Magnetic recording / reproducing apparatus and method of controlling the same

Abstract

To suppress the occurrence of errors at the time of recording or reproducing data by reducing the difference in level of a lubricant on the surface of a magnetic recording medium.SOLUTION: According to an embodiment, there is provided a method of controlling a heat assisted magnetic recording and reproducing device in which a heat assisted magnetic recording head including a main magnetic pole, a near field transducer that generates near field light, a waveguide that propagates light to the near field transducer, and a laser light source that supplies light to the waveguide, and a heat assisted magnetic recording medium including a lubricant layer on a recording surface facing the heat assisted magnetic recording head are mounted, the method including: And performing a smoothing process of a surface of the lubricant layer by operating the thermally assisted magnetic recording head.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a magnetic recording and reproducing apparatus and a control method thereof. [Background technology]

[0002] In thermally assisted magnetic recording, near-field light emitted from a near-field light output device mounted on the head is used to raise the temperature of the magnetic recording medium and perform recording. The temperature of the magnetic recording medium rises to near its Curie temperature, e.g., 400°C, affecting the operation of the lubricant layer on the surface of the magnetic recording medium. Specifically, the temperature of the lubricant layer rises in the data area, making the lubricant more mobile. In the servo area, where no recording is performed, the temperature of the lubricant layer drops, preventing the lubricant from moving. As a result, it has been found that a step of several angstroms may occur in the radial direction between the data area and the servo area of ​​the lubricant layer. Similar step differences of several angstroms may also occur in the cross-track direction, resembling ruts. These irregularities in the lubricant layer can cause signal quality degradation due to fluctuations in flying height and head malfunction due to smear. Deterioration in signal quality leads to a worsening bit error rate, and head malfunction can cause errors during recording. For this reason, there is a need to reduce the irregularities in the lubricant layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,199,067 [Patent Document 2] US Patent Application Publication No. 2017 / 0221511 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments of the present invention is to reduce the step of the lubricant on the surface of the magnetic recording medium, thereby suppressing the occurrence of errors during recording or data reproduction. [Means for solving the problem]

[0005] According to an embodiment, there is provided a method for controlling 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 laser 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: A method for controlling a thermally assisted magnetic recording and reproducing device is provided, which includes irradiating the thermally assisted magnetic recording medium with near-field light by setting a laser current value to a second laser current value lower than a first laser current value during writing, and operating the thermally assisted magnetic recording head to perform a smoothing process on the surface of the lubricant layer. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a block diagram illustrating a configuration of an example of a magnetic recording and reproducing device according to a first embodiment. [Figure 2] 1 is a partial exploded perspective view of a magnetic recording and reproducing device according to a first embodiment. [Figure 3] FIG. 2 is a side view showing a magnetic recording medium, a magnetic head, and a suspension. [Figure 4] 1 is a cross-sectional view of a portion of a magnetic recording and reproducing device according to a first embodiment. [Figure 5] FIG. 3 is a flowchart illustrating a control method for the magnetic recording and reproducing device according to the first embodiment. [Figure 6] FIG. 2 is a model diagram showing a part of a step in a lubricant layer. [Figure 7] FIG. 10 is a graph showing an example of non-uniformity of a lubricant layer. [Figure 8] FIG. 1 is a model diagram showing an example of a smoothing process for a lubricant layer. [Figure 9]FIG. 1 is a model diagram showing an example of a smoothing process for a lubricant layer. [Figure 10] FIG. 10 is a graph showing data SNR when Iop is changed. [Figure 11] FIG. 10 is a diagram schematically showing a pattern for performing smoothing processing per track. [Figure 12] FIG. 2 is a schematic diagram illustrating an example of a step in a lubricant layer between cross tracks. [Figure 13] 10A and 10B are diagrams illustrating an example of a smoothing process in the cross-track direction. [Figure 14] 10A and 10B are diagrams illustrating another example of the smoothing process in the cross-track direction. [Figure 15] FIG. 10 is a diagram schematically illustrating yet another example of smoothing processing in the cross-track direction. [Figure 16] 10A and 10B are diagrams showing patterns of laser current application and flying height control relative to the head movement direction. [Figure 17] 10A and 10B are diagrams showing patterns of laser current application and flying height control relative to the head movement direction. [Figure 18] 10A and 10B are diagrams showing patterns of laser current application and flying height control relative to the head movement direction. [Figure 19] FIG. 4 is a block diagram showing another example of an MPU that can be used in the magnetic recording and reproducing device according to the first embodiment. [Figure 20] 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

[0007] The method for controlling a thermally-assisted magnetic recording and reproducing device according to the first embodiment includes setting a second laser current value lower than the first laser current value during writing and smoothing the surface of the lubricant layer using a thermally-assisted magnetic recording head. The smoothing process is performed by operating the thermally-assisted magnetic recording head on the surface of the lubricant layer while irradiating near-field light at the second laser current value. The thermally-assisted magnetic recording and reproducing device used includes 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 laser light source that supplies light to the waveguide, and a thermally-assisted magnetic recording medium having a lubricant layer on the recording surface facing the thermally-assisted magnetic recording head.

[0008] The thermally-assisted magnetic recording and reproducing device according to the second embodiment includes a thermally-assisted magnetic recording head, a thermally-assisted magnetic recording medium having a lubricant layer on the recording surface facing the thermally-assisted magnetic recording head, a laser current control unit that controls a laser current applied to a laser light source, a head operation control unit that controls the operation of the thermally-assisted magnetic recording head, and a smoothing processing unit that applies a laser current to the laser light source at a second laser current value that is lower than a first laser current value during writing, and operates the thermally-assisted magnetic recording head while irradiating near-field light onto the thermally-assisted magnetic recording medium, thereby smoothing the surface of the lubricant layer. The thermally-assisted magnetic recording head used includes 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 laser light source that supplies light to the waveguide.

[0009] According to the control method for the thermally-assisted magnetic recording and reproducing device of the first embodiment and the thermally-assisted magnetic recording and reproducing device of the second embodiment, by operating the thermally-assisted magnetic recording head at the second laser current value to perform a smoothing process on the lubricant layer surface, it is possible to reduce the step in the lubricant layer on the surface of the magnetic recording medium and suppress the occurrence of errors during recording or data reproduction. Operating the thermally-assisted magnetic recording head includes, for example, performing a seek operation or a write operation on the head.

[0010] 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.

[0011] First, the configuration of an example of a disk drive used in the 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 recording and reproducing device of the perpendicular magnetic recording type incorporating 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. FIG. 2 is an exploded perspective view of a portion of the magnetic recording and reproducing device. FIG. 2 shows a magnetic recording and reproducing device 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.

[0012] The disk 1 is fixed to a spindle motor (SPM) 2 and mounted for rotational motion. A lubricant layer 25 is provided on the surface of the disk 1. The magnetic head 10 is mounted on an actuator 3 and configured to move in a radial direction on the disk 1. The actuator 3 is driven to rotate by a voice coil motor (VCM) 4. 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.

[0013] 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, 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.

[0014] 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 (preamp) 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 is the main control unit of the disk drive, and executes servo control necessary for controlling read / write operations and positioning the magnetic head 10. The MPU 14 also includes a laser current control unit 19-1 that can control the laser current applied to the laser light source 32 to a second laser current value that is lower than the first laser current value during writing, a head operation control unit 19-2 that can control the operation of the magnetic recording head 10, and a smoothing processing unit 19-3 that applies a laser current to the laser light source 32 at the second laser current value and operates the thermally assisted magnetic recording head 10 while irradiating the thermally assisted magnetic recording medium 1 with near-field light, thereby smoothing the surface of the lubricant layer 25. The memory 17 includes a buffer memory made up of a DRAM, a flash memory, etc. It may also include a system area region of a magnetic recording medium.

[0016] 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.

[0017] 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 a write head 10W and a magnetic disk 1, which are part of a magnetic recording and reproducing device. The magnetic disk 1 has a substrate 20, a heat sink layer 21, a crystalline orientation layer 22, a perpendicular recording layer 23, and a protective film 24 coated with a lubricant 25 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 film 24 is disposed on top of the perpendicular recording layer 23 to protect it.

[0018] The magnetic head 10 is a separated 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 recording medium 1, and a waveguide 31 for propagating the light for generating near-field light. The light source is a laser diode 32 mounted on the slider of the actuator assembly 3. 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 recording and reproducing 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 is a flow diagram showing a control method for the magnetic recording and reproducing device according to the first embodiment. 5, in the control method for the magnetic recording and reproducing device according to the first embodiment, the smoothing processing unit 19-3 performs smoothing processing at the required timing. First, the smoothing processing unit 19-3 determines whether to perform smoothing processing (ST1). If smoothing processing is to be performed, the smoothing processing unit 19-3 sets the laser current value to a second laser current value lower than the first laser current value during writing in accordance with the laser current control unit 19-1 (ST2). Next, while irradiating near-field light at the second laser current value, the thermally assisted magnetic recording head is moved to the area where smoothing processing is to be performed in accordance with the head control unit 19-2, thereby smoothing the surface of the lubricant layer (ST3). If smoothing processing is not to be performed, the process waits for a certain period of time (ST2) and returns to the determination in ST1. This smoothing treatment is carried out to eliminate unevenness such as steps that occur on the surface of the lubricant layer.

[0021] FIG. 6 shows a model diagram showing part of the step in the lubricant layer. FIG. 7 is a graph showing an example of the non-uniformity of the lubricant layer. As shown in FIG. 6, when writing is performed in the downtrack direction indicated by arrow D with a first laser current value, the lubricant becomes more mobile in the region 10a heated by irradiation with near-field light, causing a step 25-1 to form on the surface of the lubricant layer 25. In the data region, this step 25-1 moves in accordance with the movement of the head indicated by arrow D. In contrast, in the servo region, where no recording is performed, the lubricant that is no longer heated solidifies, causing a step 25-2. In thermally assisted magnetic recording, due to such lubricant step 25-2, unevenness such as irregularities and the like as represented by curve 101 occurs on the lubricant layer surface from the servo region to the data region, as shown in FIG. 7. The difference in the height of the irregularities is approximately 1 to 10 angstroms, and such unevenness on the lubricant layer surface tends to cause deterioration of signal quality due to fluctuations in flying height and head malfunction due to smear.

[0022] 8 and 9 show model diagrams illustrating an example of a smoothing process for the lubricant layer. In the lubricant layer smoothing process, as shown in FIG. 8, the flying height of the thermally-assisted magnetic recording head 10 is set to the write height, the laser current value is set to a second laser current value lower than the first laser current value during write, and near-field light is applied to the area where a step 25-2 is expected to occur. While heating the lubricant layer in the area 10a, the thermally-assisted magnetic recording head 10 is operated in the track direction indicated by arrow D. Here, the expected area is the boundary between the data area and the servo area. The boundary between the data area and the servo area can include, for example, a distance equivalent to 1 bit from the boundary between the data area and the servo area to the servo area. Other areas include, for example, an area including the servo area and an area including the servo area and its 20% length before and after it. As shown in FIG. 9, the smoothing process smooths out the step 25-2 in the heated area 10a.

[0023] In this embodiment, during the smoothing process, the laser current value is set to a second laser current value that is lower than the first laser current value during writing. The laser current value is usually controlled by the preamplifier current value setting. The energy given to the laser diode (LD) is defined by the following equation (1). I total =I th (or I B )+I eff (or I op )…(1) In the formula, I total is the total current of the preamplifier, I th is the threshold current, I B is the bias current, I eff is the effective current, I op indicates the operating current.

[0024] I th Up to I th Exceeding I eff Near-field light is generated at the I position, heating the magnetic recording layer. th varies depending on the temperature and individual differences, so in magnetic recording and playback devices, I th I B is held as a parameter of the device, and I eff Equivalent to I total -I B =I op As I op By changing the value, the laser current can be controlled. Steps in the lubricant layer can occur in the down-track direction and the cross-track direction (radial direction) of the magnetic recording medium. The control method for the magnetic recording and reproducing device according to the embodiment can be used to smooth out steps in either direction.

[0025] As shown in FIGS. 8 and 9, a step in the lubricant layer in the down-track direction may occur, for example, between the servo and data sections. To smooth the step in the lubricant layer in the down-track direction, the head flying height is set to approximately the height used during writing and operated over an area where lubricant unevenness is expected. Near-field light is then irradiated to heat at least the lubricant in the convex lubricant areas. However, using the same laser current value as during writing may erase previously recorded data or servo patterns. Therefore, in the control method for a thermally assisted magnetic recording / reproducing device according to the embodiment, the laser current value is set to a second laser current value lower than the first laser current value used during writing, and near-field light is irradiated. The second laser current value can be 80% or less of the first laser current value. Furthermore, the second laser current value can be equal to or greater than the threshold current Ith.

[0026] Figure 10 shows the I op 10 shows a graph illustrating the data SNR when the value of is changed. In the figure, 102 is I op and SNR. Here, I op 100% is the I adjusted to maximize the ADC op is set as the standard value and is set as 100%. op When the SNR is below 80%, a sufficient decrease in SNR is observed, and it can be seen that the servo quality can be operated without any problems. op It can be seen that if the value is reduced to 70% or less, the impact can be further reduced.

[0027] FIG. 11 is a diagram showing a schematic representation of a pattern for performing smoothing processing per track. The area where the smoothing process is performed per track can include at least the servo area where the lubricant is convex. For example, pattern 1 shown in 103-1 indicates a position where smoothing is performed only in the servo area. Pattern 2 shown in 103-2 indicates a position where smoothing is performed slightly beyond the servo area. It is also effective to perform smoothing at a position on either side of the servo / data boundary where the lubricant unevenness varies, such as pattern 3 shown in 103-3, which is located upstream of the servo / data boundary in the head movement direction. Furthermore, it is also effective to perform smoothing at a position on either side of the servo / data boundary where the lubricant unevenness varies downstream of the head movement direction, such as pattern 4 shown in 103-4. Furthermore, it is possible to perform smoothing continuously over the entire area of ​​one track, such as pattern 5 shown in 103-5.

[0028] On the other hand, the step of the lubricant layer in the cross-track direction can be formed on both sides of the track, for example, and the smoothing treatment of the lubricant layer in the cross-track direction can be performed in the data area. FIG. 12 is a schematic diagram showing an example of a step in the lubricant layer between cross tracks. 12, for example, when the same track is written to multiple times in a short period of time using the thermally assisted magnetic recording head 10, the lubricant becomes more mobile in the region 10b of the written track that is heated by irradiation with near-field light and moves in the cross-track direction indicated by arrow F, which may cause a step 25-3 in the lubricant along the track and create a depression in the track. In this case, a smoothing process can be performed around the area including the step 25-3 that has become a convex.

[0029] To smooth the lubricant layer, the head's flying height is set to approximately the same as that used during writing, and the head is operated over an area where lubricant unevenness is expected. At this time, near-field light is irradiated onto at least the lubricant-protruding areas, thereby warming the lubricant. However, using the same laser current value as during writing can result in the erasure of previously recorded data and servo patterns. Therefore, in the control method for a thermally assisted magnetic recording / reproducing device according to the embodiment, the laser current value is set to a second laser current value lower than the first laser current value used during writing, and near-field light is irradiated. The second laser current value can be set to 80% or less of the first laser current value.

[0030] FIG. 13 is a diagram showing a schematic diagram of an example of smoothing processing in the cross-track direction. FIG. 14 is a diagram showing a schematic diagram of another example of the smoothing process in the cross-track direction. FIG. 15 is a diagram showing a schematic diagram of still another example of the smoothing process in the cross-track direction. In the figure, track 135 indicates a track where the lubricant layer has migrated in the cross-track direction, forming a depression. Tracks 134 on either side of track 135 are tracks where a protrusion has been formed by the lubricant layer that has migrated from track 135, and track 133 indicates a track in a standard state.

[0031] Cross-track smoothing 1 In the process of eliminating the step between cross tracks, for example, as shown in Fig. 13, a smoothing process can be performed by setting the laser current value to a second laser current value lower than the first laser current value during writing and irradiating near-field light on a track where lubricant has become convex (adjacent concave track) while moving the head to trace the track, as shown in Fig. 13. In this case, the smoothing process can be performed with the center position of the near-field light element within the track.

[0032] Cross-track smoothing 2 14, an offset function can be applied to the center position of track 135 and the write setting of track 135 to cover the most convex portion, gradually changing the offset value of adjacent track 135, and performing the process from the outside to the inside in the processing patterns shown in 130-1, 130-2, 130-3, and 130-4. Similarly, the offset value of the other adjacent track 135 can be gradually changed, and the head can be moved to the adjacent track from the outside to the inside in the processing patterns shown in 130-8, 130-7, 130-6, and 130-5. In this case, the laser current value is set to a second laser current value lower than the first laser current value during writing, and near-field light is irradiated. In smoothing process 2, the smoothing process can be performed at the center position of the track and with the near-field light element offset to the side from the center position of the track.

[0033] Cross-track smoothing 3 15, a method of gradually changing the offset value by applying the write offset function to track 133 from one end to track 133 on the other end, including tracks 135 and 134 with irregularities, and operating the head in a processing pattern of adjacent tracks 131-1, 131-2, 131-3, 131-4, 131-5, 131-6, 131-7, 131-8, 131-9, and 131-10, to perform smoothing processing can also be used. In this case, the laser current value can be set to a second laser current value lower than the first laser current value during writing, and near-field light can be irradiated. Furthermore, in smoothing processing 3, the smoothing processing can be performed with the near-field light element offset to the side from the center position of the track. When steps occur simultaneously in the down-track direction and the cross-track direction, the smoothing process can be performed simultaneously.

[0034] The following patterns can be given for the position of laser current application and flying height control. 16, 17, and 18 show diagrams showing patterns of laser current application and flying height control (back-off) in the head movement direction. Figure 16 shows the simplest control method, op This shows the case where control and DFH (Dynamic flying height) control are performed simultaneously. op control, 108 represents the DFH control. Position P1 represents the start position of the servo area, and position P2 represents the end position of the servo area.

[0035] Figure 17 shows I op Control is applied first, then DFH control is applied, and after DFH control is finished, I op This indicates the end of the control. op DFH control, 110. Position P1a indicates the position where the laser is turned on before the servo area starts, and position P2a indicates the position where the laser is turned off after the servo area starts. This pattern minimizes the effect of head protrusion caused by applying laser current.

[0036] Figure 18 shows the DFH control first, followed by the I op Take control and I op This shows the case where DFH control is terminated after the control is terminated. op Position P1 represents the start position of the servo area, and position P2 represents the end position of the servo area. Position P3a represents the position where the back-off control value is changed before the start of the servo area. Position P4a represents the position where the back-off control value is changed after the end of the servo area. In this pattern, in areas with few irregularities in the lubricant layer, I op A physical smoothing process for the lubricant layer without applying heat, i.e., by bringing the head into contact with the surface of the lubricant layer to smooth out the irregularities and then heating only the areas with the most irregularities, can be carried out effectively.

[0037] The flying height can basically be set to the same as the flying height during normal writing. To complete the smoothing process in a shorter time, the flying height can be set lower than during normal writing. Also, to avoid damage to the head, a high flying height can be used, but if it is higher than 0.5 nm, the smoothing effect tends to be reduced. In actual operation, the health monitor function is used to record the cumulative write time for each zone, and smoothing processing is performed every time a certain amount of time has passed. Alternatively, smoothing processing is performed every time a certain amount of time has passed based on the actual operating time. For example, when the HDD is idle, smoothing processing is forcibly performed on the entire lubricant layer of the magnetic recording layer, and when data is being read / written, smoothing processing is performed in order of the time that has elapsed. This allows the operation to be changed according to the operating status of the HDD.

[0038] For example, the smoothing process can be performed on tracks or zones where the measured value of the elapsed write time or the operating time of the thermally-assisted magnetic recording and reproducing device exceeds a certain value. Furthermore, during recording and reproducing, the smoothing process can be performed preferentially on tracks or zones where the measured value of the elapsed write time or the operating time of the thermally-assisted magnetic recording and reproducing device is high. Furthermore, during idle, the smoothing process can be performed on all areas of the write surface of the thermally-assisted magnetic writing medium, and the measured value of the elapsed write time or the operating time of the thermally-assisted magnetic writing and reproducing device can be reset to zero. The measurement value of the elapsed write time and the drive time is output to the workload log and can be read at any time, or the measurement value of the elapsed write time or the drive time of the thermally assisted magnetic recording and reproducing device is written to the NAND memory and can be read at any time.

[0039] FIG. 19 is a block diagram showing another example of an MPU that can be used in the magnetic recording and reproducing device according to the first embodiment. FIG. 19 is applicable to the magnetic recording and reproducing apparatus of FIG. 1, and has the same configuration as FIG. 1 except that MPU 14-1 is used instead of MPU 14. The MPU 14-1 first includes a laser current control unit 19-1 that can control the laser current applied to the laser light source 32 to a second laser current value that is lower than the first laser current value during writing, a head operation control unit 19-2 that can control the head operation of the magnetic recording head 10, a flying height control unit 19-4 that changes the flying height of the magnetic recording head 10 from a first flying height to a second flying height that is different from the first flying height, a smoothing processing unit 19-3 that applies a laser current to the laser light source 32 at the second laser current value and performs a smoothing process on the surface of the lubricant layer 25 by operating the thermally assisted magnetic recording head 10 while irradiating near-field light onto the thermally assisted magnetic recording medium 1, and a control unit 19-4 that determines the timing of the smoothing process, and determines the flying height adjustment position and I op and a timing control section 19-5 for controlling the application position.

[0040] FIG. 20 is a flowchart showing another example of the control method for the magnetic recording and reproducing device according to the first embodiment. As shown in the figure, in another example of the control method for the magnetic recording and reproducing device according to the first embodiment, I op The pattern of the application position and the pattern of the flying height adjustment position are determined in advance and stored as device parameters. After the disk drive 200 starts running, the timing control unit 19-5 periodically, for example, once an hour, determines whether to perform smoothing processing depending on the time elapsed since the previous smoothing processing (ST11). If a reference time or more has not elapsed since the previous smoothing processing, the process waits temporarily (ST16) and then returns to the determination in ST11. If a reference time or more has elapsed, the smoothing processing unit 19-3 performs smoothing processing of the lubricant layer. First, based on information from the smoothing processing unit 19-3, the head operation control unit 19-2 moves the relevant head to the relevant zone or track (ST12). The laser current control unit 19-1 sets a second laser current value lower than the first laser current value and op (ST13), and the flying height control section 19-4 changes the flying height to a desired value (ST14). op The order of application (ST13) and flying height control (ST14) may be reversed. opWith the lubricant applied, the head operates on the corresponding zone or track to perform smoothing processing (ST15). At this time, the difference in the lubricant between the servo and data is eliminated. This operation can be performed multiple times as needed, or it can be performed consecutively on multiple tracks. Once smoothing of the lubricant is complete, I op The operation of OFF and DFH OFF is performed, and the counter for the elapsed time since the previous smoothing process is reset to 0.

[0041] For example, the smoothing process is performed by adjusting the flying height to the first flying height in the flying height control unit 19-4 (ST14), turning on the laser irradiation, and op After the thermally assisted magnetic recording head passes the servo area, the laser irradiation is turned off and I op The voltage application can be stopped and the flying height can be adjusted to a second flying height different from the first flying height. For example, the smoothing process is performed by turning on the laser irradiation. op The magnetic head is applied (ST13), and the flying height control unit 19-4 adjusts the flying height lower. After the thermally assisted magnetic recording head passes the servo area, the flying height control unit 19-4 adjusts the flying height higher and turns off the laser irradiation. [Example]

[0042] Forty HDDs equipped with HAMR heads and media were prepared. Twenty of these underwent lubricant layer smoothing treatment, while the remaining 20 were run for 1,000 hours without the treatment. For the 20 drives that underwent smoothing treatment, the accumulated write time was checked once per hour during the run, and the lubricant smoothing treatment was also performed.

[0043] The laser current value was set to a second laser current value that was 50% of the first laser current value during writing.

[0044] The pattern of the positions where the smoothing process is performed per track is pattern 2 in FIG.

[0045] The pattern of the laser current application and the position of the flying height control (back-off) was set to the pattern shown in FIG.

[0046] The bit error rate (BER) was measured before and after the test, and any device with an error rate exceeding 10 to the power of -1.8 was judged to be NG. The number of NG devices before the test was zero under both conditions. Table 1 below shows the average number of smoothing treatments and the number of NG devices after the test. Of the 20 HDD devices that underwent smoothing treatment, there were zero NG devices, but for the comparison HDD device that did not undergo smoothing treatment, there were two NG devices. After the evaluation, the devices were disassembled and the area around the head was observed with an AFM, and it was found that the lubricant had aggregated and hardened around the head, preventing the head from operating smoothly.

[0047] [Table 1]

[0048] Example 2 Eighty HDDs equipped with HAMR heads and media were prepared. For 60 of the drives, the operating mode was set to cross-track smoothing processes 1 to 3, as shown in Figures 13, 14, and 15. 20 drives were subjected to each process, while the remaining 20 drives were left unprocessed. During the run, the accumulated write time was checked once per hour, and lubricant smoothing was performed. The bit error rate (BER) was measured before and after the test, and devices with an error rate exceeding 10 to the power of -1.8 were judged to have failed. The number of NG units before the test was zero under both conditions. Table 2 shows the average number of smoothing treatments and the number of NG units after the test. For HDD devices that underwent smoothing treatment, the number of NG units was 0 to 1, while for the comparison HDD device that did not undergo smoothing treatment, the number of NG units was 2. After the evaluation, the NG units were disassembled and the area around the head was observed with an AFM, and it was found that the lubricant had aggregated and hardened around the head, preventing the head from operating smoothly.

[0049] [Table 2]

[0050] Example 3 We prepared 120 HDDs equipped with HAMR heads and media. 100 of these were set to perform cross-track smoothing process 3, as well as down-track smoothing processes 1 to 5, with 20 units each, in the operating mode. The remaining 20 HDDs were used for comparison, and ran for 1,000 hours without smoothing. For the HDDs that underwent smoothing, the accumulated write time was checked once per hour and lubricant smoothing was performed during operation. The bit error rate (BER) was measured before and after the test, and any device with an error rate exceeding 10 to the power of -1.8 was judged to have failed. The number of NG devices before the test was zero under both conditions. The average number of smoothing treatments and the number of NG devices after the test are shown in Table 3 below. For the HDD devices that underwent smoothing treatment, the number of NG devices was 0 to 1, while for the comparison HDD devices, the number of NG devices was 2. After the evaluation, the NG devices were disassembled and the area around the head was observed using AFM, and it was found that the lubricant had aggregated and hardened around the head, preventing the head from operating smoothly.

[0051] [Table 3]

[0052] 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]

[0053] 1...magnetic recording medium, 1a...recording surface, 10, 10W, 10R...thermally assisted magnetic recording head, 19-1...laser current control section, 19-2...head control section, 19-3...smoothing processing section, 25...lubricant layer, 30...near-field optical element, 31...waveguide, 32...laser light source, 40...main pole, 200...magnetic recording and reproducing device

Claims

1. A method for controlling 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 laser 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, A method for controlling a thermally assisted magnetic recording and reproducing device, comprising: setting a laser current value to a second laser current value lower than a first laser current value during writing, irradiating the near-field light onto the thermally assisted magnetic recording medium, and operating the thermally assisted magnetic recording head to perform a smoothing process on the surface of the lubricant layer.

2. The method according to claim 1 , wherein the smoothing process is performed in an area including at least a boundary between a servo area and a data area.

3. The method of claim 1 , wherein the smoothing process is performed on an area including at least a servo area.

4. 2. The method according to claim 1, wherein the smoothing process is performed on an area including a servo area and 20% of the length before and after the servo area.

5. The method according to claim 1 , wherein the smoothing process is performed over an entire area of ​​one track.

6. The method of claim 1 , wherein the smoothing process is performed in the data domain.

7. The method according to claim 1 , wherein the smoothing process is performed with the center position of the near-field optical element located within a track.

8. 2. The method according to claim 1, wherein the smoothing process is performed with the near-field optical element offset in a lateral direction from a center position of the track.

9. The second laser current value is the threshold current I ｔｈ The method according to claim 1, wherein

10. The operating current value I at the second laser current value ｏｐ is the operating current value I at the first laser current value during writing ｏｐ The method of claim 1, wherein the concentration is 80% or less.

11. The method according to claim 1 , wherein the smoothing process includes adjusting the flying height of the thermally-assisted magnetic recording head to a flying height lower than that during writing.

12. The smoothing process is adjusting the flying height to a first flying height; Turn on the laser irradiation After the thermally assisted magnetic recording head passes through the servo area, the laser irradiation is turned off. The method of claim 1 , further comprising adjusting the flying height to a second flying height different from the first flying height.

13. The smoothing process is Turn on the laser irradiation Adjust the flying height to a low level, After the thermally assisted magnetic recording head passes through the servo area, The flying height is adjusted to be high, 10. The method of claim 1, further comprising turning off the laser irradiation.

14. The smoothing process is 2. The method of claim 1, further comprising carrying out the method on a track or zone for which a measured value of the elapsed write time or the drive time of the thermally assisted magnetic recording and reproducing device is equal to or greater than a certain value.

15. The smoothing process is 2. The method of claim 1, wherein the method is performed on all areas of the recording surface of the thermally assisted magnetic recording medium during idle time, and the measured value of the elapsed write time or the operating time of the thermally assisted magnetic recording and reproducing device is reset to zero.

16. The smoothing process is 2. The method according to claim 1, further comprising the step of giving priority to tracks or zones having a higher measured value of elapsed time of writing or a longer measured value of operating time of the thermally assisted magnetic recording and reproducing device when recording or reproducing data.

17. The method according to claim 1 , wherein the measured value of the elapsed time of writing or the operating time of the thermally assisted magnetic recording and reproducing device is output to a workload log and is read as needed.

18. 2. The method according to claim 1, wherein the measured value of the elapsed time of writing or the operating time of the thermally assisted magnetic recording and reproducing device is recorded in a NAND memory and read out as needed.

19. 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 laser light source that supplies light to the waveguide; a thermally assisted magnetic recording medium having a lubricant layer on a recording surface facing the thermally assisted magnetic recording head; a laser current control unit that controls a laser current applied to the laser light source; a head operation control unit that controls the operation of the thermally assisted magnetic recording head; a smoothing processing unit that applies a laser current to the laser light source at a second laser current value that is lower than a first laser current value during writing, and smooths the surface of the lubricant layer by operating the thermally assisted magnetic recording head while irradiating the near-field light onto the thermally assisted magnetic recording medium.

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