Disk device

Abstract

The present invention provides a disk device capable of suppressing deterioration of a magnetic head to improve reliability. According to an embodiment, the disk device includes: a disk-shaped recording medium (12) that rotates freely; a magnetic head (16) having a write head with a main magnetic pole for applying a recording magnetic field to the recording medium, an auxiliary element for assisting magnetic recording using the main magnetic pole, and a plurality of thermal actuators for controlling the head tilt with respect to the recording medium; and a magnetic controller (40) having a detection unit (46a, 46c) for detecting deterioration of the head, and changing the head tilt of the magnetic head by the thermal actuator according to the detected deterioration.

Description

[0001] Related Application

[0002] This application claims priority based on Japanese Patent Application No. 2021-142663 (filing date: September 1, 2021). This application incorporates all the contents of the base application by reference thereto. Technical Field

[0003] Embodiments of the present invention relate to a disk device. Background Art

[0004] As a magnetic recording and reproducing device, for example, a disk device has a disk-shaped recording medium that rotates freely and a magnetic head that records and reproduces data on the magnetic recording layer of the recording medium. The magnetic head has a slider, a reproducing head provided on the slider, and a recording head. In order to increase the recording density, particularly the linear recording density, a magnetic head with an auxiliary recording function has been proposed.

[0005] In a magnetic head with an auxiliary recording function, the main cause of head characteristic deterioration is the development of oxidation due to wear of the protective film. The reason is considered to be that the oxidation of the magnetic material progresses due to wear of the protective film during recording and reproduction when the flying height of the magnetic head decreases, as well as heat generation caused by the auxiliary recording operation. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a disk device that can suppress the deterioration of the magnetic head and improve reliability.

[0007] According to an embodiment, a disk device includes: a disk-shaped recording medium that rotates freely; a magnetic head having a writing head with a main magnetic pole that applies a recording magnetic field to the recording medium, an auxiliary element that assists magnetic recording using the main magnetic pole, and a plurality of thermal actuators that control the head tilt with respect to the recording medium; and a controller having a detection unit that detects deterioration of the magnetic head, and changing the head tilt of the magnetic head by the thermal actuators based on the detected deterioration. Brief Description of the Drawings

[0008] Figure 1 is a block diagram schematically showing a hard disk drive (HDD) according to the first embodiment.

[0009] Figure 2 is a side view schematically showing a magnetic head, a suspension, and a disk in the HDD.

[0010] Figure 3 is an enlarged cross-sectional view showing the head portion of the magnetic head.

[0011] Figure 4 is an enlarged cross-sectional view showing the tip portion of the recording head.

[0012] Figure 5 It is a cross-sectional view that magnifies and shows the tip of the recording head.

[0013] Figure 6 It is a flowchart showing the deterioration suppression processing operation of the magnetic head during magnetic recording.

[0014] Figure 7 It is a side view schematically showing the magnetic head of the HDD of the second embodiment.

[0015] Figure 8 It is a side view schematically showing the magnetic head of the HDD of the third embodiment.

[0016] Figure 9 It is a side view schematically showing the magnetic head of the HDD of the fourth embodiment.

[0017] Figure 10 It is a side view schematically showing the magnetic head of the HDD of the fifth embodiment.

[0018] Figure 11 It is a cross-sectional view that magnifies and shows the tip of the recording head in the fifth embodiment.

[0019]

Explanation of Reference Numerals

[0020] 10... Disk device, 11... Cartridge, 12... Disk, 13... ABS, 15... Slider, 16... Magnetic head, 17... Head, 30... Head amplifier IC, 40... Main controller, 54... Reproduction head, 58... Recording head, 60... Main magnetic pole, 62... Tail shield, 64... Leading shield, 65... Flux control layer, 76a... First heater (first thermal actuator), 76b... Second heater (second thermal actuator), 76c... Third heater (third thermal actuator), WG... Write gap Detailed Embodiments

[0021] Hereinafter, with reference to the drawings, the disk device of the embodiment will be described.

[0022] In addition, the disclosure is merely an example, and what can be appropriately changed and easily conceived by those skilled in the art under the gist of the invention is of course included in the scope of the present invention. Further, for the sake of clearer explanation, in the drawings, the widths, thicknesses, shapes, etc. of each part are sometimes schematically shown compared to the actual situation, but this is merely an example and is not used to limit the interpretation of the present invention. In addition, in this specification and each drawing, the same elements mentioned in the already mentioned drawings are given the same reference numerals and detailed descriptions are appropriately omitted.

[0023] (First Embodiment)

[0024] As an example of a disk device, the hard disk drive (HDD) of the first embodiment will be described in detail. Figure 1 is a block diagram schematically showing the HDD of the first embodiment, Figure 2 and is a side view showing the head in a floating state and the disk.

[0025] As shown in Figure 1 , the HDD 10 has a rectangular box 11, a disk 12 as a recording medium disposed within the box 11, a spindle motor 14 that supports and rotates the disk 12, and a plurality of heads 16 that record (write) and reproduce (read) data on the disk 12. The HDD 10 has a head actuator 18 that moves and positions the heads 16 on any track (orbit) on the disk 12. The head actuator 18 has a carriage assembly 20 that movably supports the heads 16 and a voice coil motor (VCM) 22 that rotates the carriage assembly 20.

[0026] The HDD 10 has a head amplifier IC 30, a main controller 40, and a driver IC 48 that drive the heads 16. The head amplifier IC 30 is provided, for example, on the carriage assembly 20 and is electrically connected to the heads 16. The head amplifier IC 30 has: a recording current supply circuit (recording current supply unit) 32 that supplies a recording current to the recording coils of the heads 16; an STO current supply circuit 31 that supplies a drive current to a spin torque oscillator (STO) serving as a magnetic flux control layer described later; a first heater power supply circuit 34a and a second heater power supply circuit 34b that supply drive power to a thermal actuator (heater) of the heads 16 described later; and an amplifier (not shown) that amplifies a signal read by the heads.

[0027] The main controller 40 and the driver IC 48 are formed, for example, on a control circuit board (not shown) provided on the back side of the box 11. The main controller 40 has an R / W channel 42, a hard disk controller (HDC) 44, a microprocessor (MPU) 46, a memory 47, and the like. The main controller 40 is electrically connected to the heads 16 via the head amplifier IC 30. The main controller 40 is electrically connected to the VCM 22 and the spindle motor 21 via the driver IC 48. The HDC 44 can be connected to the host 45.

[0028] The R / W channel 42 is a signal processing circuit for reading / writing data. The HDC 44 constitutes an interface between the HDD 10 and the host 45 and executes transmission control of reading / writing data. The memory 47 includes a cache composed of DRAM, a flash memory, and the like. In the memory 47, a heater power setting table 47a described later, initial value data 47b including an initial resistance value of the STO and an initial value of a bit error rate, and the like are stored.

[0029] The MPU 46 is the main control unit of the disk drive, and executes control for read / write operations and servo control required for positioning of the head. Further, the MPU 46 executes power-on control of the STO and power-on control of the thermal actuator. The detailed configuration of the MPU 46 will be described later.

[0030] As Figure 1 and Figure 2 shown, the magnetic disk 12 is configured as a perpendicular magnetic recording medium. The magnetic disk 12 has, for example, a substrate 101 made of a non-magnetic material and formed in a disc shape with a diameter of 96 mm (about 3.5 inches). On each surface of the substrate 101, a soft magnetic layer 102 made of a material showing soft magnetic properties and serving as a base layer, 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 laminated in this order. The magnetic disk 12 is coaxially fitted with the hub of the spindle motor 21. The magnetic disk 12 is rotated at a predetermined speed in the direction of arrow B by the spindle motor 21.

[0031] The carriage assembly 20 has a bearing portion 24 rotatably supported by the housing 11 and a plurality of suspensions 26 extending from the bearing portion 24. As Figure 2 shown, the head 16 is supported at the extending end of each suspension 26. The head 16 is electrically connected to the head amplifier IC 30 via a wiring member (flexible member) 28 provided in the carriage assembly 20.

[0032] As Figure 2 shown, the head 16 is configured as a floating head, and has a slider 15 formed in a substantially rectangular parallelepiped shape and a head 17 formed at an end on the outflow end (trailing end) side of the slider 15. The slider 15 is formed of, for example, a sintered body of alumina and titanium carbide (alumina / titanium carbide), and the head 17 is formed of a multilayer thin film. The slider 15 is mounted on the gimbal portion 28a of the wiring member 28.

[0033] The slider 15 has a substantially rectangular disk facing surface (air bearing surface (ABS)) 13 facing the surface of the magnetic disk 12. The slider 15 is maintained in a state of floating a predetermined amount from the surface of the magnetic disk 12 by an air flow C generated between the disk surface and the ABS 13 due to the rotation of the magnetic disk 12. The direction of the air flow C is the same as the rotation direction B of the magnetic disk 12. The slider 15 has a leading end 15a on the inflow side of the air flow C and a trailing end 15b on the outflow side of the air flow C. As the magnetic disk 12 rotates, the head 16 travels in the direction of arrow A (head traveling direction) with respect to the magnetic disk 12, that is, in a direction opposite to the rotation direction B of the disk.

[0034] Further, in a state where the head 16 is floating, the ABS 13 of the slider 15 is inclined at a first pitch angle (tilt angle) D1 with respect to the surface of the magnetic disk 12.

[0035] Figure 3 It is a cross-sectional view showing an enlarged head 17 of the magnetic head 16 and the magnetic disk 12.

[0036] As Figure 3 shown, the head 17 has a reproducing head (read head) 54 and a recording head (write head) 58 formed at the trailing end 15b of the slider 15 by a thin film process, and is formed as a separated magnetic head. The reproducing head 54 and the recording head 58 are covered by 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 17. Further, the head 17 has a first thermal actuator for controlling the protrusion amount of the recording head 58 and a second thermal actuator for controlling the protrusion amount of the reproducing head 54. The first thermal actuator has, for example, a first heater 76a which is buried in the protective insulating film 53 and is located near the recording head 58. The second thermal actuator is provided away from the first heater 76a and has, for example, a second heater 76b which is buried in the protective insulating film 53 and is located near the reproducing head 54.

[0037] The length direction of the recording track formed on the perpendicular magnetic recording layer 103 of the magnetic disk 12 is defined as the downtrack direction DT along the track, and the width direction of the recording track orthogonal to the length direction is defined as the across-track direction WT.

[0038] The reproducing head 54 has a magnetoresistive effect element 55, and a first magnetic shielding film 56 and a second magnetic shielding film 57 which are arranged on the leading side (inflow side) and the trailing side (outflow side) of the magnetoresistive effect element 55 in the downtrack direction DT so as to sandwich the magnetoresistive effect element 55. The magnetoresistive effect element 55, the first shielding film 56 and the second magnetic shielding film 57 extend substantially perpendicular to the ABS 13. The lower ends (top ends) of the magnetoresistive effect element 55, the first shielding film 56 and the second magnetic shielding film 57 slightly protrude from the ABS 13.

[0039] The recording head 58 is provided on the trailing end 15b side of the slider 15 with respect to the reproducing head 54. The recording head 58 has: a main magnetic pole 60 that generates a recording magnetic field in a direction perpendicular to the surface of the magnetic disk 12; a trailing shield (first shield) 62 provided on the trailing end side of the main magnetic pole 60 and facing the main magnetic pole 60 across a write gap; a leading shield (second shield) 64 facing the leading side of the main magnetic pole 60; and a pair of side shields (not shown) that are integrally formed with the trailing shield 62 and are provided on both sides of the main magnetic pole 60 in the across-track direction CT. The main magnetic pole 60 and the trailing shield 62 constitute a first magnetic core forming a magnetic circuit, and the main magnetic pole 60 and the leading shield 64 constitute a second magnetic core forming a magnetic circuit. The recording head 58 has a first recording coil 70 wound around the first magnetic core and a second recording coil 72 wound around the second magnetic core.

[0040] The main magnetic pole 60 is formed of a soft magnetic material having a high magnetic permeability and a high saturation magnetic flux density, and extends substantially perpendicular to the ABS 13. The tip portion 60a on the ABS 13 side of the main magnetic pole 60 tapers toward the ABS 13 and is formed into a columnar shape with a width narrower than that of other portions. The tip portion 60a of the main magnetic pole 60 slightly protrudes from the ABS 13 of the slider 15.

[0041] The trailing shield 62 is formed of a soft magnetic material and is provided to efficiently close the magnetic circuit through the soft magnetic layer 102 of the magnetic disk 12 directly below the main magnetic pole 60. The trailing shield 62 is formed in a substantially L shape, and its tip portion 62a is formed in an elongated rectangular shape. The tip portion 62a of the trailing shield 62 slightly protrudes from the ABS 13 of the slider 15. The tip portion 62a has a leading side end face (magnetic pole end face) 62b that faces the tip portion 60a of the main magnetic pole 60 with the write gap WG therebetween. The leading side end face 62b extends perpendicular to or slightly inclined with respect to the ABS 13.

[0042] The trailing shield 62 has a first connection portion 50 that connects to the main magnetic pole 60. The first connection portion 50 is magnetically connected to the upper portion of the main magnetic pole 60, that is, the portion of the main magnetic pole 60 that is separated from the ABS 13, via a non-conductive body 52. In the first magnetic core, the first recording coil 70 is wound around the first connection portion 50, for example. When writing a signal to the magnetic disk 12, a recording current flows through the first recording coil 70, so that the first recording coil 70 excites the main magnetic pole 60 and causes magnetic flux to flow in the main magnetic pole 60.

[0043] The leading shield 64 formed of a soft magnetic material is provided opposite to the main magnetic pole 60 on the leading side of the main magnetic pole 60. The leading shield 64 is formed in a substantially L shape, and the tip portion 64a on the ABS 13 side is formed in an elongated rectangular shape. The tip portion 64a slightly protrudes from the ABS 13 of the slider 15. The tip portion 64a has a trailing side end face (magnetic pole end face) 64b that faces the tip portion 60a of the main magnetic pole 60 with a gap therebetween.

[0044] In addition, the leading shield 64 has a second connection portion 67 that engages with the main magnetic pole 60 at a position separated from the ABS 13. The second connection portion 67 is formed of a soft magnetic material, for example, and is magnetically connected to the upper portion of the main magnetic pole 60, that is, the portion of the main magnetic pole 60 that is separated from the ABS 13, via a non-conductive body 59. Thus, the second connection portion 67 forms a magnetic circuit together with the main magnetic pole 60 and the leading shield 64. The second recording coil 72 of the recording head 58 is wound around the second connection portion 67, for example, and a magnetic field is applied to the magnetic circuit.

[0045] Figure 4 It is a cross-sectional view that magnifies the tip portion of the recording head.

[0046] As shown in the figure, the recording head 58 has a flux control layer 65 disposed in the write gap WG between the top end portion 60a of the main magnetic pole 60 and the tail shield 62. The flux control layer 65 constitutes a spin torque oscillator (STO) that functions as a high-frequency auxiliary element. In addition, a protective layer 68 is provided to cover the end face on the ABS 13 side of the recording head 58 including the main magnetic pole 60, the flux control layer 65, and the tail shield 62.

[0047] The flux control layer 65 has a function of spin torque oscillation in such a way as to only suppress the inflow of magnetic flux from the main magnetic pole 60 to the tail shield 62, that is, to effectively make the magnetic permeability of the write gap WG negative. Specifically, the flux control layer 65 has: a conductive intermediate layer (first non-magnetic conductive layer) 65a, an adjustment layer 65b, and a conductive cover layer (second non-magnetic conductive layer) 65c. These layers are laminated in sequence from the main magnetic pole 60 side to the tail shield 62 side, that is, these layers are laminated in sequence along the track direction DT. The intermediate layer 65a, the adjustment layer 65b, and the conductive cover layer 65c each have a film surface parallel to the shield side end face 60c of the main magnetic pole 60, that is, extending in a direction intersecting the ABS 43.

[0048] In addition, the lamination direction of the intermediate layer 65a, the adjustment layer 65b, and the conductive cover layer 65c is not limited to the above, and may also be reversed, that is, laminated from the tail shield 62 side to the main magnetic pole 60 side.

[0049] The intermediate layer 65a can be formed, for example, of a metal layer such as Cu, Au, Ag, Al, Ir, NiAl alloy, etc., and a material that does not hinder spin conduction. The intermediate layer 65a is directly formed on the shield side end face 60c of the main magnetic pole 60. The adjustment layer 65b includes a magnetic material containing at least one of iron, cobalt, and nickel. As the adjustment layer 65b, for example, an alloy material obtained by adding at least one of Al, Ge, Si, Ga, B, C, Se, Sn, and Ni to FeCo, and at least one material selected from the artificial lattice group composed of Fe / Co, Fe / Ni, and Co / Ni can be used, etc. The thickness of the adjustment layer 65b can be set to, for example, 2 to 20 nm. The conductive cover layer 65c can be made of a non-magnetic metal and a material that blocks spin conduction. The conductive cover layer 65c can be formed, for example, of at least one selected from Ta, Ru, Pt, W, Mo, Ir, or an alloy including the at least one. The conductive cover layer 65c is directly formed on the leading side end face 62b of the tail shield 62. In addition, the conductive cover layer can be a single layer or multiple layers.

[0050] The intermediate layer 65a is formed to have a film thickness that transmits the self-rotation torque from the main magnetic pole 60 and has a sufficiently weak exchange interaction, for example, a film thickness of 1 to 5 nm. The conduction shield layer 65c only needs to have a film thickness that blocks the self-rotation torque from the tail shield 62 and has a sufficiently weak exchange interaction, for example, a film thickness of 1 nm or more.

[0051] Since the adjustment layer 65b needs to reverse the magnetization direction with the magnetic field by the self-rotation torque from the main magnetic pole 60, it is better if the saturation magnetic flux density of the adjustment layer 65b is small. On the contrary, in order to effectively shield the magnetic flux by the adjustment layer 65b, it is better if the saturation magnetic flux density of the adjustment layer 65b is large. Since the magnetic field between the write gaps WG is about 10 to 15 kOe, even if the saturation magnetic flux density of the adjustment layer 65b is about 1.5 T or more, it is difficult to improve the improvement effect. Therefore, it is desired that the saturation magnetic flux density of the adjustment layer 65b is 1.5 T or less. More specifically, it is desired that the product of the film thickness and the saturation magnetic flux density of the adjustment layer 65b is 20 nmT or less.

[0052] In order to make the current flow concentratedly in the direction perpendicular to the film surface of the intermediate layer 65a, the adjustment layer 65b, and the conduction shield layer 65c, the periphery of the magnetic flux control layer 65 is covered by an insulating layer, such as a protective insulating film 53, except for the portions in contact with the main magnetic pole 60 and the tail shield 62.

[0053] A base layer can also be provided between the main magnetic pole 60 and the intermediate layer 65a.

[0054] The base layer can be made of a metal such as Ta or Ru, for example. The thickness of the base layer can be set to, for example, 0.5 to 10 nm. Moreover, it can be set to about 2 nm.

[0055] Moreover, a cover layer can also be provided between the tail shield 62 and the conduction shield layer 65c.

[0056] As the cover layer, at least one non-magnetic element selected from the group consisting of Cu, Ru, W, and Ta can be used. The thickness of the cover layer can be set to, for example, 0.5 to 10 nm. Moreover, it can be set to about 2 nm.

[0057] In addition, CoFe can be used as the spin polarization layer between the main magnetic pole and the intermediate layer.

[0058] The main magnetic pole 60 can be formed of a soft magnetic metal alloy mainly composed of an Fe-Co alloy. The main magnetic pole 60 also functions as an electrode for applying current to the intermediate layer 65a. The tail shield 62 can be formed of a soft magnetic metal alloy mainly composed of an Fe-Co alloy. The tail shield 62 also functions as an electrode for applying current to the conduction shield layer 65c.

[0059] The protective layer 68 is provided to protect the ABS 13, and is composed of one or more materials and formed of a single layer or multiple layers. The protective layer 68 has, for example, a surface layer made of diamond-like carbon. A base layer made of, for example, Si or the like can also be provided between the ABS 13 of the recording head 58 and the protective layer 68.

[0060] As Figure 3 shown, the main magnetic pole 60 and the tail shield 62 are respectively connected to the connection terminal 43 via wiring, and further, the head amplifier IC 30 and the main controller 40 are connected via a wiring component (flexible member) 28. A current circuit is formed in which the STO drive current (bias voltage) is connected in series through the main magnetic pole 60, the STO 65, and the tail shield 62 from the STO current supply circuit 31 of the head amplifier IC 30.

[0061] The first recording coil 70 and the second recording coil 72 are respectively connected to the connection terminal 43 via wiring, and further, are connected to the head amplifier IC 30 via the flexible member 28. When writing a signal to the magnetic disk 12, the recording current flows from the recording current supply circuit 32 of the head amplifier IC 11 to the recording coils 70 and 72, thereby exciting the main magnetic pole 60 and causing magnetic flux to flow in the main magnetic pole 60. The recording current supplied to the recording coil 64 is controlled by the HDC 44.

[0062] The first heater 76a and the second heater 76b are respectively connected to the connection terminal 43 via wiring, and further, are connected to the head amplifier IC 30 via the flexible member 28. Desired heater power is supplied from the first heater power supply circuit 34a of the head amplifier IC 30 to the first heater 76a, and desired heater power is supplied from the second heater power supply circuit 34b to the second heater 76b. The power and power ratio supplied to the first heater and the second heater are controlled by the MPU 46.

[0063] According to the HDD 10 configured as described above, by driving the VCM 22, the actuator 18 is driven to rotate, and the magnetic head 16 is moved and positioned on a desired track of the magnetic disk 12. Further, as Figure 2 shown, the magnetic head 16 is floated by the air flow C generated between the disk surface and the ABS 13 due to the rotation of the magnetic disk 12. During the operation of the HDD, the ABS 13 of the slider 15 maintains a gap with respect to the disk surface and faces it in a state inclined at a predetermined angle. In this state, for the magnetic disk 1, the recorded information is read by the reproducing head 54, and information is written by the recording head 58.

[0064] The protrusion amount of the recording head 58, the protrusion amount of the reproducing head 54, and the inclination of the magnetic head 16 can be arbitrarily controlled by adjusting the power and power ratio (power ratio) supplied to the first heater 76a and the second heater 76b.

[0065] The first heater 76a and the second heater 76b are, for example, coil-shaped and generate heat when energized, causing thermal expansion of the surrounding area. As a result, the portions near the tips of the recording head 58 and the reproducing head 54 protrude from the ABS 13 toward the magnetic disk 12 side, reducing the distance from the magnetic disk 12 and lowering the flying height of the magnetic head 16. Thus, by adjusting the drive currents supplied to the first heater 76a and the second heater 76 respectively to control the calorific value, the flying height of the magnetic head 16 can be controlled. Additionally, by adjusting the energization ratio (power ratio) to the first heater 76a and the second heater 76b, the tilt angle (head skew) D1 of the magnetic head 16 with respect to the surface of the magnetic disk 12 can be adjusted. For example, when the energization ratio to the first heater 76a is decreased, the protrusion amount of the recording head 58 decreases and the flying height of the magnetic head 58 increases. As a result, the tilt angle D1 of the magnetic head 16 becomes smaller.

[0066] In the initial state of the HDD, power is supplied to the first heater 76a and the second heater 76b at a preset predetermined power ratio. As a result, the magnetic head 16 is tilted with respect to the magnetic disk 12 at a predetermined angle (head skew).

[0067] When the magnetic head 16 writes data, as Figure 3 and Figure 4 shown, under the control of the MPU 46 and the R / W channel 42, a recording current is supplied from the recording current supply circuit 32 to the first recording coil 70 and the second recording coil 72, thereby exciting the main magnetic pole 60 and applying a vertical recording magnetic field to the magnetic recording layer 103 of the magnetic disk 12 directly below the main magnetic pole 60. As a result, information is written to the magnetic recording layer 103 with a desired track width.

[0068] When applying a recording magnetic field to the disk 12, a driving current flows from the STO current supply circuit 31 through the main magnetic pole 60, the STO 65, and the trailing shield 62, so that the driving current is applied to the STO 65. By applying the current, a spin torque acts on the adjustment layer 65b of the STO 65 from the main magnetic pole 60, and the orientation of the magnetization of the adjustment layer 65b becomes the direction opposite to the orientation of the magnetic field (gap magnetic field) generated between the main magnetic pole 60 and the trailing shield 62. By this magnetization reversal, the adjustment layer 65b has the effect of shielding the magnetic flux (gap magnetic field) directly flowing from the main magnetic pole 60 to the trailing shield 62. As a result, the magnetic field leaking from the main magnetic pole 60 to the write gap WG is reduced, and the convergence degree of the magnetic flux from the tip 60a of the main magnetic pole 60 toward the magnetic recording layer 103 of the disk 12 is improved. That is, it is possible to make the magnetic flux flowing from the main magnetic pole 60 to the trailing shield 62 toward the disk (recording medium) 16 while keeping the write gap WG narrow. Thereby, the resolution of the recording magnetic field can be improved, and an increase in the recording track density can be achieved. In addition, the above example shows a mode in which the magnetization of the STO 65 is reversed by the action of the spin torque, but it may also include a mode in which the magnetization of the STO 65 is rotated simultaneously. By applying the high-frequency magnetic field generated by the simultaneous rotation to the magnetic recording layer 103, an increase in the recording track density can be achieved.

[0069] On the other hand, the magnetic flux control layer (STO) 65 generates heat by being energized. As a result, the magnetic material of the magnetic flux control layer 65 oxidizes, and oxides precipitate, causing the ABS 13 and the protective layer 68 near the magnetic flux control layer 65 to deform. Figure 5 FIG. is a cross-sectional view of a magnetic head schematically showing the deformation of the ABS 13 and the protective layer 68. As shown in the figure, at the tip of the recording head 58, an iron oxide layer 91 in which magnetic elements contained in the magnetic flux control layer 65 precipitate into the protective layer 68 due to, for example, iron oxidation pushes up the surface area 68a of the protective layer 68 and deforms it.

[0070] Thus, in the HDD of the present embodiment, contrary to the auxiliary effect of increasing the recording magnetic field obtained by energizing the magnetic flux control layer 65, oxides of the magnetic elements of the magnetic flux control layer 65 precipitate near the ABS, causing the ABS 13 and the protective layer 68 to deform. As a result, the distance between the disk and the tip of the recording head 58 becomes shorter, increasing the possibility of the recording head 58 contacting the disk and damaging it, and increasing the possibility of wear of the protective layer 68. In addition, due to the precipitation of oxides, the energization resistance of the magnetic flux control layer 65 increases.

[0071] Then, the HDD 10 of the present embodiment is configured to control the tilt (head skew) of the magnetic head, particularly the floating amount of the recording head, according to the deterioration of the magnetic head 16, for example, according to a decrease in the error rate of the magnetic head or an increase in the resistance value of the magnetic flux control layer 65, thereby suppressing the deterioration of the magnetic head. Hereinafter, the operation of controlling the tilt of the magnetic head will be described.

[0072] As shown Figure 3 in the figure, the MPU 46 of the main controller 40 includes: a resistance measurement unit 46a that measures the resistance value of the magnetic flux control layer (STO) 65; a first arithmetic unit 46b that calculates the percentage of the measured resistance value with respect to the initial resistance value of the STO 65 as the resistance value change rate, and the initial resistance value of the STO 65 is measured at the initial use of the magnetic head 16 and stored in the memory 47 as the initial value data 47b; an error rate measurement unit 46c that measures the error rate of the data written by the magnetic head 16; a second arithmetic unit 46d that calculates the change amount of the measured error rate with respect to the initial value of the error rate, and the initial value of the error rate is stored in the memory 47 as the initial value data 47b; a determination unit 46e that determines the recording tilt of the magnetic head 16 corresponding to the resistance value change rate and the error rate change amount; a tilt control unit 46f that controls the floating height of the magnetic head and the floating height of the recording head 58 according to the recording tilt information; and a heater power control unit 46g that, under the control of the tilt control unit 46f, adjusts the power ratio supplied to the first and second thermal actuators based on the heater power setting table 47a stored in the memory 47. The heater power setting table 47a records data in which the relationship between the tilt of the magnetic head (the floating height of the recording head 58) and the power ratio is tabulated.

[0073] Figure 6 is a flowchart showing the processing operation of controlling the tilt of the magnetic head 16 by the main controller 40.

[0074] As shown Figure 1 and Figure 6 in the figure, before performing the recording operation, the main controller 40 applies a predetermined recording current and STO current (ST1) to the magnetic head 16. Then, the error rate measurement unit 46c measures the error rate of the magnetic head 16 (ST2). The error rate arithmetic unit 46d obtains the error rate at the initial use of the magnetic head stored in the memory 47 and calculates the increase value of the measured error rate with respect to the initial error rate (ST3). The determination unit 46e determines whether the increase value of the error rate is a predetermined value, for example, +0.05 dB or more (ST4).

[0075] When it is +0.05 dB or more, the resistance measurement unit 46a measures the resistance value of the magnetic flux control layer (STO) 65 (ST5). The resistance arithmetic unit 46b obtains the initial resistance value of the magnetic flux control layer 65 at the initial use of the magnetic head in the initial value data 47b stored in the memory 47, and calculates the resistance value change rate as the ratio of the measured resistance value to the initial resistance value (ST6).

[0076] The determination unit 46e determines whether the error rate increase value and the resistance value change rate satisfy any one of the following relational expressions (1) and (2) (ST7).

[0077] The change rate of the resistance value ≤ 2%; the increase rate of the error rate > 0.05…(1)

[0078] The change rate of the resistance value > 2%; the increase rate of the error rate > (the change rate of the resistance value - 2) × 0.033…(2)

[0079] When satisfied, that is, when the increase rate of the error rate reaches the predetermined increase value before the change rate of the resistance value reaches the predetermined change rate, the determination unit 46f determines that the deterioration of the recording head has occurred. Thus, the determination unit 46f calculates the inclination of the head (the head tilt or the floating amount of the recording head) that prevents the magnetic head 16 from colliding with the magnetic disk 12. In the present embodiment, the inclination of the magnetic head is calculated so that the main magnetic pole 60 of the recording head 58 does not become the lowest point of the ABS (the point closest to the surface of the magnetic disk). Further, the determination unit 46e determines the heater power ratio (power ratio) corresponding to the calculated inclination based on the heater power setting table 47a stored in the memory 47 (ST8).

[0080] The heater power control unit 46g controls the power ratio of the power supplied to the first heater 76a and the second heater 76b according to the power ratio information from the determination unit 46f (ST9). After adjusting the inclination of the magnetic head 16, the recording head 58 of the magnetic head 16 performs the desired magnetic recording (ST10).

[0081] When the increase rate of the error rate in the above-described processing step (ST4) is smaller than the predetermined value, and when neither of the relational expressions (1) and (2) is satisfied in the processing step (ST7), the MPU 46 determines that the deterioration of the recording head 58 has not progressed, and performs the desired magnetic recording performed by the recording head 58.

[0082] The above-described magnetic head deterioration detection and deterioration suppression processing are performed for each magnetic recording of the recording head 58.

[0083] According to the HDD 10 of the first embodiment configured as described above, the deterioration state of the magnetic head is detected for each magnetic recording operation. In the case of deterioration, further deterioration of the magnetic head is suppressed by changing the head tilt of the magnetic head and the floating amount of the recording head. Thus, a magnetic disk device capable of suppressing the deterioration of the magnetic head and improving the reliability can be provided.

[0084] Next, the magnetic head of the HDD of other embodiments will be described. In the other embodiments described below, the same parts as those in the first embodiment are given the same reference numerals as in the first embodiment, and the detailed description thereof may be omitted or simplified sometimes.

[0085] (Second Embodiment)

[0086] Figure 7It is a side view schematically showing the head of the HDD according to the second embodiment.

[0087] As shown in the figure, according to the second embodiment, the head 16 has a third heater (third thermal actuator) 76c as a thermal actuator in addition to the first heater 76a and the second heater 76b. The third heater 76c is disposed on the side opposite to the second heater 76b with respect to the first heater 76a. The third heater 76c is disposed inside the slider 15 on the outer side of the first heater 76a, that is, on the trailing end 15b side.

[0088] When the main controller 40 detects the deterioration of the head 16, it increases the protrusion amount of the part on the trailing end side of the main magnetic pole 60 by applying power to the third heater 76c. Thereby, the head tilt of the head 16 is changed, and a new lowest point is formed on the trailing end side of the main magnetic pole 60, so that the main magnetic pole 60 can be protected, that is, the contact between the main magnetic pole 60 and the disk 12 can be prevented. In addition, the main controller 40 calculates and adjusts the heater power so that the floating height of the lowest point (= the height difference from the main magnetic pole) does not exceed 0.8 nm.

[0089] (Third Embodiment)

[0090] Figure 8 It is a side view schematically showing the head of the HDD according to the third embodiment.

[0091] As shown in the figure, according to the third embodiment, the head 16 has a cooling element (Peltier element, thermionic emission cooling substrate, etc.) 80 disposed between the first heater 76a and the second heater 76b as a thermal actuator. When the main controller 40 detects the deterioration of the recording head 58, it supplies power to the cooling element 80, and cools the area between the recording head 58 and the reproducing head 55 through the cooling element 80. The cooled area is lifted in the direction away from the disk 12. Thereby, the main magnetic pole 60 can be lifted and the lowest point of the ABS 13 can be moved toward the trailing shield 62 side. That is, the head tilt of the head 16 can be changed to prevent the contact between the main magnetic pole 60 and the disk 12.

[0092] (Fourth Embodiment)

[0093] Figure 9 It is a side view schematically showing the head of the HDD according to the fourth embodiment.

[0094] As shown in the figure, according to the fourth embodiment, the head 16 uses a thermally assisted element with a thermally assisted function as the auxiliary element. The head 16 includes: a laser oscillator (laser diode) 82 embedded in the head; a near-field light generating element (NFT element) 84 that is embedded in the head and exposed to the ABS 13 on the leading side of the main pole 60; and a waveguide LG embedded in the head that guides the laser emitted from the laser diode 82 to the NFT element 84. The laser diode 82 is electrically connected to the laser drive current supply circuit of the head amplifier IC 30 via wiring and a flexure (not shown).

[0095] The resistance measurement unit 46a of the main controller 40 described above is electrically connected to the near-field light generating element 84 and can measure the resistance value of the near-field light generating element 84. In addition, the STO current supply circuit 31 of the head amplifier IC 30 is replaced with a laser drive current supply circuit that supplies drive current to the laser diode 82.

[0096] The other configuration of the head 16 is the same as that of the head 16 in the first embodiment described above.

[0097] If drive current is supplied from the laser drive current supply circuit of the head amplifier IC 30 to the laser diode 82, the laser diode 82 oscillates laser light, which is supplied to the NFT element 84 via the waveguide LG, and near-field light is generated from the NFT element 84. The generated near-field light is applied to the disk 12 as thermal energy to locally heat the magnetic recording layer 103, thereby reducing the coercivity of the recording layer portion. A recording magnetic field from the main pole 60 is applied to the coercivity reduction region to write a signal. In this way, by writing a signal to a region where the coercivity is sufficiently reduced by locally heating a part of the magnetic recording layer 103, high-density recording can be performed.

[0098] In addition, in the fourth embodiment, any one of the first embodiment, the second embodiment, and the third embodiment can be applied to the control of the head tilt when the head 16 deteriorates.

[0099] (Fifth Embodiment)

[0100] Figure 10 is a side view schematically showing the head of the HDD according to the fifth embodiment, Figure 11 is a cross-sectional view showing an enlarged view of the tip of the recording head in the fifth embodiment.

[0101] As shown in the figure, according to the fifth embodiment, the head 16 uses an energy-assisted element as the auxiliary element. As Figure 11As shown, the recording head 58 has a nonmagnetic conductor 66 disposed in the write gap WG between the tip 60a of the main magnetic pole 60 and the trailing shield 62. The nonmagnetic conductor 66 is, for example, a single-layer nonmagnetic conductive layer formed of Cu, and is disposed in the write gap WG in a state where one surface abuts against the shield-side end face 60c of the main magnetic pole 60a and the other surface abuts against the top face 62b of the trailing shield 62. The top face of the nonmagnetic conductor 66 is exposed to the ABS 13.

[0102] The main magnetic pole 60 and the trailing shield 62 are electrically connected to the current supply circuit 71 via wiring. In one example, instead of the STO current supply circuit 31, the current supply circuit 71 is provided in the head amplifier IC 30. Current can be supplied in series from the current supply circuit 71 through the trailing shield 62, the nonmagnetic conductor 66, and the main magnetic pole 60. The current can also be supplied in the reverse direction, that is, through the main magnetic pole 60, the nonmagnetic conductor 66, and the trailing shield 62.

[0103] If a direct current is passed through the nonmagnetic conductor 66 in a state where a recording magnetic field is applied to the main magnetic pole 60, a circular magnetic field is generated in a direction transverse to the direction of the current flow. Due to the generated circular magnetic field, a magnetic field component in the transverse direction is generated in the magnetic flux of the recording magnetic field, assisting the magnetization switching of the main magnetic pole 60. That is, magnetization switching can be accelerated and jitter can be reduced, thus contributing to an increase in magnetic recording density.

[0104] In the fifth embodiment, the other configuration of the magnetic head 16 is the same as that of the magnetic head 16 in the first embodiment described above. In the fifth embodiment, any one of the first embodiment, the second embodiment, and the third embodiment described above can be applied to the control of the head tilt when the magnetic head 16 deteriorates.

[0105] Next, an example of an HDD will be described.

[0106] (Example 1)

[0107] The magnetic head 16 used in the first embodiment is fabricated as follows.

[0108] First, using DC magnetron sputtering, layers having the following materials and thicknesses are sequentially stacked on a main magnetic pole mainly composed of FeCo in the order of the first conductive layer, the adjustment layer, and the second conductive layer, thereby obtaining the magnetic flux control layer 65. As the materials of the first conductive layer, the adjustment layer, and the second conductive layer, the same materials as Figure 4 the intermediate layer 65a, the adjustment layer 65b, and the conduction cover layer 65c are used.

[0109] A mask layer for defining the dimensions in the strip height direction of the flux control layer 65 is formed, and then the flux control layer is etched by an ion beam etching (IBE) method until the main pole is exposed. SiOx of an insulating film is formed on the peripheral portion of the flux control layer 65, and then the mask layer is removed. In addition, a mask layer for defining the dimensions in the track width direction of the flux control layer 65 is formed, and etching is performed in the same manner. SiOx of an insulating film is formed on the peripheral portion of the flux control layer 65, thereby processing the flux control layer.

[0110] Next, NiFe is formed as a tail shield on the conduction cover layer 65c.

[0111] Then, on the main pole, flux control layer, tail shield, and insulating film on the ABS side, an Si base layer is formed to be approximately 1 nm by sputtering, and then diamond-like carbon is formed on the Si base layer by CVD method to form a protective layer with a thickness of 1.6 nm, thereby obtaining a magnetic head. Similarly, a total of 200 magnetic heads having a 1.6 nm protective layer on the ABS side are manufactured. The manufactured magnetic heads are set to manufacture an HDD.

[0112] As a long-term power-on test, the obtained HDD is powered on for 5000 hours at an ambient temperature of 80 °C with an applied voltage of 300 mV to the flux control layer 65. The resistance values of the flux control layer 65 before and after the power-on test are measured by the main controller of the HDD and compared. Among the 200 magnetic heads, for 100 magnetic heads, tilt control is not performed even when a bit error rate degradation is detected, while for the remaining 100 magnetic heads, the same tilt control as in the first embodiment described above is performed.

[0113] As a result, there are multiple magnetic heads in which the bit error rate has deteriorated at the time of 5000 hours with respect to the bit error rate value before the power-on test.

[0114] Using a critical value of -1.7 dB, an OK (qualified) / NG (unqualified) determination is made for the bit error rate value, and the number of units is counted, resulting in the following Table 1. In the HDD without tilt control, 35 out of 100 magnetic heads have a BER of NG, while in contrast, in the HDD with tilt control, only 5 out of 100 magnetic heads have a BER of NG. From this result, it can be said that in the HDD with tilt control, the number of magnetic heads with a bit error rate (BER) of NG can be significantly suppressed, and the deterioration of the main pole can be suppressed.

[0115]

Table 1

[0116] Tilt control BER NG Yes 5 / 100 No 35 / 100

[0117] (Example 2)

[0118] The head 16 used in the fourth embodiment is fabricated in the same manner as in Example 1. However, near the main pole 60, a waveguide LG for near-field light made of Al2O3 or Ta2O5 with a high refractive index is formed and connected to the laser diode 82 included in the light source unit. Instead of the flux control layer, a plasmon generation element is formed on the leading side of the main pole 60 and connected to the waveguide LG. Moreover, a heat dissipation layer made of Cu is formed near the main pole, and a head with a thermal assist function is fabricated. As the magnetic recording medium, a medium composed of a high-Hk material mainly containing FePt is used.

[0119] Fifty of the above-described heads were prepared, and 25 of them were used for evaluation under the same conditions as in Example 1. However, the evaluation ambient temperature was room temperature, and the evaluation time was 2000 hours. The evaluation results are shown in Table 2 below. Similarly to Example 2, it can also be said that in an HDD with tilt control, the number of cases where the bit error rate (BER) is NG can be significantly suppressed, and the deterioration of the main pole can be suppressed.

[0120]

Table 2

[0121] Tilt control BER NG Yes 5 / 25 No 10 / 25

[0122] (Example 3)

[0123] The head used in the fifth embodiment is fabricated in the same manner as in Example 1. However, instead of the flux control layer, Cu, which is a non-magnetic conductor, is buried between the main pole and the trailing shield with the same film thickness. In the head using this non-magnetic conductor, the magnetization reversal / rotation is not achieved by using the flux control layer, but by using the magnetic field generated by the current to assist the magnetization switching of the head. Two hundred of these heads were prepared, and 100 of them were used for evaluation under the same conditions as in Example 1. However, the evaluation ambient temperature was 70 °C, and the evaluation time was 5000 hours. The evaluation results are shown in Table 3 below. In the case of having tilt control, even when using the energy of the current to assist the head, the same effect of suppressing the BER to NG as in Examples 1 and 2 can be achieved.

[0124]

Table 3

[0125] Tilt control BER NG Yes 22 / 100 No 40 / 100

[0126] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the scope equivalent to the invention described in the claims.

[0127] The recording head of the magnetic head of the embodiment can also be applied to a recording head that does not have a leading shield and / or side shields. The materials, shapes, sizes, etc. of the elements of the head constituting the magnetic head can be changed as needed. In a disk device, the number of disks and the number of magnetic heads can be increased or decreased as needed, and various selections can also be made for the size of the disks.

Claims

1. A disk device having: A rotatable disk-shaped recording medium; A magnetic head having: A write head with a main magnetic pole for applying a recording magnetic field to the recording medium, an auxiliary element for assisting magnetic recording using the main magnetic pole, and a plurality of thermal actuators for controlling the head tilt with respect to the recording medium; and A controller having a detection unit for detecting deterioration of the magnetic head, and changing the head tilt of the magnetic head by the thermal actuator according to the detected deterioration, The controller controls the head tilt to increase the distance between the main magnetic pole and the recording medium when detecting deterioration of the magnetic head, The detection unit includes a resistance measurement unit for measuring the resistance value of the auxiliary element; When the bit error rate measured before the resistance value of the measured auxiliary element exceeds a predetermined value exceeds a predetermined value, the controller detects deterioration near the main magnetic pole and changes the head tilt.

2. The disk device according to claim 1, The detection unit includes a bit error rate measurement unit for measuring the bit error rate of the write head, and the controller changes the head tilt when the measured bit error rate exceeds a predetermined value.

3. The disk device according to claim 1 or 2, The auxiliary element includes a high-frequency oscillator disposed adjacent to the main magnetic pole.

4. The disk device according to claim 1 or 2, The auxiliary element includes an energy auxiliary element made of a non-magnetic conductor disposed in contact with the main magnetic pole.

5. The disk device according to claim 1 or 2, The auxiliary element includes a thermal auxiliary element for applying heat energy to the recording medium.

6. A disk device having: A rotatable disk-shaped recording medium; A magnetic head having: A write head with a main magnetic pole for applying a recording magnetic field to the recording medium, an auxiliary element for assisting magnetic recording using the main magnetic pole, and a plurality of thermal actuators for controlling the head tilt with respect to the recording medium; and A controller having a detection unit for detecting deterioration of the magnetic head, and changing the head tilt of the magnetic head by the thermal actuator according to the detected deterioration, The plurality of thermal actuators include a first heater for controlling the protrusion amount of the write head, and a second heater disposed apart from the first heater; The controller adjusts the power ratio of the power supplied to the first heater and the second heater to control the head tilt when detecting deterioration of the magnetic head.

7. A disk device having: A rotatable disk-shaped recording medium; A magnetic head having: A write head with a main magnetic pole for applying a recording magnetic field to the recording medium, an auxiliary element for assisting magnetic recording using the main magnetic pole, and a plurality of thermal actuators for controlling the head tilt with respect to the recording medium; and A controller having a detection unit for detecting deterioration of the magnetic head, and changing the head tilt of the magnetic head by the thermal actuator according to the detected deterioration, The plurality of thermal actuators include a first heater that controls the protrusion amount of the write head, a second heater that is disposed apart from the first heater, and a third heater that is disposed on a side opposite to the second heater with respect to the first heater; When the controller detects deterioration of the magnetic head, the controller supplies power to the third heater to control the head tilt.

8. A disk device having: A rotatable disk-shaped recording medium; A magnetic head having: a write head having a main magnetic pole for applying a recording magnetic field to the recording medium, an auxiliary element for assisting magnetic recording using the main magnetic pole, and a plurality of thermal actuators for controlling the head tilt with respect to the recording medium; And A controller having a detection unit that detects deterioration of the magnetic head, and changing the head tilt of the magnetic head by the thermal actuator according to the detected deterioration. The plurality of thermal actuators include a first heater that controls the protrusion amount of the write head, a second heater that is disposed apart from the first heater, and a cooling element that is disposed near the main magnetic pole between the first heater and the second heater; The controller cools the peripheral portion through the cooling element according to the deterioration detected by the detection unit, and raises the peripheral portion in a direction away from the recording medium to control the head tilt.

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