Disk device

Abstract

The present disclosure provides a disk device that can maintain signal quality even when a mode jump occurs in the shingled recording mode. The disk device includes: a disk; a magnetic head having a write head, a thermal assist unit that uses a near-field light element to assist in writing data of the write head, and a read head; a monitoring unit that monitors the light output; and a control unit that controls reading of data and writing of data based on the shingled recording mode. When writing data to the first track, the control unit controls the position of the write head and rewrites the data to the second track that is one track ahead of the first track when the absolute difference between the light output monitored by the monitoring unit during writing and the light output monitored by the monitoring unit in the previous time exceeds a predetermined value.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2021-137227 (filing date: August 25, 2021). This application incorporates all the contents of the base application by reference thereto. Technical Field

[0002] The embodiment relates to a disk device. Background Art

[0003] There is known a disk device having a magnetic head that assists writing of data by a thermal assist unit. Such a disk device has a near-field light element in the magnetic head. The magnetic head irradiates light from a laser diode as a light source onto the near-field light element, and generates near-field light from the front end of the element, thereby locally heating a medium recording layer having high perpendicular magnetic anisotropy. For the heated recording layer portion, since the coercive force is sufficiently reduced during recording, high recording density becomes possible.

[0004] However, there are cases where the laser diode exhibits a phenomenon called mode hopping in which the oscillation wavelength changes due to environmental temperature, self-heating, etc. When this phenomenon occurs, even when driven with a constant laser current, the light output changes. If this mode hopping occurs during the process of writing data, the heating range of the medium recording layer changes due to the change in the light output. Thus, for example, when the heating range becomes larger, there is a concern of erasing information on adjacent tracks. Such a concern is more significant in the overwrite recording method of shingled recording. Summary of the Invention

[0005] An object of the embodiment is to provide a disk device that can maintain signal quality even when mode hopping occurs in the shingled recording method.

[0006] A disk device according to an embodiment includes: a disk; a magnetic head having a write head for writing data to the disk, a thermal assist unit for assisting writing of data of the write head using a near-field light element, and a read head for reading data from the disk; a monitoring unit for monitoring the light output; and a control unit for controlling reading of data from the disk by the magnetic head and writing of data to the disk based on the shingled recording method. When writing data to a first track, the control unit controls the position of the write head and rewrites the data to a second track that is one track ahead of the first track when the absolute difference between the light output monitored by the monitoring unit during writing and the light output monitored by the monitoring unit in the previous time exceeds a predetermined value. Brief Description of the Drawings

[0007] Figure 1 It is a block diagram showing an example of the control configuration of the disk device of the embodiment.

[0008] Figure 2 It is a diagram showing an example of a cross section of a write head portion of a magnetic head including a thermal assist portion and a magnetic disk in this embodiment.

[0009] Figure 3 It is a diagram for explaining the technology of a magnetic disk device.

[0010] Figure 4 It is a diagram for explaining the technology of a magnetic disk device.

[0011] Figure 5 It is a diagram for explaining the technology of a magnetic disk device.

[0012] Figure 6 It is a diagram for explaining the technology of a magnetic disk device.

[0013] Figure 7 It is a diagram for explaining the technology of a magnetic disk device.

[0014] Figure 8 It is a diagram for explaining the technology of a magnetic disk device.

[0015] Figure 9 It is a diagram showing an example of the distribution of the magnetic write width when data is written by driving with an arbitrary constant laser current in the technology of a magnetic disk device.

[0016] Figure 10 It is a flowchart showing an example of the process of storing the optical output and magnetic write width in this embodiment.

[0017] Figure 11 It is a flowchart showing an example of the process of recording one round on a target track in the user data area in this embodiment.

[0018] Figure 12 It is a diagram for explaining the case where the absolute difference between the optical output LI monitored during the recording of data on the Nth track and the optical output L0 during the previous one-round recording is equal to or greater than a predetermined value in this embodiment.

[0019] Figure 13 It is a diagram for explaining the case where the absolute difference between the optical output LI monitored during the recording of data on the Nth track and the optical output L0 during the previous one-round recording is equal to or greater than a predetermined value in this embodiment.

[0020] Figure 14 It is a flowchart showing an example of the process of adjusting the optical output in this embodiment.

[0021] Reference Numeral Explanation

[0022] 1…Disk device, 2…Disk, 3…Spindle motor, 4…Actuator assembly, 5…Voice coil motor, 10…Magnetic head, 10W…Write head, 10R…Read head, 30…Near-field optical element, 31…Waveguide, 32…Laser diode, 100…Thermal assist unit, 140…MPU, 160…Memory, 161…Optical output storage unit, 162…Magnetic write width storage unit, 200…Monitoring unit, N…Track Detailed implementation mode

[0023] Hereinafter, with reference to the drawings, the implementation mode will be described. In addition, the disclosure is merely an example, and the invention is not limited to the content described in the following implementation mode. Modifications that can be easily conceived by those skilled in the art are of course included in the scope of the disclosure. For the sake of clarity in the description, in the drawings, there are also cases where the dimensions, shapes, etc. of each part are changed relative to the actual implementation example and are schematically shown. In multiple drawings, there are also cases where the same reference numerals are assigned to corresponding elements and detailed descriptions are omitted.

[0024] (First implementation mode)

[0025] The control configuration of the disk device 1 will be described. Figure 1 It is a block diagram showing an example of the control configuration of the disk device.

[0026] As Figure 1 shown, the disk device 1 includes a disk 2, a spindle motor (SPM) 3, an actuator assembly 4, a voice coil motor (VCM) 5, and a magnetic head 10. A management area 2a for recording information for managing the recorded data is provided on the disk 2.

[0027] Moreover, the disk device 1 includes a head amplifier IC 110, an R / W channel 120, a hard disk controller (HDC) 130, a microprocessor (MPU) 140, a driver IC 150, and a memory 160. In addition, the disk device 1 can be connected to a main computer (host) 170. In addition, the R / W channel 120, the HDC 130, and the MPU 140 may also be assembled in a single-chip integrated circuit.

[0028] The magnetic head 10 includes a write head 10W, a read head 10R, a thermal assist unit 100, and a monitoring unit 200. The write head 10W writes data to the disk 2. The read head 10R reads data from the disk 2. The thermal assist unit 100 assists in writing data when the write head 10W writes data to the disk 2. For the structure of the thermal assist unit 100, refer to Figure 2As described later, the monitoring unit 200 detects the light output of the thermal assist unit 100. In the present embodiment, the monitoring unit 200 is described with the case where a photodetector is assembled to the head 10, but it is not limited thereto. A bolometer may be assembled to the head 10, and the value detected by the bolometer may be converted into the light output. In addition, as a data writing method of the disk device 1, there are a shingled recording method and a conventional recording method, but the write head 10W in the present embodiment is configured to write data by the shingled recording method.

[0029] The spindle motor 3 is driven by a drive current (or drive voltage) supplied from the driver IC 150. The disk 2 records and reproduces a data pattern through the head 10.

[0030] By operating the voice coil by using the voice coil motor 5, the actuator assembly 4 is rotated from the unloading position of a ramp loading mechanism (not shown), and the head 10 is moved to a desired track on the disk 2 and positioned at a predetermined position on the disk 2. The voice coil motor 5 is driven by a drive current (or drive voltage) supplied from the driver IC 150.

[0031] The head amplifier IC 110 supplies a write signal (write current) corresponding to the write data supplied from the R / W channel 120 to the write head 10W. In addition, the light output output from the thermal assist unit 100 is controlled. In addition, the head amplifier IC 110 amplifies the read signal output from the read head 10R and transmits it to the R / W channel 120.

[0032] The R / W channel 120 is a signal processing circuit that processes signals related to reading (read) / writing (write). The R / W channel 120 includes a read channel that performs signal processing of read data and a write channel that performs signal processing of write data. The read channel converts the read signal into digital data and demodulates the read data based on the digital data. The write channel encodes the write data transferred from the HDC 130 and transfers the encoded write data to the head amplifier IC 110.

[0033] The HDC 130 controls the writing of data to the disk 2 and the reading of data from the disk 2 via the head 10, the head amplifier IC 110, the R / W channel 120, and the MPU 140. The HDC 130 constitutes an interface between the disk device 1 and the host 170 and performs transfer control of read data and write data. That is, the HDC 130 functions as a host interface controller that receives signals transferred from the host 170 and transfers signals to the host 170. In addition, the HDC 130 receives commands (write commands, read commands, etc.) transferred from the host 170 and sends the received commands to the MPU 140.

[0034] The MPU 140 is the main controller (control unit) of the disk device 1, and executes control of read / write operations and servo control required for positioning the head 10. Further, the MPU 140 executes processing for preventing degradation of the signal quality recorded on the disk 2, but details of these processes will be described later.

[0035] The drive IC 150 controls the driving of the spindle motor 3 and the voice coil motor 5 according to the control of the MPU 140. By driving the voice coil motor 5, the head 10 is positioned on the target track on the disk 2.

[0036] The memory 160 includes a volatile memory and a non-volatile memory. For example, the memory 160 includes a buffer memory composed of DRAM and a flash memory. The flash memory of the memory 160 stores programs and parameters required for the processing of the MPU 140, and a light output storage unit 161 and a magnetic write width storage unit 162 are provided. The light output storage unit 161 stores the light output monitored by the monitoring unit 200. The magnetic write width storage unit 162 stores the measured magnetic write width. The light output and the magnetic write width are respectively stored in the light output storage unit 161 and the magnetic write width storage unit 162 through the processing described later Figure 10 and are respectively stored in the light output storage unit 161 and the magnetic write width storage unit 162.

[0037] The disk device 1 of the present embodiment includes a head 10 having a thermal assist portion 100 that employs a thermal assist recording method. Figure 2 FIG. is an example of a cross section of the write head portion of the head 10 including the thermal assist portion 100 and the disk 2.

[0038] The disk 2 is a recording medium having, on a substrate 20: a perpendicular recording layer 23 having a large anisotropy in a direction perpendicular to the disk surface of the disk 2; a crystal orientation layer 22 disposed in a lower portion of the perpendicular recording layer 23 to improve the orientation of the perpendicular recording layer 23; a heat sink layer 21 disposed in a lower portion of the crystal orientation layer 22 to suppress an increase in the heated area; and a protective film 24 disposed on an upper portion of the perpendicular recording layer 23.

[0039] The head 10 is a separated type head in which a recording head and a reproducing head are separated, and the recording head portion is configured to have: a main magnetic pole 40 that generates a magnetic field in a direction perpendicular to the disk surface and is formed of a high magnetic permeability material; a trailing yoke 50 that causes magnetic flux to flow to the main magnetic pole 40 and is magnetically coupled to the main magnetic pole; a return shield magnetic pole 60 disposed on a leading side of the main magnetic pole 40 and provided to efficiently close the magnetic path directly below the main magnetic pole; a coil 70 configured to wind around a magnetic path including the trailing yoke and the return shield magnetic pole to cause magnetic flux to flow to the main magnetic pole 40; a near-field light element 30 that generates near-field light for heating the recording layer of the recording medium on the leading side of the main magnetic pole 40; and a waveguide 31 for propagating light for generating the near-field light.

[0040] The light source is assembled in the form of a laser diode 32 mounted on a slider. The near-field light element 30 preferably contains Au, Pd, Pt, Rh, or Ir, or an alloy composed of a combination of several of them. The insulating layer between the main magnetic pole 40 and the near-field light element 30 is preferably an oxide containing SiO2, Al2O3, etc.

[0041] Here, the technology of the disk device will be described.

[0042] There is a known disk device that writes data by the zone recording method and assists in writing the data by a thermal assist unit. In such a disk device, there is a known technology: before writing data, the heating temperature of the disk 2 or the signal quality is confirmed, and the laser power and write offset are adjusted, and then the track is recorded on this basis.

[0043] However, in this disk device, mode jumps may also occur during data writing. When a mode jump occurs during the data writing operation, there is a case where the signal quality recorded at the linear recording density (BPI) and track density (TPI) set during the manufacturing process cannot be maintained.

[0044] In such a case, in the disk device, there is also a technology for detecting mode jumps and dealing with the situation where a mode jump has occurred. However, this technology only deals with the case of writing data by the conventional recording method, and there is no response to the case of writing data by the zone recording method.

[0045] Moreover, there is also a technology in the disk device for performing the following processing: monitoring the number of times data has been written to the (N - 1) and (N + 1) tracks adjacent to the N (N: natural number) track, and when the count of the N track exceeds a threshold, rewriting the data to the N track. However, there is no response when a mode jump occurs during data rewriting. For example, as Figure 3 shown, when rewriting data to the N track, when the light output becomes larger, the magnetic write width becomes wider. Thus, as Figure 4 shown, regarding the N track, there is a concern that the signal quality of both the (N - 1) track and the (N + 1) track adjacent to the N track deteriorates at the position indicated by the label D. Moreover, when rewriting data to the N track with a write offset, the signal quality of a certain adjacent track will also deteriorate. In Figure 5 it shows the case where a write offset is performed to the right side of the figure shown, and there is a concern that the signal quality deteriorates at the position indicated by the label D.

[0046] In addition, in a disk device that writes data by the zone recording method as Figure 6 shown, in the case of writing data to the (N + 1) track as Figure 7 shown and in the case of writing data to the...Figure 8 In the case of rewriting data to the N-th track, when writing data, if the optical output increases due to a pattern transition, the magnetic writing width becomes wider due to the influence of adjacent tracks. Therefore, as Figure 7 and Figure 8 shown by reference numeral D, there is a concern about deterioration of the signal quality of adjacent tracks.

[0047] Next, regarding the correction response area in the case of a pattern transition, the technology in a disk device using a conventional recording method will be described. Figure 9 is a diagram showing an example of the distribution of the magnetic writing width when data is written by driving with an arbitrary constant laser current. As Figure 9 shown, the case of recording with the magnetic writing width W0 is the most frequent. However, due to the change in the optical output based on the pattern transition, the case where the magnetic writing width becomes narrower than W0 (to the left of W0 in the figure) and the case where it becomes wider (to the right of W0 in the figure) occur with a certain probability. Since this technology is a conventional recording method, in the case of writing data to the N-th track, if the magnetic writing width becomes wider, there is a concern about deterioration of the signal quality of the (N - 1)-th track and the (N + 1)-th track. As will be described later, for the disk device 1 of the present embodiment, the offset is adjusted, and on this basis, data recording is performed again. Therefore, compared with the correction response area W1 of the disk device, the correction response area can be made larger like the correction response area W2.

[0048] Due to such a pattern transition occurring, there is a concern about deterioration of the signal quality in the disk device. Hereinafter, the disk device 1 of the present embodiment that can prevent such deterioration of the signal quality will be described in detail.

[0049] First, the operation of writing data in the tile recording method will be described. Figure 10 is a flowchart showing an example of the process of storing the optical output and the magnetic writing width executed by the MPU 140. In addition, this process is executed, for example, by the MPU 140 reading a program stored in the memory 160. In addition, the timing of executing this process is before the disk device 1 leaves the factory.

[0050] As Figure 10 shown, the MPU 140 sets the laser current radiated in the inspection area (ST101). Thereby, the optical output output from the heat assist unit 100 is set. Here, the inspection area may be another area of the disk 2 different from the user data area, or may be a part of a band of the user data area. A band is composed of a plurality of track groups, and the tile recording method rewrites data in units of the so-called band.

[0051] Next, the MPU 140 records a check pattern (ST102) for measuring the magnetic write width in track 1 of the check area. In addition, the MPU 140 saves the light output at this time in the output storage unit 161 (ST103). Thus, the light output with respect to track 1 is saved in the light output storage unit 161.

[0052] Next, the MPU 140 measures the magnetic write width of the recorded check pattern (ST104). In addition, the MPU 140 saves the measured magnetic write width in the magnetic write width storage unit 162 (ST105). Thus, the magnetic write width with respect to track 1 is saved in the magnetic write width storage unit 162.

[0053] As described above, while changing the setting of the laser current value, the MPU 140 repeatedly performs the processes of storing the light output emitted from the laser diode 32 and the magnetic write width written in the check area at this time in the light output storage unit 161 and the magnetic write width storage unit 162 respectively (steps ST101 to ST105). Thus, the relationship between the light output and the magnetic write width can be obtained.

[0054] Next, the process of writing data will be described. Figure 11 It is a flowchart showing an example of the process of performing one-round recording on the target track in the user data area, which is executed by the MPU 140. In addition, this process is executed, for example, by the MPU 140 reading the program stored in the memory 160. In addition, the timing of executing this process is after the disk device 1 leaves the factory.

[0055] The MPU 140 monitors the one-round recording light output L1 (ST201). Specifically, at any timing during the period of recording one-round data on the target track, the light output L1 is monitored by the monitoring unit 200. The monitoring result of this monitoring unit 200 is held in the memory 160, for example.

[0056] Next, the MPU 140 calculates the absolute difference from the light output L0 at the time of the previous one-round recording, and determines whether the absolute difference is equal to or greater than a predetermined value (ST202). If the MPU 140 determines that the absolute difference is not equal to or greater than the predetermined value (ST202: No), the process ends.

[0057] On the other hand, if it is determined that the absolute difference is equal to or greater than the predetermined value (ST202: Yes), the MPU 140 calculates the Δ write offset value based on the value of the light output L1 - light output L0 (ST203). More specifically, the MPU 140 determines, according to the relationship between the light output stored in the light output storage unit 161 and the magnetic write width stored in the magnetic write width storage unit 162 through the above-described Figure 10 process, half of the difference between the magnetic write width W1 corresponding to the light output LI and the magnetic write width W0 corresponding to the light output L0 as the Δ write offset value.

[0058] Next, the MPU 140 determines whether the optical output L0 > the optical output L1 is satisfied (ST204). When it is determined that the optical output L0 > the optical output L1 is satisfied (ST204: Yes), if the MPU 140 has performed a recording operation on the Nth track through step ST201, the position of the write head 10W is controlled in such a way that it is offset by a Δ write offset amount to the same Nth track (ST205). After that, the process proceeds to the aforementioned step ST201.

[0059] In addition, when it is determined that the optical output L0 > the optical output L1 is not satisfied (ST204: No), if the MPU 140 has performed a recording operation on the Nth track through step ST201, the position of the write head 10R is controlled in such a way that it is offset by a Δ write offset amount to the (N - 1)th track, which is the previous track (ST206). After that, the process proceeds to the aforementioned step ST201. As in the process of step ST206, when rewriting data on the (N - 1)th track, which is the previous track, for example, there are ways of rewriting after reading the (N - 1)th track or ways of always retaining one-week worth of write data in the buffer for rewriting because it is zone recording.

[0060] When writing data with a Δ write offset amount offset through step ST205 or ST206, the optical output LI is also monitored (ST201). Here, when the determination in the process of step ST202 is Yes, it is necessary to change the previously set Δ write offset. Regarding the change of the Δ write offset, if the previously set Δ write offset value is set as the first offset value and the newly calculated Δ write offset value in the process of step ST203 is set as the second offset value, the newly set Δ write offset value is determined as the first offset value + the second offset value. In this way, the MPU 140 always monitors the optical output during data writing and changes the Δ write offset amount. Thus, the disk device 1 can cope with the occurrence of a pattern jump. When this process ends, it proceeds to the next track, and the position of the write head 10W is controlled in such a way that it is offset by the Δ write offset amount set through the process of the aforementioned step ST203 to start writing data on the next track.

[0061] Next, referring to Figure 12 、 Figure 13 ,the state of the track on which data has been recorded through the process shown in Figure 11 will be described. Figure 12 、 Figure 13 are cases where the absolute difference between the optical output LI monitored during the recording of data on the Nth track and the optical output L0 during the previous one-week recording is equal to or greater than a predetermined value. Specifically, Figure 12This is the case where the optical output L0 > the optical output L1. That is, it is a schematic diagram showing an example of the state of the track on which data has been recorded through the process of step ST205. Figure 13 This is the case where the optical output L0 < the optical output L1. That is, it is a schematic diagram showing an example of the state of the track on which data has been recorded through the process of step ST206. In addition, whether Figure 12 or Figure 13 , in the case where the upper part of the illustration is the technology (other technology) of the disk device of the present embodiment and the lower part of the illustration is the case of the present embodiment.

[0062] In Figure 12 , in the case of the technology of the disk device, the magnetic writing width of the N-th track is narrow. Therefore, the remaining width of the (N - 1)-th track becomes wider compared to the setting at the time of manufacture, and tracks with different TPIs are locally generated within the band. In contrast, in the present embodiment, by controlling the position of the write head 10W by an offset Δ write offset amount and rewriting data to the N-th track, the remaining width of the (N - 1)-th track is constant and the TPI within the band remains unchanged.

[0063] In addition, in Figure 13 , in the case of the technology of the disk device, the magnetic writing width of the N-th track is wide. Therefore, the remaining width of the (N - 1)-th track becomes narrower compared to the setting at the time of manufacture, and the signal quality of the (N - 1)-th track cannot be maintained. In contrast, in the present embodiment, by controlling the position of the write head 10W by an offset Δ write offset amount, data is rewritten from the (N - 1)-th track. Thus, the remaining width of the (N - 1)-th track remains unchanged compared to other tracks, and the TPI can be maintained.

[0064] According to the disk device 1 that records data in the tile recording manner as described above and has the thermal assist unit 100, when a mode jump occurs, the write offset amount is adjusted, and on this basis, data writing can be performed again. Thus, the disk device 1 can maintain the quality of the signal recorded at the recording density (BPI) and track density (TPI) set during the manufacturing process. In addition, since the disk device 1 adopts the tile recording manner, different from the conventional recording manner, after data is recorded again on the N-th track, data can be rewritten to the (N + 1)-th track. Moreover, as Figure 9 shown, in the technology of the disk device described above, compared with the case of the present embodiment, the correction response area W1 is limited. However, compared with the technology of the disk device, even if the track width becomes wider, since the correction response area W2 is large, deterioration of the quality of the signal recorded on the disk 2 can be prevented.

[0065] (Second Embodiment)

[0066] In the second embodiment, the disk device 1 that executes processing corresponding to a state where the light output does not satisfy a predetermined lower limit value will be described. In addition, the same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0067] Figure 14 FIG. is a flowchart showing an example of the processing for adjusting the light output executed by the MPU 140. In addition, this processing is executed, for example, by the MPU 140 reading a program stored in the memory 160. In addition, the timing for executing this processing is before the processing described above Figure 11 is executed.

[0068] As Figure 14 shown, the MPU 140 monitors the light output LI at any timing during one round of recording of a track (ST301). Next, the MPU 140 determines whether the light output L1 is equal to or greater than a predetermined value (ST302). When it is determined by the MPU 140 that the light output L1 is equal to or greater than the predetermined value (ST302: Yes), the processing ends. The subsequent processing is the same as that described above Figure 11 is the same.

[0069] On the other hand, when it is determined that the light output L1 is not equal to or greater than the predetermined value (ST302: No), the MPU 140 records data on the track again, and monitors the light output L2 at any timing during the recording (ST303). Next, the MPU 140 determines whether the light output L2 is equal to or greater than a predetermined value (ST304). When it is determined that the light output L2 is equal to or greater than the predetermined value (ST304: Yes), in step ST301, when data has been written to the Nth track, the same Nth track is written with data again. In addition, when it is determined that the light output L2 is not equal to or greater than the predetermined value (ST304: No), the process returns to step ST303, and the monitoring of the light output L2 continues.

[0070] When the light output L1 does not satisfy the predetermined value, the medium recording layer of the disk 2 is in a state where heating is insufficient, so the signal quality of the track on which data has been recorded cannot be maintained. In contrast, in the disk device 1 of the present embodiment, by writing data again from when the light output L1 becomes equal to or greater than the predetermined value, it is possible to prevent deterioration of the signal quality of the track on which data has been written.

[0071] In the first and second embodiments described above, the MPU 140 monitors the light output at any timing during one round of recording, but the monitoring may be performed two or more times during one round. In addition, since it is not clear in which range of one round the mode jump occurs, for example, the light output may be monitored in units of sectors.

[0072] In addition, although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel 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 / or their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope of equivalents thereof.

Claims

1. A disk device, comprising: A disk; A magnetic head having a write head for writing data to the disk, a thermal assist unit for assisting the writing of data of the write head using a near-field light element, and a read head for reading data from the disk; A monitoring unit for monitoring the light output; and A control unit for controlling the reading of data from the disk by the magnetic head and the writing of data to the disk based on the zone recording method, When writing the data to the first track, the control unit controls the position of the write head and rewrites the data to the first track or a second track one track ahead of the first track when the absolute difference between the light output monitored by the monitoring unit during writing and the light output monitored by the monitoring unit in the previous time exceeds a predetermined value.

2. The disk device according to claim 1, The control unit controls the position of the write head based on an offset amount offset in the radial direction of the disk.

3. The disk device according to claim 2, The control unit calculates the offset amount based on a change amount of the magnetic write width based on the light output monitored by the monitoring unit during the writing of the data and the light output monitored by the monitoring unit during the previous execution of the writing of the data.

4. The disk device according to claim 1, The monitoring unit monitors the light output two or more times during the writing of data to the first track.

5. The disk device according to claim 1, When writing the data, the control unit starts writing the data from when the light output becomes equal to or greater than the predetermined lower limit value when the light output is smaller than the predetermined lower limit value.

6. The disk device according to claim 1, The disk includes an inspection area for a recording inspection mode, The disk device comprises: A light output storage unit for storing the light output output to the inspection area and monitored by the monitoring unit; and A magnetic write width storage unit for measuring the inspection mode recorded in the inspection area and storing the measured magnetic write width, The control unit stores the light output and the magnetic write width in the light output storage unit and the magnetic write width storage unit respectively while changing the light output output from the near-field light element.

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