controller of the HDD adjusts the set value of the drive voltage applied to the light source (laser diode 94) based on the protrusion amount of the near-field light generating element 98, thereby reducing variations in heat generation of the near-field light generating element and suppressing deterioration of the near-field light generating element.

[0060] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. For example, the recording head according to the embodiment can also be applied to a recording head that does not have a leading shield and / or side shield. In the case of a recording head that has a leading shield, the assist element can also be disposed in the gap between the main pole and the leading shield. In addition, the material, shape, size, etc. of the elements that make up the head portion of the magnetic head can be changed as needed. In a magnetic disk drive, the number of magnetic disks and magnetic heads can be increased or decreased as needed, and various sizes of magnetic disks can also be selected. [Explanation of symbols]

[0061] 10...magnetic disk device, 11...casing, 12...magnetic disk, 16...magnetic head, 30...head amplifier IC, 40...main controller, 60...main pole, 62...trailing shield (right shield pole), 63...side shield, 64...leading shield, 65...spin torque oscillator (high frequency oscillator element), 76a...first heater, 76b...second heater, 81...recording current supply circuit, 82...drive voltage supply circuit, 83...heater voltage supply circuit, 85...contact detection circuit, 90...light assist element, 98... Near-field light generating element (optical element) S1... Temperature sensor

Claims

1. a rotatable disk-shaped recording medium having a magnetic recording layer; a magnetic head including a write head having a main pole that generates a recording magnetic field, a write shield pole that faces the main pole across a write gap, and a coil that excites magnetic flux; an assist element; and a heater that heats the write head; a controller including a heater voltage supply circuit that supplies heater power to the heater, a drive voltage supply circuit that supplies a drive voltage to the assist element, and a contact detection circuit that detects contact between the magnetic head and the recording medium, and that adjusts a set value of the drive voltage based on the protrusion amount of the assist element when contact is detected by the contact detection circuit; A disk device comprising:

2. 2. The disk device of claim 1, wherein the controller performs the following operations: increasing the heater power supplied to the heater from the heater voltage supply circuit while the drive voltage of the assist element is turned off; stopping the increase in the heater power when contact between the magnetic head and the recording medium is detected for the first time by the contact detection circuit; reducing the power value of the heater power when contact between the magnetic head and the recording medium is detected for the first time by a desired element protrusion amount; increasing the drive voltage supplied to the assist element from the drive voltage supply circuit; and stopping the increase in the drive voltage when contact between the magnetic head and the recording medium is detected for the first time by the contact detection circuit, and setting the drive voltage value at that time to the set value.

3. the controller includes a temperature sensor for measuring an internal temperature of the device; 2. The disk drive according to claim 1, wherein the set value is adjusted in response to a change in the temperature inside the disk drive detected by the temperature sensor.

4. 4. The disk device according to claim 3, wherein the set value decreases as the internal temperature of the device detected by the temperature sensor increases.

5. 2. The disk drive according to claim 1, wherein the controller has the setting value adjusted according to the radial position of the magnetic head.

6. 6. The disk drive according to claim 5, wherein the set value is smaller as the initial flying height of the magnetic head is larger.

7. 2. The disk drive according to claim 1, wherein the assist element includes a high-frequency assist element provided between the main pole and the write shield pole within the write gap.

8. the magnetic head has a side shield facing the main pole with a gap therebetween, 2. The disk drive according to claim 1, wherein the assist element includes a write assist element provided between the main pole and the write shield pole, and between the main pole and the side shield.

9. the assist element includes an optical element provided next to the main pole, a light source that oscillates a laser beam, and a waveguide that guides the laser beam to the optical element; 2. The disk device according to claim 1, wherein the drive voltage supply circuit supplies a drive voltage to the light source.

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