Thermally assisted magnetic recording / reproducing device and adjustment method thereof

Abstract

To provide a thermally assisted magnetic recording / reproducing device in which a lubricant hardened material is provided in advance near a near field optical element in a head while minimizing impact on areas other than an area where a lubricant hardened material is formed, and an adjustment method thereof.SOLUTION: An adjustment method of a thermally assisted magnetic recording / reproducing device according to the embodiment includes: maintaining a thermally assisted magnetic recording head of the thermally assisted magnetic recording / reproducing device on-track; maintaining a record current for data recording for the thermally assisted magnetic recording head that is less than a threshold value; and applying a light source drive current for light emission to a light source.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a thermally assisted magnetic recording and reproducing device and a method for adjusting the same. [Background technology]

[0002] In thermally assisted magnetic recording heads, recording is performed by raising the temperature of the magnetic disk with a laser. During this process, it has been found that components thought to originate from the magnetic film of the magnetic disk adhere to the tip of the near-field optical element (NFT) via the lubricant, forming a hardened substance. The formation of hardened lubricant cannot be prevented due to the recording principle. However, when hardened lubricant adheres, it is known to increase the laser transmittance and act as a layer that increases the laser transmission efficiency.

[0003] The hardened lubricant is worn away by wear when the flying height is reduced, and is rebuilt when the flying height is increased by filling the gap between the head and the media. Therefore, when the flying height changes within the disk surface, for example, when the head moves from a track with low flying height to a track with high flying height, the problem of reduced write performance occurs until the hardened lubricant is generated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 9,922,676 [Patent Document 2] U.S. Patent No. 10,529,364 [Patent Document 3] Japanese Patent Application Publication No. 63-091815 Summary of the Invention [Problem to be solved by the invention]

[0005] The hardened lubricant is provided in advance near the near-field optical element of the head while minimizing the influence on areas other than the area where the hardened lubricant is to be formed. [Means for solving the problem]

[0006] According to an embodiment, there is provided a method for adjusting a thermally assisted magnetic recording and reproducing device equipped with a thermally assisted magnetic recording head including a main pole, a near-field light element that generates near-field light, a waveguide that propagates light to the near-field light element, and a light source that supplies light to the waveguide, and a thermally assisted magnetic recording medium that includes a lubricant layer on a recording surface facing the thermally assisted magnetic recording head, the method comprising: maintaining the thermally assisted magnetic recording head on-track; A method for adjusting a thermally assisted magnetic recording / reproducing device is provided, which includes maintaining a recording current for recording data in the thermally assisted magnetic recording head below a threshold value, applying a light source drive current for emitting light to the light source, and generating a hardened lubricant at the tip of the near-field light element. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 10 is a block diagram illustrating an example of the configuration of a magnetic recording and reproducing device according to a second embodiment. [Figure 2] 10 is a partial exploded perspective view of a magnetic recording and reproducing device according to a second embodiment. [Figure 3] FIG. 2 is a side view showing the magnetic head and the suspension. [Figure 4] FIG. 10 is a cross-sectional view of a portion of a magnetic recording and reproducing device according to a second embodiment. [Figure 5] FIG. 3 is a flowchart illustrating an example of a control method for the magnetic recording and reproducing device according to the first embodiment. [Figure 6] FIG. 2 is a model diagram illustrating a hardened lubricant. [Figure 7] 10A and 10B are diagrams illustrating examples of areas other than the data recording area. [Figure 8] FIG. 10 is a flowchart illustrating another example of the control method for the magnetic recording and reproducing device according to the first embodiment. [Figure 9]FIG. 10 is a flowchart illustrating another example of the control method for the magnetic recording and reproducing device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The method for adjusting a thermally-assisted magnetic recording and reproducing device according to the first embodiment includes maintaining the thermally-assisted magnetic recording head of the thermally-assisted magnetic recording and reproducing device on-track, maintaining a write current for recording data below a threshold value for the thermally-assisted magnetic recording head, and applying a light source drive current for emitting light to the light source. The thermally-assisted magnetic recording and reproducing device used includes a thermally-assisted magnetic recording head including a main pole, a near-field optical element that generates near-field light, a waveguide that propagates light to the near-field optical element, and a light source that supplies light to the waveguide, and a thermally-assisted magnetic recording medium disposed opposite the thermally-assisted magnetic recording head and having a lubricant layer provided on the recording surface facing the thermally-assisted magnetic recording head.

[0009] The thermally assisted magnetic recording and reproducing device of the second embodiment is an apparatus that can be used in the adjustment method of the first embodiment, and is equipped with a thermally assisted magnetic recording head having a main pole, a near-field light element that generates near-field light, a waveguide that propagates light to the near-field light element, and a light source that supplies light to the waveguide; a thermally assisted magnetic recording medium having a lubricant layer on the recording surface facing the thermally assisted magnetic recording head; a head position control unit that keeps the thermally assisted magnetic recording head on-track; a recording current control unit that controls the data recording current applied to the thermally assisted magnetic recording head; a light source drive current control unit that controls the light source drive current applied to the light source; and a lubricant hardened product generation processing unit that applies the light source drive current to the light source while controlling the data recording current to be less than a threshold value, and performs a process to generate a hardened lubricant product at the tip of the near-field light element.

[0010] According to the first and second embodiments, when forming the hardened lubricant, a thermally assisted magnetic recording head is used, and when a light source drive current is applied to the light source, the recording current for data recording is maintained below a threshold value. This allows the recording layer and lubricant layer near the near-field light element to be locally heated to form the hardened lubricant, while minimizing the impact on areas other than the area where the hardened lubricant is formed, making it possible to perform data recording or pattern formation without degrading recording and playback performance. Furthermore, by providing the hardened lubricant in advance, the time required for the lubricant to fill the gap between the NFT tip and the magnetic recording medium in an on-track state according to the head flying height, i.e., the time until recording performance deteriorates, can be shortened as much as possible.

[0011] Hereinafter, embodiments will be described 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 as appropriate.

[0012] Example Hereinafter, the embodiment will be described in detail with reference to examples. First, the configuration of an example of a disk drive according to the second embodiment will be described with reference to Fig. 1. The configuration of the disk drive, which is a magnetic recording and reproducing device, shown in Fig. 1 is also applied to each embodiment described later. As shown in FIG. 1, the disk drive 200 is a magnetic disk device of the perpendicular magnetic recording type that incorporates a magnetic disk 1, which is a perpendicular magnetic recording medium, and a magnetic head 10 having a magnetic flux control layer, which will be described later.

[0013] FIG. 2 is a partial exploded perspective view of the magnetic recording and reproducing device according to the second embodiment. FIG. 2 shows a magnetic recording and reproducing device according to the second embodiment, in which a plurality of magnetic disks 1 and a plurality of magnetic heads 10 are housed in a housing 51, with the cover omitted. The magnetic disk 1 is fixed to a spindle motor (SPM) 2 and mounted for rotational motion. The magnetic head 10 is mounted on an actuator 3 and configured to move radially above the magnetic disk 1. The actuator 3 is driven to rotate by a voice coil motor (VCM) 4. A columnar inner stopper 11b, made of, for example, a synthetic adsorbent, can be provided on the bottom wall 52a around the voice coil motor (VCM) 4. The inner stopper 11b can reduce the impact of the actuator 3 colliding with the VCM column when moving the head to the inner periphery of the magnetic disk 1. In FIG. 1, for example, the magnetic head 10 is shown seeking to an arbitrary position on the recording surface 1a, and the magnetic head 10' mounted on the actuator 3' is shown fixed by pressing against the inner stopper 11b. The magnetic head 10 includes a write head 10W, a read head 10R, and a thermal assist unit 100. The write head 10W writes data to the magnetic disk 1. The read head 10R reads data from the magnetic disk 1. The thermal assist unit 100 assists the write head 10W in writing data to the magnetic disk 1. The magnetic head 10 may include a single magnetic head or multiple magnetic heads.

[0014] Furthermore, the disk drive has a head amplifier integrated circuit (hereinafter referred to as head amplifier IC) 11, a read / write channel (R / W channel) 12, a hard disk controller (HDC) 13, a microprocessor (MPU) 14-1, a driver IC 16, and memory 17. The R / W channel 12, HDC 13, and MPU 14 are incorporated into a controller 15 consisting of a single integrated circuit chip. As will be described later, the head amplifier IC11 includes a group of circuits for driving a laser diode for thermal assist. Furthermore, the head amplifier IC11 includes a driver that supplies the recording head 10W with a recording signal (write current) corresponding to write data supplied from the R / W channel 12. The head amplifier IC11 also includes a read amplifier that amplifies the read signal output from the reproducing head 10R and transmits it to the R / W channel 12.

[0015] The R / W channel 12 is a signal processing circuit for read / write data. The HDC 13 constitutes an interface between the disk drive and the host 18, and controls the transfer of read / write data. The MPU 14-1 is the main control unit of the disk drive, and controls read / write operations and executes servo control necessary for positioning the magnetic head 10. The MPU 14-1 further includes a head position control unit 19 that maintains the thermally assisted magnetic recording head 10 on-track, a light source drive current control unit 71 that controls a light source drive current applied to the light source, a recording current control unit 72 that controls a data recording current applied to the thermally assisted magnetic recording head, and a lubricant cured product generation processing unit 73 that applies the light source drive current to the light source while controlling the data recording current to be less than a threshold value, and performs processing to generate a lubricant cured product at the tip of the near-field light element. The memory 17 includes a buffer memory made up of a DRAM, a flash memory, and the like. FIG. 3 is a side view showing the magnetic head 10 and the suspension. As shown in Fig. 3, each magnetic head 10 is configured as a floating-type head and includes a substantially rectangular parallelepiped slider 42 and a recording / reproducing head portion 44 provided at the trailing end of the slider 42. The magnetic head 10 is fixed to a gimbal spring 41 provided at the tip of a suspension 34. A head load L is applied to each magnetic head 10 toward the surface of the magnetic disk 1 due to the elasticity of the suspension 34. As shown in Fig. 2, each magnetic head 10 is connected to a head amplifier IC 11 and an HDC 13 via a wiring member (flexure) 35 fixed on the suspension 34 and an arm.

[0016] Next, the configurations of the magnetic disk 1 and the magnetic head 10 will be described in detail. FIG. 4 is a cross-sectional view of the write head 10W and the magnetic disk 1, which are part of the magnetic disk device. The magnetic disk 1 has a substrate 20, and a heat sink layer 21, a crystalline orientation layer 22, a perpendicular recording layer 23, and a protective layer 24 coated with a lubricant on its surface, which are stacked in this order on the substrate 20. The perpendicular recording layer 23 has large anisotropy in the direction perpendicular to the disk surface. The crystalline orientation layer 22 is disposed below the perpendicular recording layer 23 to improve the orientation of the perpendicular recording layer 23. The heat sink layer 21 is disposed below the crystalline orientation layer 22 to suppress the spread of the heated region. The protective layer 24 is disposed on top of the perpendicular recording layer 23 to protect it.

[0017] The magnetic head 10 is a separate magnetic head in which the recording head 10W and the reproducing head 10R are separated. The recording head 10W comprises a main pole 40 made of a high-permeability material that generates a magnetic field perpendicular to the disk surface, a trailing yoke 50 magnetically joined to the main pole that passes magnetic flux to the main pole 40, a return shield pole 60 disposed on the leading side of the main pole 40 to efficiently close the magnetic path directly below the main pole, a coil 70 disposed so as to wrap around the magnetic path including the trailing yoke and return shield pole to pass magnetic flux to the main pole 40, a heater 80 for controlling the flying height of the recording head, and a near-field optical element 30 disposed on the leading side of the main pole 40 that generates near-field light that heats the perpendicular recording layer 23 of the magnetic disk 1, and a waveguide 31 for propagating the light for generating near-field light. A laser diode is incorporated as a light source 32 by mounting it on the slider of the actuator assembly 3.

[0018] The write current applied to the coil 70 can be suppressed below a threshold value in accordance with write current information from the write current control unit 72 in Fig. 1. The light source drive current to the light source 32 can be applied based on light source drive current information from the light source drive current control unit 71 in Fig. 1. For example, Au, Pd, Pt, Rh, or Ir, or an alloy made of a combination of some of these, can be used for the near-field light element 30. For example, an oxide made of SiO2, Al2O3, or the like can be used for the insulating layer provided between the main pole and the near-field light element.

[0019] Recording methods for thermally assisted magnetic recording that can be used in the magnetic disk device 200 include a conventional recording method known as CMR (Conventional Magnetic Recording), in which tracks are written at radial intervals and recording is performed so that adjacent tracks do not overlap; a shingled recording method known as SMR (Shingled Magnetic Recording), in which tracks are stacked in order in the radial direction and recording is performed by overlapping part of an adjacent track; an interlaced recording method known as IMR (Interlaced Magnetic Recording), in which adjacent tracks are alternately stacked on a bottom track and a top track, and after recording on the bottom track, recording is performed on the interlaced top track by overlapping the bottom track; or a combination of these.

[0020] FIG. 5 shows an example of a flow diagram illustrating a control method for the magnetic recording and reproducing device according to the first embodiment. FIG. 6 shows a model diagram of the hardened lubricant formed on the thermally assisted magnetic recording head. 5, first, a thermally assisted magnetic recording head 10 having an NFT 30 and a main pole 40 at its tip is levitated and maintained in an on-track state (ST1) on a magnetic disk 1 having a magnetic recording layer 23, a protective layer 24, and a lubricant layer 25 applied to the protective layer 24, with the head flying height at a height H1. A lubricant is then filled into the gap between the tip of the NFT 30 and the lubricant layer 25 of the magnetic recording medium. Next, in accordance with the lubricant-hardened product generation processing information from a lubricant-hardened product generation processing unit 73, the recording current applied to the coil 70 is kept below a threshold (ST2), while a light source drive current is applied to the light source 32 (ST3). This is maintained for a certain period of time, thereby locally heating the recording layer and lubricant near the NFT 30 and generating a lubricant-hardened product (ST4).

[0021] This allows the lubricant filled at the tip of the NFT 30 from the lubricant layer 25 to harden, as shown in Figure 6, while minimizing the impact on areas other than the area where the hardened lubricant is formed, and allows a hardened lubricant 26 having a first height H1 to adhere to the thermally assisted magnetic recording head 10. The hardened lubricant can be produced before or after shipping of the thermally assisted magnetic recording / reproducing device, in the user's environment, or at a time other than when data is recorded, and can also be produced in any area other than the data recording area.

[0022] Areas other than the data recording area include, for example, servo recording areas, defect areas that avoid protrusions that may cause head deterioration, band areas for shingled magnetic recording (SMR), areas within the system area where writing may be performed, such as areas to check for head deterioration, areas that are reserved for some reason, and other areas that are reserved for SMR media cache or ATI (adjacent track interference) rewrites, which are specified to improve performance, or spare areas reserved for future defects.

[0023] FIG. 7 is a diagram illustrating an example of an area other than the data recording area, showing a model diagram representing a guard band as a band area of ​​shingled magnetic recording (SMR). As shown in the figure, a guard band 61-2 is provided between one shingled band 62-1 and an adjacent band 62-2, and band 62-1 is provided with shingled tracks N, N+1, N+2, N+3, N+4, and N+5. Guard band 61-2 is also provided with shingled tracks M, M+1, M+2, M+3, M+4, and M+5. Guard band 61-2 is spaced a short distance from tracks N+5 and M on either side of it, and is not shingled. Guard band 61-1 is provided on the opposite side of guard band 61-2 across shingled band 62-1, and guard band 61-3 is provided on the opposite side of guard band 61-2 across shingled band 62-2, and each is spaced a short distance from the tracks on either side, and is not shingled.

[0024] Examples of timings other than the timing for data recording include the timing before writing servo information such as self-servo write, when the idle state continues for a certain period of time or more, once every certain period of time, or in the background of data recording. Before shipping a thermally assisted magnetic recording and reproducing device, a hardened lubricant can be formed on the recording surface of the thermally assisted magnetic recording medium at a timing other than the timing at which data is recorded, such as before forming a reference servo pattern for servo writing, such as a concentric or spiral pattern. This prevents deterioration of read / write characteristics due to the hardened lubricant when forming the reference pattern thereafter. Furthermore, during subsequent servo writing, an on-track state for the reference servo pattern can be maintained without any problems.

[0025] The recording current is a current that can be used to record data, such as the current applied to the magnetic coil of a recording head when recording data. The threshold value of the recording current can be kept to a very low level that does not cause magnetization reversal in the magnetic recording layer of the magnetic recording medium. The threshold value of the recording current can be set to, for example, greater than 0 and equal to or less than 17 mA. 17When the current exceeds 100 mA, it tends to be a current value that causes magnetization reversal in the recording layer of the magnetic recording medium. The recording current can be set to 0, which is the OFF state. The light source driving current is a current that causes the light source to emit light. For example, a laser light source can be used as the light source. The time for which the light source drive current is applied to the light source 32 while the recording current is kept within the threshold value can be maintained for at least 4 milliseconds, and up to about 10 seconds.

[0026] Example 1 In the first embodiment, an example is shown in which a hardened lubricant is produced before forming a concentric or spiral servo write reference servo pattern on the recording surface. FIG. 8 shows another example of a flow chart illustrating the control method of the magnetic recording and reproducing device according to the first embodiment. First, the head 10 is floated over an area of ​​the recording surface where a reference servo pattern is to be formed (ST11). Before floating the head 10, it is possible to determine, if necessary, whether it is time to generate a hardened lubricant in an area other than the data area. Next, the recording head is fixed by pressing the inner stopper 11b, or another head of the multiple magnetic heads 10 facing another recording surface is brought on-track to the spiral pattern or servo pattern, thereby fixing the head used for recording and maintaining the on-track state (ST12). Next, while the recording current is turned off below a threshold (ST13), for example, the recording current is turned on (ST14), and the light source drive current for the recording head 10 is turned on for a certain period of time (ST15). The process is continued for 10 milliseconds to form a hardened lubricant near the NFT 31 of the recording head 10W (ST15). After that, a reference servo pattern for servo writing in a concentric or spiral shape is formed (ST16).

[0027] According to Example 1, as shown in ST13 and ST14, before forming a concentric or spiral servo write reference servo pattern, the recording current is lowered below a threshold value (for example, the recording current is turned off while the light source drive current for the recording head is turned on), thereby generating a hardened lubricant near the NFT of the recording head. This allows the hardened lubricant to be generated while minimizing the impact on areas other than the area where the reference servo pattern is formed. This minimizes the time required for the lubricant to fill the gap between the NFT tip and the magnetic recording medium in accordance with the head flying height, i.e., the time it takes for recording performance to deteriorate, and enables data recording or pattern formation, etc., without degrading the recording and playback performance in areas other than the area where the hardened lubricant is formed. Note that ST13 and ST14 can be performed simultaneously or in reverse order. On the other hand, if the recording current is not set below the threshold, it will have a negative effect on areas other than the area where the reference servo pattern is formed, making it difficult to maintain on-track when forming the reference servo pattern for spiral servo writing, and making it difficult to create the reference servo pattern.

[0028] Example 2 In Example 2, an example is shown in which a cured lubricant is produced in a user's environment after shipping. FIG. 9 shows yet another example of a flow chart illustrating the control method of the magnetic recording and reproducing device according to the first embodiment. The thermally assisted magnetic recording and reproducing device is placed in a user environment. First, it determines whether a certain period of time has elapsed without receiving a command from the host 18 (ST21). If the certain period of time has not elapsed, the process ends. If the certain period of time has elapsed, the recording head 10 is moved to, for example, a defect registration location or an SMR band position to maintain on-track (ST22). Note that a defect registration location refers to a location on the magnetic recording medium where data cannot be recorded. Among defect registration locations, protrusions can be avoided because they may cause head deterioration. While the recording current is turned off (ST23), for example, below a threshold, the light source drive current for the recording head 10 is turned on (ST24). This is maintained for a certain period of time, and a hardened lubricant is formed near the NFT 31 of the recording head 10W, and the process ends (ST25).

[0029] According to Example 2, as shown in ST23 and ST24, in a user environment, a recording current below a threshold is applied to the defect registration location or SMR band position (for example, by turning on the light source drive current for the recording head while turning off the recording current), thereby generating a cured lubricant near the NFT of the recording head. This allows the generation of a cured lubricant while minimizing the impact on areas other than the defect registration location or SMR band position. This shortens the time required for the lubricant to fill the gap between the NFT tip and the magnetic recording medium in an on-track state according to the head flying height, i.e., the time it takes for recording performance to deteriorate. This makes it possible to perform data recording or pattern formation without degrading the recording / reproducing performance in areas other than the area where the cured lubricant is formed. On the other hand, if the recording current is not set below the threshold, it will adversely affect the defect registration area or areas other than the SMR band position, which tends to make it difficult to maintain on-track during recording.

[0030] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0031] 1...thermally assisted magnetic recording medium, 1a...recording surface, 10...magnetic head, 10W...thermally assisted magnetic recording head, 14-1...MPU, 19...head position control unit, 25...lubricant layer, 30...near-field optical element, 31...waveguide, 32...light source, 40...main pole, 70...coil, 71...light source drive current control unit, 72...recording current control unit, 73...lubricant hardened product generation processing unit, 200...thermally assisted magnetic recording and reproducing device

Claims

1. 1. A method for adjusting a thermally assisted magnetic recording and reproducing device equipped with a thermally assisted magnetic recording head including a main pole, a near-field light element that generates near-field light, a waveguide that propagates light to the near-field light element, and a light source that supplies light to the waveguide, and a thermally assisted magnetic recording medium having a lubricant layer on a recording surface facing the thermally assisted magnetic recording head, comprising: maintaining the thermally assisted magnetic recording head on-track; A method for adjusting a thermally assisted magnetic recording / reproducing device, comprising: maintaining a recording current for recording data to the thermally assisted magnetic recording head below a threshold value; applying a light source drive current for emitting light to the light source; and generating a hardened lubricant at the tip of the near-field light element.

2. The method of claim 1 , wherein the threshold is greater than 0 and less than or equal to 17 mA.

3. The method of claim 1 , wherein the recording current is zero.

4. 2. The method according to claim 1, further comprising forming a concentric or spiral reference servo pattern for servowriting on the recording surface after forming the hardened lubricant.

5. The method of claim 1 , wherein the thermally assisted magnetic recording / reproducing device is adjusted in a user environment.

6. The method of claim 1 , wherein maintaining the thermally-assisted magnetic recording head on-track includes moving the thermally-assisted magnetic recording head to a defect registration location or a band position of an SMR.

7. a thermally assisted magnetic recording head including a main pole, a near-field light element that generates near-field light, a waveguide that propagates light to the near-field light element, and a light source that supplies light to the waveguide; a thermally assisted magnetic recording medium having a lubricant layer on a recording surface facing a thermally assisted magnetic recording head; a head position control unit that maintains the thermally assisted magnetic recording head on-track; a data recording current control unit that controls a data recording current applied to the thermally assisted magnetic recording head; a light source drive current control unit that controls a light source drive current applied to the light source; a lubricant hardening processing unit that applies the light source drive current to the light source while controlling the data recording current to be less than a threshold value, and performs a process to generate a lubricant hardening material at the tip of the near-field light element.

8. 8. The thermally assisted magnetic recording and reproducing device according to claim 7, wherein the threshold value is between 0 and 17 mA.

9. 8. The thermally assisted magnetic recording and reproducing apparatus according to claim 7, wherein the threshold value is zero.

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