Magnetic disk device

Abstract

To provide a magnetic disk device with a large storage capacity.SOLUTION: A magnetic head performs a magnetization operation to magnetize a magnetic disk with either a first polarity or a second polarity opposite to the first polarity. The magnetization operation includes a first magnetization operation to magnetize with a first recording width and a second magnetization operation to magnetize with a second recording width larger than the first recording width. A controller magnetizes a first area unit to either the first polarity or the second polarity in the first magnetization operation or the second magnetization operation, and then magnetizes a second area unit to the opposite polarity to the first area unit in the second magnetization operation. The second area unit is an area unit radially adjacent to the first area unit, included in a second track, which is adjacent to the first track among a plurality of tracks and written after the first track.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] This embodiment relates to a magnetic disk device. [Background technology]

[0002] In conventional magnetic disk devices, data expressed in binary numbers is written onto the magnetic disk. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 9,858,962 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment is to provide a magnetic disk drive with a large storage capacity. [Means for solving the problem]

[0005] According to one embodiment, a magnetic disk drive includes a magnetic disk, a magnetic head, and a controller. The magnetic disk has a plurality of tracks, each of which includes a plurality of area units arranged along the track. The magnetic head performs a magnetization operation on the magnetic disk to magnetize it to either a first polarity or a second polarity that is opposite to the first polarity. The magnetization operation includes a first magnetization operation that magnetizes the magnetic disk with a first recording width and a second magnetization operation that magnetizes the magnetic disk with a second recording width that is larger than the first recording width. The controller can perform any of the following write operations: a first write operation that writes a first value to the first area unit, a second write operation that writes a second value to the first area unit, and a third write operation that writes a third value to the first area unit. The first area unit is an area unit included in a first track, which is one of the plurality of tracks. The second value is a value different from the first value. The third value is different from both the first value and the second value. In the first write operation, the controller magnetizes the first area unit to a first polarity in the first magnetization operation or the second magnetization operation. In the second write operation, the controller magnetizes the first area unit to a second polarity in the first magnetization operation or the second magnetization operation. In the third write operation, the controller magnetizes the first area unit to either the first polarity or the second polarity in the first magnetization operation or the second magnetization operation, and then magnetizes the second area unit to a polarity opposite to that of the first area unit in the second magnetization operation. The second area unit is an area unit radially adjacent to the first area unit included in a second track that is adjacent to the first track of the multiple tracks and is a track that is written after the first track. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of the magnetic disk according to the first embodiment. [Figure 3] FIG. 3 is a schematic diagram for explaining the SMR method used in the magnetic disk device of the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a plurality of band areas provided on the magnetic disk of the embodiment. [Figure 5] FIG. 5 is another diagram showing an example of a plurality of band areas provided on the magnetic disk according to the embodiment. [Figure 6] FIG. 6 is a diagram for explaining a method for writing ternary information according to the first embodiment. [Figure 7] FIG. 7 is another diagram for explaining the method of writing ternary information according to the first embodiment. [Figure 8] FIG. 8 is yet another diagram for explaining the method of writing ternary information according to the first embodiment. [Figure 9] FIG. 9 is a diagram showing a list of setting patterns of write currents in two digit areas adjacent to each other in the radial direction in the first embodiment. [Figure 10] FIG. 10 illustrates an example of a write operation of the magnetic disk device of the first embodiment. [Figure 11] FIG. 11 is a flowchart showing an example of the operation of setting the write current according to the first embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of a write operation to an additional track in the first embodiment. [Figure 13] FIG. 13 is a diagram illustrating an example of a write data generation method executed by the controller of the second embodiment. [Figure 14] FIG. 14 is a diagram for explaining a method for writing a value that can take on four levels according to the third embodiment. [Figure 15] FIG. 15 is a diagram for explaining an example of a method for controlling the print width according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The magnetic disk drive according to the embodiment will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

[0008] (First embodiment) FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device 1 according to the first embodiment.

[0009] The magnetic disk device 1 is connected to a host 2. The magnetic disk device 1 can receive access commands such as write commands and read commands from the host 2.

[0010] The magnetic disk device 1 includes a magnetic disk 11 having a recording surface formed on its surface. The magnetic disk device 1 writes and reads data to and from the magnetic disk 11 (more precisely, the recording surface of the magnetic disk 11) in response to an access command. Although the magnetic disk device 1 may include multiple magnetic disks 11, in this embodiment, for the sake of simplicity of explanation and illustration, the magnetic disk device 1 is shown to include one magnetic disk 11.

[0011] Data is written and read via a magnetic head 22. Specifically, the magnetic disk device 1 includes, in addition to a magnetic disk 11, a spindle motor 12, a motor driver IC (Integrated Circuit) 21, a magnetic head 22, an actuator arm 15, a voice coil motor (VCM) 16, a ramp 13, a head IC 24, a read / write channel (RWC) 25, RAM 27, a FROM (Flash Read Only Memory) 28, a buffer memory 29, a hard disk controller (HDC) 23, and a processor 26.

[0012] The magnetic disk 11 is rotated at a predetermined rotation speed by a spindle motor 12 attached to the rotation shaft of the magnetic disk 11. The spindle motor 12 is driven by a motor driver IC 21.

[0013] The motor driver IC 21 controls the rotation of the spindle motor 12 and the rotation of the VCM 16 .

[0014] The magnetic head 22 uses a write element 22w and a read element 22r provided therein to write and read data to and from the magnetic disk 11. The magnetic head 22 is attached to the tip of an actuator arm 15. The magnetic head 22 is moved in the radial direction of the magnetic disk 11 by a VCM 16 driven by a motor driver IC 21.

[0015] When the magnetic disk 11 is stopped from rotating, the magnetic head 22 is moved onto the ramp 13. The ramp 13 is configured to hold the magnetic head 22 at a position spaced apart from the magnetic disk 11.

[0016] During reading, the head IC 24 amplifies and outputs the signal read from the magnetic disk 11 by the magnetic head 22 and supplies it to the RWC 25. The head IC 24 also amplifies the signal corresponding to the data to be written that is supplied from the RWC 25 and supplies it to the magnetic head 22.

[0017] The HDC 23 controls the transmission and reception of data to and from the host 2 via the I / F bus, controls the buffer memory 29, and performs error correction processing on the read data.

[0018] The buffer memory 29 is used as a buffer for data transmitted to and received from the host 2. For example, the buffer memory 29 is used to temporarily store data to be written to the magnetic disk 11 or data read from the magnetic disk 11.

[0019] The buffer memory 29 is configured, for example, by a volatile memory capable of high-speed operation. The type of memory that configures the buffer memory 29 is not limited to a specific type. The buffer memory 29 can be configured, for example, by a dynamic random access memory (DRAM), a static random access memory (SRAM), or a combination of these.

[0020] The RWC 25 modulates the data to be written that is supplied from the HDC 23 and supplies it to the head IC 24. The RWC 25 also demodulates the signal that is read from the magnetic disk 11 and supplied from the head IC 24 and outputs it to the HDC 23 as digital data.

[0021] The processor 26 is, for example, a CPU (Central Processing Unit). A RAM 27, a FROM (Flash Read Only Memory) 28, and a buffer memory 29 are connected to the processor 26.

[0022] The FROM 28 is a non-volatile memory. Firmware (program data), various operating parameters, etc. are stored in the FROM 28. The firmware may be stored on the magnetic disk 11.

[0023] The RAM 27 is configured by, for example, DRAM, SRAM, or a combination of these. The RAM 27 is used as an operating memory by the processor 26. The RAM 27 is used as an area into which firmware is loaded and an area in which various management data is held.

[0024] The processor 26 performs overall control of the magnetic disk device 1 in accordance with firmware stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads firmware from the FROM 28 or the magnetic disk 11 into the RAM 27, and controls the motor driver IC 21, head IC 24, RWC 25, HDC 23, etc. in accordance with the loaded firmware.

[0025] The configuration including the RWC 25, the processor 26, and the HDC 23 can also be considered as the controller 30. The controller 30 may be configured as a System-On-a-Chip (SoC). The controller 30 does not necessarily have to be configured as a SoC. In addition to these, the controller 30 may also include other elements (for example, a RAM 27, a ROM 28, a buffer memory 29, or the RWC 25).

[0026] 2 is a schematic diagram showing an example of the configuration of the magnetic disk 11 according to the first embodiment. This diagram shows an example of the rotation direction of the magnetic disk 11. The magnetic head 22 moves relative to the magnetic disk 11 as the magnetic disk 11 rotates. Therefore, the write / read direction, i.e., the direction in which data is written or read by the magnetic head 22 along the circumferential direction, is opposite to the rotation direction of the magnetic disk 11.

[0027] During the manufacturing process, servo information is written to the magnetic disk 11 by, for example, a servo writer or by self-servo writing (SSW). Fig. 2 shows radially arranged servo areas 42 as an example of the arrangement of servo areas in which servo information is written. Data areas 43 in which data can be written are provided between the servo areas 42.

[0028] Based on servo information, a plurality of concentric tracks 41 are set in the radial direction of the magnetic disk 11. A plurality of data areas 43 are provided along the tracks 41, and a plurality of sectors in which data is written are arranged.

[0029] Known methods for writing data to a magnetic disk include a method called SMR (Shingled Magnetic Recording) and a method called CMR (Conventional Magnetic Recording).

[0030] 3 is a schematic diagram illustrating the SMR method used in the magnetic disk device 1 of the first embodiment. In the SMR method, when data (referred to as first data) on a certain track 41 is written and then data (referred to as second data) on a track 41 radially adjacent to the track 41 is written, the tracks 41 are arranged so that the second data overlaps a portion of the first data. In other words, according to the SMR method, data on one of two tracks 41 radially adjacent to each other on the magnetic disk 11 is written so as to overlap a portion of data on the other of the two tracks 41.

[0031] For example, data on track #2 is written so that it overlaps part of the data already written on track #1. Similarly, data on track #3 is written so that it overlaps part of the data already written on track #2. In other words, according to the SMR method, data on one track repeatedly overlaps part of the data already written on an adjacent track.

[0032] This makes each track width TW narrower than the width (WHw) of the write element 22w, thereby improving the recording density.

[0033] However, with the SMR system, because the track width TW is narrower than the width WHw of the write element 22w, updating a portion of the data for multiple tracks destroys the data on tracks adjacent to the updated data. To prevent this data destruction, the data for multiple tracks, including the portion of the data, is updated in a lump. The area of ​​multiple tracks that is updated in a lump is called a band.

[0034] Furthermore, according to the SMR method, writing to a plurality of tracks 41 within one band is permitted only from a predetermined end of the outer periphery or the inner periphery of the magnetic disk to the predetermined other end. In the example shown in FIG. 3, writing is performed for each track 41 from the outer periphery end toward the inner periphery end. The controller 30 may also be configured to perform writing for each track 41 from the inner periphery end toward the outer periphery end. The order of writing may also be set individually for each band.

[0035] 4 and 5 are diagrams showing examples of a plurality of band areas provided on the magnetic disk 11 of the embodiment.

[0036] The recording surface 100 of the magnetic disk 11, i.e., the area where the tracks 41 can be arranged, is divided radially into multiple storage areas 110. The multiple storage areas 110 include one media cache area 120 and multiple band areas 130. Areas called guard areas 140 that cannot be specified as write destinations by the host 2 are provided between the storage areas 110.

[0037] The storage area 110 provided on the outermost radial side of the recording surface 100 is set as a media cache area 120. The media cache area 120 is a storage area used as a temporary storage location for data. Note that the location of the media cache area 120 is not limited to the outermost radial side. Two or more media cache areas 120 may be provided on the recording surface. Data can be written to the media cache area 120 using the CMR method.

[0038] One or more of the multiple storage areas 110 are set as band areas 130. Multiple tracks 41 are provided in each band area 130. In each band area 130, data is written to all of the tracks 41 using the SMR method. When writing data to each band area 130, writing data from the band area 130 that is the write destination to an adjacent band area 130 across a guard area 140 is prohibited.

[0039] Note that data may be written in the CMR method in some of the multiple band areas 130. The band areas 130 in which data is written in the SMR method will be described below.

[0040] When writing is performed on multiple tracks 41 in one band area 130 using the SMR method, the track 41 that is written first and located at one end of the multiple tracks 41 in the radial direction is referred to as the head track of the band area 130. The track 41 that is written last and located at the other end of the multiple tracks 41 in the radial direction is referred to as the end track of the band area 130.

[0041] Data can be considered as a string of multiple values. A string of multiple values ​​is written along the track 41 in the sectors of each track 41. In other words, each sector can be considered to have a structure in which multiple area units, each capable of holding a single-digit value, are arranged in a row along the track 41. Each area unit capable of holding a single-digit value is referred to as a digit area.

[0042] When a positive write current is supplied to the magnetic head 22, the magnetic head 22 can magnetize to a positive polarity the portion of the recording surface 100 of the magnetic disk 11 where the magnetic head 22 is located. When a negative write current is supplied to the magnetic head 22, the magnetic head 22 can magnetize to a negative polarity the portion of the recording surface 100 of the magnetic disk 11 where the magnetic head 22 is located. The controller 30 controls the write current when the magnetic head 22 passes over each digit area, depending on the value to be written in each digit area.

[0043] Here, a technology (hereinafter referred to as a comparative example) to be compared with the embodiment will be described. According to the comparative example, a value that can take two levels is written per digit area. That is, data is written to the magnetic disk as information expressed in binary. More specifically, in a write operation, the polarity of magnetization in the digit area is set to a polarity corresponding to a value of either positive or negative. In a read operation, based on a signal obtained by the magnetic head, it is determined whether the polarity of magnetization in the digit area is positive or negative, and a value corresponding to the determined polarity is obtained.

[0044] In this embodiment, a value that can take three levels is written per digit area. In other words, data is written to the magnetic disk 11 as information expressed in ternary notation. This allows for a larger storage capacity than the magnetic disk device according to the comparative example, without increasing the number of digit areas.

[0045] 6 to 8 are diagrams for explaining a method for writing ternary information according to the first embodiment. In the following explanation, it is assumed that each track 41 is assigned a track number corresponding to the arrangement order in the radial direction, and that writing is performed for each track 41 in the order of track numbers in the SMR method.

[0046] Here, an example is explained in which ternary information is written to three radially consecutive tracks: track #n, track #n+1, and track #n+2. Note that data is written to track #n, track #n+1, and track #n+2 in that order.

[0047] 6 and subsequent explanations, the value written to one digit area can be "-1," "0," or "1," each of which corresponds to a different level. Data written to track 41 will be referred to as write data.

[0048] As shown in part (A) of Figures 6 to 8, the write data for track #n is a sequence of values ​​"-1, 1, 0, -1, 0, 1, 1, -1, 0, 1". The write data for track #n+1 is a sequence of values ​​"1, 1, -1, 0, 1, 1, 0, -1, 1, -1". The write data for track #n+2 is a sequence of values ​​"-1, -1, -1, 1, 1, -1, 1, -1, -1, 1".

[0049] The controller 30 also controls the write currents supplied to the magnetic head 22 to be WC2, WC1, WC -1 , and W.C. -2 WC1 and WC2 are positive write currents, and the current amount of WC2 is greater than the current amount of WC1. In other words, the current amount is the absolute value of the amplitude of the current value. WC -1 and W.C. -2 is the negative write current, and WC -2 The current amount of WC -1 The current flowing through WC2 is greater than that of WC -2 The current amount of WC1 is approximately equal to that of WC -1 The current amount is approximately equal to that of

[0050] The current flowing through WC2 is -2 The current amount of WC1 is not equal to WC -1For example, if the characteristics are different between the positive and negative polarities, the same recording quality cannot be obtained even if the same amount of current is supplied to the magnetic head 22 for both the positive and negative polarities. In such a case, the amount of current for WC2 is set to be equal to that for WC3. -2 The current amount of WC1 is not equal to WC -1 In other words, the current amount of WC2 and the current amount of WC -2 The current amount of WC1 and the current amount of WC2 can be set to different values ​​to obtain the same recording width. -1 The current amount can be set to a different value to obtain the same recording width.

[0051] When a write current of WC1 is supplied, the recording width in the radial direction by the magnetic head 22 is WC -1 The radial recording width of the magnetic head 22 when a write current of WC1 is supplied is approximately equal to the radial recording width of the magnetic head 22 when a write current of WC2 is supplied. -2 WC2 or WC3 is approximately equal to the radial recording width of the magnetic head 22 when a write current of WC3 or WC4 is supplied. -2 When a write current of WC1 or WC2 is supplied, the recording width in the radial direction by the magnetic head 22 is -1 is larger than the radial recording width of the magnetic head 22 when a write current of .gtoreq.1 is supplied.

[0052] As shown in Fig. 6, first, the controller 30 executes a write operation on track #n. In the write operation on track #n, if the value to be written is "1", the controller 30 supplies a write current of WC1 to the magnetic head 22, thereby magnetizing the digit area of ​​the write destination to positive polarity. If the value to be written is "-1", the controller 30 supplies a write current of WC1 to the magnetic head 22, thereby magnetizing the digit area of ​​the write destination to positive polarity. -1 This supplies a write current of 0.01 V to the digit area to be written to, thereby magnetizing the digit area to a negative polarity.

[0053] Here, any three digit areas aligned in the radial direction will be referred to as the first digit area, the second digit area, and the third digit area. The second digit area is a digit area included in a track 41 that is adjacent to the first digit area in the radial direction and that is written after the track 41 that includes the first digit area. The third digit area is a digit area included in a track 41 that is adjacent to the first digit area in the radial direction and that is written before the track 41 that includes the first digit area.

[0054] If the value written to the first digit area is "0", the controller 30 sets the direction of the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the first digit area to be opposite to the direction of the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the second digit area.

[0055] Specifically, when the value written in the second digit area is "1," the controller 30 sets the write current when the magnetic head 22 passes over the second digit area to a positive current, and therefore, when the magnetic head 22 passes over the first digit area to a negative current.

[0056] If the value written in the second digit area is "-1," the controller 30 sets the write current when the magnetic head 22 passes over the second digit area to a negative current, and therefore sets the write current when the magnetic head 22 passes over the first digit area to a positive current.

[0057] For example, the value written in digit area D1 included in track #n is "0." If digit area D1 is considered to be the first digit area, then digit area D2 included in track #n+1 corresponds to the second digit area. The value written in digit area D2 is "-1," which causes the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D2 to be negative. Therefore, controller 30 causes the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D1 to be positive. Here, controller 30 supplies a write current of WC1 to magnetic head 22 in digit area D1.

[0058] In another example, the value written in digit area D3 included in track #n is "0." If digit area D3 is considered to be the first digit area, digit area D4 included in track #n+1 corresponds to the second digit area. The value written in digit area D4 is "1," which causes the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D4 to be a positive current. Therefore, when magnetic head 22 passes over digit area D3, controller 30 causes the write current supplied to magnetic head 22 to be a negative current. Here, controller 30 writes WC to magnetic head 22 in digit area D3. -1 supplies a write current of

[0059] As shown in FIG. 7, the controller 30 executes a write operation on track #n, followed by a write operation on track #n+1.

[0060] In a write operation for track #n+1, if the value to be written is "1", the controller 30 supplies a positive write current to the magnetic head 22, thereby magnetizing the digit area to be written to a positive polarity. If the value to be written is "-1", the controller 30 supplies a negative write current to the magnetic head 22, thereby magnetizing the digit area to be written to a negative polarity.

[0061] If the value written in the first digit area is "1" or "-1", the controller 30 determines the amount of write current to supply to the magnetic head 22 when passing through the first digit area based on whether the value written in the third digit area is "0" or not.

[0062] Specifically, when the value written in the third digit area is "1" or "-1", the controller 30 controls the write current when the magnetic head 22 passes over the first digit area to be either WC1 or WC2. -1 When the value written in the third digit area is "0", the controller 30 sets the write current when the magnetic head 22 passes over the first digit area to WC2 or WC3. -2 Let's say.

[0063] As mentioned above, WC2 or WC -2 When a write current of WC1 or WC2 is supplied, the recording width in the radial direction by the magnetic head 22 is -1 This is larger than the radial recording width of the magnetic head 22 when a write current of 1 / 3 is supplied. As a result, a write operation to the first digit area magnetizes not only the first digit area but also part of the third digit area.

[0064] The polarity of magnetization in the third digit area is opposite to the polarity of magnetization in the first digit area. Therefore, a write operation to the first digit area reverses the polarity of a portion of the third digit area. As a result, when the third digit area is read by the magnetic head 22, a signal of a level (referred to as the third level) different from both the level (referred to as the first level) obtained when the entire digit area is positive polarity and the level (referred to as the second level) obtained when the entire digit area is negative polarity is obtained. In the examples shown in FIGS. 6 to 8, the first level corresponds to "1." The second level corresponds to "-1." The third level corresponds to "0."

[0065] For example, the value written in the digit area D2 is "-1." If the digit area D2 is considered to be the first digit area, the digit area D1 included in the track #n corresponds to the third digit area. The value written in the digit area D1 is "0." Therefore, the controller 30 sets the write current supplied to the magnetic head 22 when the magnetic head 22 passes over the digit area D2 as WC -2 The controller 30 causes the magnetic head 22 to write WC when the magnetic head 22 passes through the digit area D2. -2 By supplying a write current of 1, a part (here, half) of the digit area D1 in the radial direction is inverted from positive to negative polarity, thereby changing the magnetization state of the digit area D1 to a state where a third level signal is obtained in a read operation.

[0066] In another example, the value written to digit area D4 is "1." If digit area D4 is considered to be the first digit area, then digit area D3 included in track #n corresponds to the third digit area. The value written to digit area D3 is "0." Therefore, the controller 30 sets the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D3 to WC2. By supplying a write current of WC2 to magnetic head 22 when magnetic head 22 passes over digit area D4, the controller 30 reverses a portion (here, half) of digit area D3 from negative polarity to positive polarity. This causes the magnetization state of digit area D3 to be in a state in which a third level signal is obtained during a read operation.

[0067] In this way, the controller 30 determines the magnetization state of the digit area based on three values: whether the entire digit area should be positive, the entire digit area should be negative, or only a portion of the digit area should be positive or negative. During a read operation, the controller 30 obtains the written value by determining whether the signal level obtained from the magnetic head 22 corresponds to the first level, second level, or third level. This enables writing and reading of ternary information.

[0068] In write operations on track #n+1 and any other track 41, if the value to be written is "0", the controller 30 determines the direction of the write current to be supplied to the magnetic head 22 when the magnetic head 22 passes through the digit area (first digit area) to which the data is to be written, so that the direction is opposite to the direction of the write current to be supplied to the magnetic head 22 when the magnetic head 22 passes through the second digit area.

[0069] For example, the value written in digit area D5 included in track #n+1 is "0." If digit area D5 is considered to be the first digit area, then digit area D6 included in track #n+2 corresponds to the second digit area. The value written in digit area D6 is "1," which causes the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D6 to be a positive current. Therefore, when magnetic head 22 passes over digit area D5, controller 30 causes the write current supplied to magnetic head 22 to be a negative current. Here, controller 30 writes WC to magnetic head 22 in digit area D5. -1 supplies a write current of

[0070] Furthermore, the value written in digit area D7 included in track #n+1 is "0." If digit area D7 is considered to be the first digit area, digit area D8 included in track #n+2 corresponds to the second digit area. The value written in digit area D8 is "1," which causes the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D8 to be a positive current. Therefore, controller 30 causes the write current supplied to magnetic head 22 when magnetic head 22 passes over digit area D7 to be a negative current. Here, controller 30 writes WC to magnetic head 22 in digit area D7. -1 supplies a write current of

[0071] As shown in FIG. 8, the controller 30 executes a write operation to track #n+2 following a write operation to track #n+1.

[0072] In a write operation for track #n+2, the direction and amount of the write current in each digit area are set in the same manner as in the write operations for track #n and track #n+1. The direction and amount of the write current in the first digit area are set based on the value written in the first digit area, the polarity of the write current in the second digit area, and the value written in the third digit area.

[0073] For example, the value written in digit area D6 is "1." If digit area D6 is considered to be the first digit area, then digit area D5 included in track #n+1 corresponds to the third digit area. The value written in digit area D5 is "0." Therefore, the controller 30 sets the write current supplied to the magnetic head 22 when the magnetic head 22 passes over digit area D6 to WC2. By supplying the write current of WC2 to the magnetic head 22 when the magnetic head 22 passes over digit area D6, the controller 30 reverses a portion (here, half) of the digit area D5 from negative polarity to positive polarity. This causes the magnetization state of digit area D5 to be in a state in which a third level signal is obtained during a read operation.

[0074] Also, for example, the value written to digit area D8 is "1." If digit area D8 is considered to be the first digit area, then digit area D7 included in track #n+1 corresponds to the third digit area. The value written to digit area D7 is "0." Therefore, the controller 30 sets the write current supplied to the magnetic head 22 when the magnetic head 22 passes over digit area D8 to WC2. By supplying the write current of WC2 to the magnetic head 22 when the magnetic head 22 passes over digit area D8, the controller 30 reverses a portion (here, half) of the digit area D7 from negative polarity to positive polarity. This causes the magnetization state of digit area D7 to be in a state in which a third level signal is obtained during a read operation.

[0075] 9 is a diagram showing a list of setting patterns of write currents in two digit areas Da and Db that are adjacent to each other in the radial direction in the first embodiment. Digit area Da is included in track #i, and digit area Db is included in track #i+1, which is track 41 that is written after track #i.

[0076] 9, when the value written to the digit area Da is "1" or "-1", the direction of the write current in the digit area Da is set only according to the value written to the digit area Da, regardless of the value written to the digit area Db. When the value written to the digit area Da is "1", the write current in the digit area Da is set to a positive current. When the value written to the digit area Da is "-1", the write current in the digit area Da is set to a negative current.

[0077] When the value written to digit area Da is "0," the direction of the write current in digit area Da is set according to the direction of the write current in digit area Db. When the value written to digit area Da is "0" and the value written to digit area Db is "1," the write current in digit area Da is negative and the write current in digit area Db is positive. When the value written to digit area Da is "0" and the value written to digit area Db is "-1," the write current in digit area Da is positive and the write current in digit area Db is negative. When the value written to digit area Da is "0" and the value written to digit area Db is "0," the direction of the write current in digit areas Da and Db is set according to the direction of the write current in the digit area other than digit area Da, of the two digit areas radially adjacent to digit area Db. In FIG. 9, when the value written to the digit area Da is "0" and the value written to the digit area Db is "0", the direction of the write current in the digit areas Da and Db is shown as undetermined.

[0078] The amount of the write current in the digit area Da is set depending on whether the value written in the digit area (referred to as the digit area Dc) other than the digit area Db, one of the two digit areas radially adjacent to the digit area Da, is "0". When the value written in the digit area Dc is "1" or "-1", the write current in the digit area Da is set to either WC1 or WC2. -1 When the value written to the digit area Dc is "0", the write current in the digit area Da is set to WC2 or WC3 in order to invert the polarity of a part of the digit area Dc. -2 It is said that.

[0079] Next, the operation of the magnetic disk device 1 of the first embodiment will be described.

[0080] FIG. 10 is a diagram showing an example of a write operation of the magnetic disk device 1 of the first embodiment.

[0081] First, the controller 30 prepares write data for a plurality of tracks that are continuous in the radial direction in the buffer memory 29 (S101).

[0082] The write data prepared in S101 is information expressed in ternary numbers. The controller 30 may receive data expressed in binary numbers from the host 2 and generate write data expressed in ternary numbers by performing conversion on the received data expressed in binary numbers. The generation of the write data may be performed by the RWC 25 included in the controller 30. In such a case, the RWC 25 transmits write data with the previous track as the write destination to the head IC 24 and stores a copy of the write data in the buffer memory 29.

[0083] Alternatively, the controller 30 may receive write data expressed in ternary from the host 2 and store the received write data in the buffer memory 29.

[0084] In addition, if, for example, p (p is an integer equal to or greater than 2) digit areas into which "0" is written are arranged radially, the direction of the write current in the p digit areas into which "0" is written cannot be set unless the value written in the digit area adjacent to the p digit areas into which "0" is written is determined to be either "1" or "-1." Therefore, an upper limit on the number of digit areas into which "0" is written consecutively in the radial direction is set in advance. This upper limit is represented by K (where K is an integer equal to or greater than 2). In other words, the write data of the multiple tracks prepared in the buffer memory 29 in S101 is write data generated under the constraint that the number of digit areas into which "0" is written consecutively arranged radially is K or less.

[0085] The controller 30 sets a write current for each digit area based on the write data prepared in the buffer memory 29 (S102).

[0086] The controller 30 writes the write data prepared in the buffer memory 29 to the magnetic disk 11 (S103). In S103, the controller 30 writes using the set write current.

[0087] After S103, the write operation ends.

[0088] Fig. 11 is a flowchart showing an example of the operation of setting the write current in the first embodiment. The series of operations shown in this figure is executed in the process of S102 shown in Fig. 10. Here, the operation of setting the write current for all digit areas included in one track 41 (a first target track, described later) will be described. The series of operations shown in this figure will be referred to as a setting operation unit.

[0089] First, the controller 30 selects K+1 tracks 41 that are consecutive in the radial direction from among the plurality of tracks for which write data is prepared in the buffer memory 29 (S201). Here, K=2. That is, the controller 30 selects three tracks 41 that are consecutive in the radial direction. Of the selected three tracks 41, the track 41 that is written first will be referred to as the first target track, the track 41 that is written second will be referred to as the second target track, and the track 41 that is written last will be referred to as the third target track.

[0090] Note that a single setting operation unit sets write currents for all digit areas included in the first target track. The setting operation unit is repeatedly executed to set write currents for all digit areas included in all tracks 41 included in one band area 130. For each setting operation unit, the controller 30 changes the selected K+1 tracks 41 one track 41 at a time in a direction corresponding to the write order. For example, if tracks #r, #r+1, and #r+2 are selected in a certain setting operation unit, tracks #r+1, #r+2, and #r+3 are selected in the next setting operation unit.

[0091] The controller 30 selects one digit area from the first target track (S202). The digit area selected in S202 is referred to as the first target digit area.

[0092] The controller 30 determines whether the write current for the first target digit area has already been set (S203).

[0093] In one setting operation unit, the write current in the digit area included in the second target track or the digit area included in the third target track may be set by the processing of S210, S211, S213, or S214 described below. Therefore, among the digit areas included in track 41 selected as the first target track, there may be a digit area for which a write current has already been set in the previous setting operation unit or the setting operation unit before last. In S203, the controller 30 determines whether the write current in the first target digit area has already been set in the previous setting operation unit or the setting operation unit before last.

[0094] If the write current in the first target digit area has not been set (S203: No), the controller 30 determines whether the value to be written in the first target digit area is "0" (S204).

[0095] If the value to be written in the first target digit area is not "0" (S204: No), the controller 30 determines whether the value to be written in the first target digit area is "1" (S205).

[0096] If the value to be written in the first target digit area is "1" (S205: Yes), the controller 30 sets the write current in the first target digit area to WC1 (S206).

[0097] If the value to be written in the first target digit area is not "1" (S205: No), that is, if the value to be written in the first target digit area is "-1", the controller 30 sets the write current in the first target digit area to WC -1 (S207).

[0098] If the value to be written in the first target digit area is "0" (S204: Yes), the controller 30 determines whether the value to be written in the digit area adjacent to the first target digit area included in the second target track is "0" (S208). The digit area adjacent to the first target digit area included in the second target track is referred to as the second target digit area.

[0099] If the value to be written in the second target digit area is not "0" (S208: No), the controller 30 determines whether the value to be written in the second target digit area is "1" (S209).

[0100] If the value to be written in the second target digit area is “1” (S209: Yes), the controller 30 sets the write current in the first target digit area to WC -1 and the write current in the second target digit area is set to WC2 (S210).

[0101] If the value to be written in the second target digit area is not "1" (S209: No), that is, if the value to be written in the second target digit area is "-1", the controller 30 sets the write current in the first target digit area to WC1 and the write current in the second target digit area to WC2. -2 (S211).

[0102] As described above, K is 2. Therefore, if the value written to the first target digit area and the value written to the second target digit area are both "0" (S208: Yes), the value written to the digit area adjacent to the second target digit area included in the third target track is either "1" or "-1." The digit area adjacent to the second target digit area included in the third target track is referred to as the third target digit area. The controller 30 determines whether the value written to the third target digit area is "1" (S212).

[0103] If the value to be written in the third target digit area is “1” (S212: Yes), the controller 30 sets the write current in the first target digit area to WC1 and the write current in the second target digit area to WC2. -2 and the write current in the third target digit area is set to WC2 (S213).

[0104] If the value to be written in the third target digit area is not "1" (S212: No), that is, if the value to be written in the third target digit area is "-1", the controller 30 sets the write current in the first target digit area to WC -1 , the write current in the second target digit area is set to WC2, and the write current in the third target digit area is set to WC -2 (S214).

[0105] If the write current in the first target digit area has been set (S203: Yes), or after the processing of S206, S207, S210, S211, S213, or S214, the controller 30 determines whether or not there is a digit area in the first target track that has not yet been selected as a first target digit area (S215). If there is a digit area in the first target track that has not yet been selected as a first target digit area (S215: Yes), the control transitions to S202, and the controller 30 selects any one of the digit areas that has not yet been selected as a first target digit area as a new first target digit area.

[0106] If there is no digit area in the first target track that has not yet been selected as the first target digit area (S215: No), one setting operation unit is completed.

[0107] When "0" is written to the first digit field, WC2 or WC is written to the second digit field. -2When the last track includes a digit area where the value to be written is "0", the controller 30 provides an extra track adjacent to the last track on the opposite side to the first track, and assigns WC2 or WC3 to the extra track. -2 The additional track is written with a write current. Note that in the radial direction, a part or all of the additional track may be included in the guard area 140. However, the additional track is prohibited from extending beyond the boundary of the guard area 140 into the adjacent band area 130.

[0108] 12 is a diagram illustrating an example of a write operation to an additional track in the first embodiment. In this diagram, track #m is the last track in a certain band area 130, and track #m-1 is track 41, which is immediately before track #m in the write order.

[0109] In track #m, "0" is written in digit areas D10, D12, and D14. Therefore, in order to make each of the digit areas D10, D12, and D14 a state in which the polarity of a part of the digit area is inverted, the controller 30 provides an additional track adjacent to track #m, and writes WC2 or WC3 in digit areas D11, D13, and D15 of the additional track. -2 Write is performed using a write current of .

[0110] 12, a pre-setting is made so that writing is performed using a write current of WC2 for the additional tracks. Therefore, the controller 30 sets the write currents for the digit areas D10, D12, and D14 as negative write currents in accordance with this pre-setting. Then, the controller 30 performs writing using a write current of WC2 for the digit areas D11, D13, and D15.

[0111] The method of setting the write current when writing to the additional track is not limited to the above.

[0112] When writing "1" or "-1" to the digit area of ​​track #m, the controller 30 magnetizes the destination digit area to either positive or negative polarity depending on the value to be written. After magnetizing the destination digit area to either positive or negative polarity, the controller 30 refrains from magnetizing digit areas adjacent to the destination digit area in the additional track.

[0113] In the description of the first embodiment, the operation of magnetizing the first digit area while suppressing the influence on the magnetization of the third digit area, WC1 or WC -1 The operation of magnetizing the first digit area using the write current of is an example of a first magnetization operation. -1 The radial recording width of the magnetic head 22 when this write current is supplied is an example of the first recording width.

[0114] WC2 or WC, which is the operation of magnetizing the first digit area while reversing the magnetization of a portion of the third digit area. -2 The operation of magnetizing using the write current of is an example of the second magnetization operation. -2 The radial recording width of the magnetic head 22 when this write current is supplied is an example of the second recording width.

[0115] "1" is an example of a first value, and "-1" is an example of a second value. "0" is an example of a third value that is different from both the first and second values. Positive polarity is an example of a first polarity. Negative polarity is an example of a second polarity. An operation of writing "1" to the first digit area is an example of a first write operation. An operation of writing "-1" to the first digit area is an example of a second write operation. An operation of writing "0" to the first digit area is an example of a third write operation.

[0116] As described above, the magnetic disk device 1 of the first embodiment has the following features. That is, the magnetic head 22 can perform a magnetization operation on the magnetic disk 11 to magnetize it to either positive or negative polarity. The magnetization operation includes a first magnetization operation to magnetize the magnetic disk 11 with a first recording width and a second magnetization operation to magnetize the magnetic disk 11 with a second recording width larger than the first recording width. The controller 30 can perform any of the following write operations: an operation to write "1" to the first digit area (i.e., a first write operation), an operation to write "-1" to the first digit area (i.e., a second write operation), and an operation to write "0" to the first digit area (i.e., a third write operation). In the first write operation, the controller 30 magnetizes the first digit area to positive polarity in the first magnetization operation or the second magnetization operation. In the second write operation, the controller 30 magnetizes the first digit area to a negative polarity in the first or second magnetization operation, and in the third write operation, the controller 30 magnetizes the first digit area to a positive or negative polarity in the first or second magnetization operation, and then magnetizes the second digit area to a polarity opposite to that of the first digit area in the second magnetization operation.

[0117] Therefore, a value that can take three levels is written per digit area. In other words, data is written to the magnetic disk 11 as information expressed in ternary notation. This allows for a larger storage capacity than the magnetic disk device according to the comparative example without increasing the number of digit areas.

[0118] Furthermore, according to the first embodiment, in the third write operation, the controller 30 magnetizes the second digit area in the second magnetization operation, thereby reversing the magnetization of part of the first digit area.

[0119] Therefore, the first digit area can be in three states: a state where the entire area is magnetized with a positive polarity, a state where the entire area is magnetized with a negative polarity, or a state where a portion of the area is magnetized with a positive polarity and the rest is magnetized with a negative polarity. This allows values ​​that can take three levels to be written per digit area.

[0120] According to the first embodiment, in the third write operation, the controller 30 specifies the direction of the write current to be used in the second digit area, i.e., the polarity of the second digit area, by specifying the value to be written in the second digit area. Then, the controller 30 magnetizes the second digit area to a polarity opposite to that of the second digit area.

[0121] Furthermore, according to the first embodiment, if the value written to the third digit area is "1" or "-1", the controller 30 magnetizes the first digit area with the first magnetization operation. If the value written to the third digit area is "0", the controller 30 magnetizes the first digit area with the second magnetization operation.

[0122] Therefore, the third digit area can be in three states: a state in which the entire area is magnetized in positive polarity, a state in which the entire area is magnetized in negative polarity, or a state in which a portion of the area is magnetized in one of the positive and negative polarities and the remainder is magnetized in the other of the positive and negative polarities. This allows values ​​that can take three levels to be written per digit area.

[0123] Also, according to the first embodiment, in the first write operation, the first digit area is magnetized to positive polarity by the first magnetization operation or the second magnetization operation, and then the second digit area is magnetized to positive polarity or negative polarity by the first magnetization operation. In the second write operation, the first digit area is magnetized to negative polarity by the first magnetization operation or the second magnetization operation, and then the second digit area is magnetized to positive polarity or negative polarity by the first magnetization operation.

[0124] Therefore, the first digit area is either entirely magnetized with positive polarity or entirely magnetized with negative polarity.

[0125] Furthermore, according to the first embodiment, writing is performed in one direction on a track 41-by-track basis on the multiple tracks 41 included in one band area 130 from the first track to the last track. As described with reference to FIG. 12 , the controller 30 can perform an operation (referred to as a fourth write operation) to write “0” to one digit area (referred to as a fourth digit area) included in the last track. In the fourth write operation, the controller 30 magnetizes the fourth digit area to either positive or negative polarity in the first magnetization operation or the second magnetization operation, and then magnetizes a fifth digit area included in the additional track to the polarity opposite to that of the fourth digit area in the second magnetization operation of the fourth digit area. The fifth digit area is a digit area adjacent to the fourth digit area.

[0126] Also, according to the first embodiment, as shown in Fig. 12, the controller 30 can execute an operation (referred to as a fifth write operation) of writing "1" or "-1" to the fourth digit area. In the fifth write operation, the controller 30 magnetizes the fourth digit area to a positive polarity or a negative polarity by a first magnetization operation or a second magnetization operation, and then refrains from magnetizing the fifth digit area included in the additional track.

[0127] Also, according to the first embodiment, in the first magnetization operation, the controller 30 causes the magnetic head 22 to -1 In the second magnetization operation, the controller 30 supplies the magnetic head 22 with a write current of WC2 or WC3, which is larger than that in the first magnetization operation. -2 supplies a write current of

[0128] Therefore, in the second magnetization operation, it is possible to perform magnetization with a larger recording width than in the first magnetization operation.

[0129] (Second embodiment) In the second embodiment, an example of an operation in which the controller 30 generates write data expressed in ternary notation will be described. Here, the explanation will be given assuming that K=2. Note that the operation described in the second embodiment is executed, for example, in S101 of FIG. 10.

[0130] The controller 30 receives data expressed in binary numbers from the host 2. The controller 30 generates write data expressed in ternary numbers by converting the received data. The operation of converting the binary number data to ternary number data is performed, for example, in the RWC 25. Note that this conversion operation may also be performed in a circuit other than the RWC 25.

[0131] FIG. 13 is a diagram illustrating an example of a write data generation method executed by the controller 30 of the second embodiment.

[0132] The controller 30 converts three-digit information expressed in binary into two-digit information expressed in ternary. The three-digit information expressed in binary can have eight different values. The two-digit information expressed in ternary can have nine different values. The controller 30 assigns a one-to-one correspondence between the eight possible values ​​of the three-digit information expressed in binary and the eight possible values ​​of the two-digit information expressed in ternary, excluding "00." Then, the controller 30 generates two-digit information expressed in ternary based on this correspondence.

[0133] The controller 30 sets the value of the first digit of the generated two-digit information expressed in ternary as the write data for a certain track 41 (for example, track #p), and sets the value of the second digit of the two-digit information as the write data for a track 41 adjacent to track #p (i.e., track #p+1).

[0134] Since the two-digit information expressed in ternary does not include "00," the write data generated as described above can satisfy the constraint that the number of digit areas in which consecutive "0"s are written in the radial direction is two or less.

[0135] (Third embodiment) When the polarity of a portion of the third digit area is inverted by a write operation to the first digit area, by controlling the ratio of the inverted portion to the third digit area, it is possible to further control the third level of the signal level obtained from the third digit area to multiple levels in a read operation. In other words, a value that can take four or more levels can be written per digit area.

[0136] In the third embodiment, a technology that enables writing values ​​that can take four levels per digit area will be described. Note that in the third embodiment, differences from the first embodiment will be described. Explanations of the same matters as in the first embodiment will be omitted or will be explained briefly.

[0137] FIG. 14 is a diagram for explaining a method for writing a value that can take on four levels according to the third embodiment.

[0138] In the example shown in FIG. 14, the values ​​written to one digit area can be "-1", "-0.3", "0.3", or "1". "1" is associated with a state in which the entire digit area is positive polarity. "0.3" is associated with a state in which approximately 2 / 3 of the digit area is positive polarity. "-0.3" is associated with a state in which approximately 1 / 3 of the digit area is positive polarity. "-1" is associated with a state in which the entire digit area is negative polarity.

[0139] The controller 30 controls the amount of write current supplied to the magnetic head 22 to WCa3, WCa2, ​​WCa1, WCa -1 , WCa -2 , and WCa -3 WCa1, WCa2, ​​and WCa3 are positive write currents. The current amount of WCa3 is greater than that of WCa2, ​​and the current amount of WCa2 is greater than that of WCa1. WCa -1 , WCa -2 , and WCa-3 is the negative write current. WCa -3 The current amount of WCa is approximately equal to the current amount of WCa -2 The current amount of WCa is approximately equal to the current amount of WCa2, -1 The current amount of WCa1 is approximately equal to the current amount of WCa1.

[0140] When a write current of WCa1 is supplied, the recording width in the radial direction by the magnetic head 22 is WCa -1 The radial recording width of the magnetic head 22 when a write current of WCa2 is supplied is approximately equal to WCa -2 The radial recording width of the magnetic head 22 when a write current of WCa3 is supplied is approximately equal to WCa -3 This is approximately equal to the radial recording width of the magnetic head 22 when a write current of 100 .mu.m is supplied.

[0141] As long as the same recording width is obtained, Wca -3 The current amount of WCa3 does not have to be equal to the current amount of WCa3. -2 The current amount of WCa2 does not have to be equal to the current amount of WCa2. -1 The current amount of WCa1 does not have to be equal to the current amount of WCa1.

[0142] Also, WCa2 or WCa -2 When a write current of WCa1 is supplied, the recording width in the radial direction by the magnetic head 22 is WCa1 or WCa -1 WCa3 or WCa -3 When a write current of WCa2 is supplied, the recording width in the radial direction by the magnetic head 22 is WCa2 or WCa -2 is larger than the radial recording width of the magnetic head 22 when a write current of .gtoreq.1 is supplied.

[0143] Specifically, WCa1 or WCa -1The radial recording width of the magnetic head 22 when the write current WCa2 or WCa is supplied is a recording width that can minimize the influence on the magnetism of the third digit area. -2 The radial recording width of the magnetic head 22 when a write current of WCa3 or WCa is supplied is a recording width that can magnetize approximately one-third of the third digit area. -3 The recording width in the radial direction by the magnetic head 22 when a write current of this magnitude is supplied is a recording width that can magnetize approximately two-thirds of the third digit area.

[0144] As in the first embodiment, the direction and amount of the write current in the first digit area are set based on the value written to the first digit area, the direction of the write current in the second digit area (in other words, the value written to the second digit area), and the value written to the third digit area.

[0145] For example, the value written to digit area D20 is "-0.3." If digit area D20 is considered to be the first digit area, digit area D21 corresponds to the second digit area. Since the value written to digit area D21 is "-1," a negative write current is used in digit area D21. Therefore, a positive write current is used in digit area D20.

[0146] When the digit area D21 is regarded as the first digit area, the digit area D20 corresponds to the third digit area. Under the condition that a positive write current is used in the digit area D20 and a negative write current is used in the digit area D21, in order to set the digit area D20 in a state where approximately one-third of the area of ​​the digit area D20 is positive, that is, a state corresponding to "-0.3", the controller 30 sets the digit area D21 to a state where WCa -3 Use a write current of

[0147] For example, the value written to the digit area D22 is "-0.3." Since the value written to the digit area D23 is "1," a positive write current is used in the digit area D23. Therefore, a negative write current is used in the digit area D22.

[0148] Under the condition that a negative write current is used in digit area D22 and a positive write current is used in digit area D23, the controller 30 uses a write current of WCa2 in digit area D23 to set digit area D22 to a state in which approximately 1 / 3 of digit area D22 is positive, i.e., a state corresponding to "-0.3".

[0149] In the third embodiment, the operation of writing "1" to the first digit area is an example of a first write operation. The operation of writing "-1" to the first digit area is an example of a second write operation. The operation of writing "0.3" to the first digit area and the operation of writing "-0.3" to the first digit area are both examples of a third write operation.

[0150] That is, in the third embodiment, the controller 30 can write values ​​that can take two levels per digit area by varying the proportion of the portion where the magnetization in the digit area is reversed depending on whether the value to be written is "0.3" or "-0.3" in the third write operation. That is, by the first write operation, second write operation, and third write operation, it is possible to write values ​​that can take four levels in total per digit area.

[0151] In addition, in the third write operation, the controller 30 can write a value that can take on three or more levels per digit area by varying the proportion of the portion where the magnetization in the digit area is reversed by three or more. In other words, it becomes possible to write a value that can take on five or more levels in total per digit area by the first write operation, second write operation, and third write operation.

[0152] (Fourth embodiment) In the first to third embodiments, the recording width is controlled by controlling the magnitude of the write current supplied to the magnetic head 22. The method for controlling the recording width is not limited to the method using control of the magnitude of the write current supplied to the magnetic head 22.

[0153] Energy-assisted recording is a well-known method for magnetizing a magnetic disk. Energy-assisted recording applies some kind of energy to the magnetic disk, making it possible to magnetize the magnetic disk even with a small write current.

[0154] The energy-assisted recording method includes a microwave-assisted magnetic recording (MAMR) method and a heat-assisted magnetic recording (HAMR) method.

[0155] In microwave-assisted magnetic recording, microwaves are applied to the magnetic disk, reducing the magnetic field required for magnetization of the magnetic disk. In thermally assisted magnetic recording, near-field light or other light is used to locally heat the magnetic disk, reducing the coercivity of the magnetic disk.

[0156] When the energy-assisted recording method is adopted, the controller 30 can control the recording width by controlling the amount of assistance by microwaves, heat, etc. (hereinafter referred to as the energy assist amount). The controller 30 can increase the recording width as the energy assist amount increases.

[0157] In the fourth embodiment, the magnetic head 22 includes an assist element that can apply energy to the magnetic disk 11. The assist element is an element that generates microwaves or near-field light. The controller 30 controls the amount of energy assist, i.e., the intensity of the microwaves or near-field light generated by the assist element.

[0158] FIG. 15 is a diagram for explaining an example of a method for controlling the print width according to the fourth embodiment.

[0159] 15, part (A) shows the write data of track #n and track #n+1, part (B) shows the waveform of the write current, and part (C) shows the waveform of the energy assist amount. The write data of track #n and track #n+1 shown in part (A) is the same as the write data of track #n and track #n+1 shown in parts (A) of FIGS.

[0160] As shown in FIG. 15, the controller 30 controls the magnitude of the write current supplied to the magnetic head 22 by controlling the WCb1 and WCb -1 WCb1 is the positive write current. -1 is the negative write current. -1 The current amount of WCb1 is equal to the current amount of WCb2.

[0161] Furthermore, the controller 30 can control the amount of energy assist to EA1 and EA2.

[0162] WCb1 or WCb -1When the energy assist of EA1 is performed while the write current of WCb1 or WCb2 is supplied to the magnetic head 22, the radial recording width of the magnetic head 22 is a recording width that can minimize the influence on the magnetism of the third digit area. -1 When the energy assist of EA2 is performed while the write current of WCb1 or WCb2 is being supplied, the radial recording width of the magnetic head 22 is set to a level that can magnetize approximately half of the third digit area. -1 When the energy assist of EA2 is performed while the write current of WCb1 is being supplied, the recording width in the radial direction by the magnetic head 22 is -1 1. This is larger than the radial recording width of the magnetic head 22 when the energy assist of EA1 is performed while the write current of EA1 is being supplied.

[0163] The controller 30 sets the direction of the write current in the same manner as in the first embodiment. However, instead of controlling the amount of the write current in multiple stages, the controller 30 controls the amount of energy assist in multiple stages. Specifically, the controller 30 controls the write current in the direction of WC1 or WC2. -1 The controller 30 sets the energy assist amount to EA1 instead of setting the write current to WC2 or WC -2 7C, the amount of energy assist is set to EA2. This makes it possible to realize the same magnetization state as the magnetization state shown in part (C) of FIG.

[0164] That is, in the fourth embodiment, the operation of magnetizing while applying energy EA1 by the assist element corresponds to the first magnetization operation of magnetizing at the first recording width, and the operation of magnetizing while applying energy EA2 greater than EA2 by the assist element corresponds to the second magnetization operation of magnetizing at the second recording width.

[0165] Thus, according to the fourth embodiment, the controller 30 provides energy EA1 by the assist element in the first magnetization operation, and provides energy EA2, which is greater than EA1, by the assist element in the second magnetization operation.

[0166] Therefore, by controlling the amount of energy given from the assist element to the magnetic disk 11 in multiple stages, it is possible to write values ​​that can take three levels per digit area. This makes it possible to increase the storage capacity without increasing the number of digit areas compared to the magnetic disk device according to the comparative example.

[0167] In the fourth embodiment, the energy assist amount is controlled to two levels, EA1 and EA2. The energy assist amount may be controlled to three or more levels. By controlling the energy assist amount to three or more levels, it becomes possible to write a value that can take four or more levels per digit area, as in the third embodiment, for example.

[0168] According to the first, second, third, and fourth embodiments, the controller 30 performs the above-described operations, and as a result, the multiple digit areas of the magnetic disk 11 include the following digit areas. That is, the multiple digit areas include a digit area that is entirely magnetized with positive polarity by the magnetic head 22. The multiple digit areas include a digit area that is entirely magnetized with negative polarity by the magnetic head 22. The multiple digit areas include a digit area that is partly magnetized in the radial direction with one of positive and negative polarity by the magnetic head 22, and the remainder is magnetized with the other of positive and negative polarity.

[0169] Furthermore, according to the first, second, third, and fourth embodiments, the boundary between the digit areas in the circumferential direction is aligned between a first track and a second track adjacent to the first track, which allows a part of the digit area in the radial direction to be magnetized with one of the positive and negative polarities, and the rest to be magnetized with the other of the positive and negative polarities.

[0170] Furthermore, according to the first, second, third, and fourth embodiments, the number of digit areas in which the polarity of some areas is inverted arranged in the radial direction is limited to a predetermined number (K ​​in the above example), where K is 2, for example.

[0171] Furthermore, according to the first embodiment, when the polarity of a portion of each of the multiple digit areas is inverted, the ratio R of the inverted portion to the digit area is uniform across the multiple digit areas. Specifically, the ratio R is approximately 0.5.

[0172] According to the third embodiment, when the polarity of a portion of each of a plurality of digit areas is inverted, the ratio R of the inverted portion to the digit area is a first value or a second value. The first value is, for example, 0.3, and the second value is, for example, 0.7 (=1-0.3).

[0173] 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]

[0174] 1 magnetic disk device, 2 host, 11 magnetic disk, 12 spindle motor, 13 ramp, 15 actuator arm, 16 voice coil motor, 22 magnetic head, 22r read element, 22w write element, 23 HDC, 24 head IC, 25 RWC, 26 processor, 27 RAM, 28 FROM, 29 buffer memory, 30 controller, 41 track, 42 ​​servo area, 43 data area, 100 recording surface, 110 storage area, 120 media cache area, 130 band area, 140 guard area.

Claims

1. a magnetic disk having a plurality of tracks, each of the plurality of tracks including a plurality of area units arranged along the track; a magnetic head that executes a magnetization operation to magnetize the magnetic disk to either a first polarity or a second polarity that is opposite to the first polarity, the magnetization operation including a first magnetization operation to magnetize the magnetic disk with a first recording width and a second magnetization operation to magnetize the magnetic disk with a second recording width that is larger than the first recording width; any of the following write operations can be executed: a first write operation for writing a first value to a first area unit, which is an area unit included in a first track, which is one of the plurality of tracks; a second write operation for writing a second value different from the first value to the first area unit; and a third write operation for writing a third value different from both the first value and the second value to the first area unit; In the first write operation, the first area unit is magnetized to the first polarity in the first magnetization operation or the second magnetization operation; In the second write operation, the first area unit is magnetized to the second polarity in the first magnetization operation or the second magnetization operation; In the third write operation, the first area unit is magnetized to either the first polarity or the second polarity in the first magnetization operation or the second magnetization operation, and then the second area unit is magnetized to a polarity opposite to that of the first area unit in the second magnetization operation, and the second area unit is an area unit radially adjacent to the first area unit included in a second track that is a track adjacent to the first track among the plurality of tracks and is a track to be written after the first track. A controller; A magnetic disk device comprising:

2. In the third write operation, the controller: The second area unit is magnetized by the second magnetization operation, thereby reversing the magnetization of a part of the first area unit.

2. The magnetic disk drive according to claim 1.

3. the controller, in the third write operation, specifies the polarity of the second area unit and magnetizes the first area unit to a polarity opposite to the specified polarity of the second area unit; 2. The magnetic disk drive according to claim 1.

4. The controller, in the first write operation, the second write operation, and the third write operation, When the value to be written in a third area unit is the first value or the second value, the first area unit is magnetized by the first magnetization operation, and the third area unit is an area unit radially adjacent to the first area unit included in a third track, which is a track adjacent to the first track among the plurality of tracks and is written before the first track; If the value written to the third area unit is the third value, the first area unit is magnetized by the second magnetization operation.

2. The magnetic disk drive according to claim 1.

5. The controller In the first write operation, the first area unit is magnetized to the first polarity in the first magnetization operation or the second magnetization operation, and then the second area unit is magnetized to either the first polarity or the second polarity in the first magnetization operation; in the second write operation, after magnetizing the first area unit to the second polarity in the first magnetization operation or the second magnetization operation, magnetizing the second area unit to either the first polarity or the second polarity in the first magnetization operation; 2. The magnetic disk drive according to claim 1.

6. The controller writing is performed on a plurality of radially consecutive fourth tracks among the plurality of tracks using an SMR (Shingled Magnetic Recording) method, and the order of writing on the plurality of fourth tracks in track units is from a fifth track, which is a fourth track at one end in the radial direction of the plurality of fourth tracks, to a sixth track, which is a fourth track at the other end in the radial direction of the plurality of fourth tracks; a fourth write operation can be executed to write the third value to a fourth area unit that is one area unit included in the sixth track; In the fourth write operation, the fourth area unit is magnetized to either the first polarity or the second polarity in the first magnetization operation or the second magnetization operation, and then a fifth area unit is magnetized to a polarity opposite to that of the fourth area unit in the second magnetization operation, and the fifth area unit is an area unit radially adjacent to the fourth area unit and included in a track opposite to the side facing the fifth track, of two tracks adjacent to the sixth track.

2. The magnetic disk drive according to claim 1.

7. The controller a fifth write operation is executable to write the first value or the second value to the fourth area unit; In the fifth write operation, the fourth area unit is magnetized to the first polarity or the second polarity in the first magnetization operation or the second magnetization operation, and then the magnetization of the fifth area unit is refrained from.

7. The magnetic disk drive according to claim 6.

8. The controller supplying a first amount of write current to the magnetic head in the first magnetizing operation; supplying a second amount of write current, which is greater than the first amount, to the magnetic head in the second magnetizing operation; 8. The magnetic disk drive according to claim 1.

9. the magnetic head includes an assist element that applies energy to the magnetic disk; The controller In the first magnetization operation, a third amount of energy is applied to the magnetic disk by the assist element; In the second magnetization operation, a fourth amount of energy greater than the third amount is applied to the magnetic disk by the assist element.

8. The magnetic disk drive according to claim 1.

10. the third value includes a plurality of fourth values ​​that are different from each other; the controller, in the third write operation, varies a ratio of a portion of the first area unit where magnetization is reversed to the first area unit for each of the plurality of fourth values; 2. The magnetic disk drive according to claim 1.

11. a magnetic disk having a plurality of tracks, each of the plurality of tracks including a plurality of area units arranged along the track; a magnetic head for magnetizing the magnetic disk; Equipped with The plurality of area units are a first area unit that is entirely magnetized to a first polarity by the magnetic head; a second area unit magnetized as a whole to a second polarity opposite to the first polarity; a third area unit, a part of which in the radial direction is magnetized by the magnetic head with one of the first polarity and the second polarity, and the remainder of which is inverted with the other of the first polarity and the second polarity; Including, Magnetic disk device.

12. a boundary between the plurality of area units included in a first track, which is one of the plurality of tracks, and a boundary between the plurality of area units included in a second track, which is one of the plurality of tracks adjacent to the first track, are aligned; The magnetic disk drive according to claim 11.

13. The number of the third area units arranged in the radial direction is limited to 2 or less. The magnetic disk drive according to claim 11.

14. 12. The magnetic disk device of claim 11, wherein the plurality of area units include a plurality of fourth area units corresponding to the third area units, and the ratio of the portions of the area units that are inverted by the other polarity in the radial direction is uniform among the plurality of area units.

15. 15. The magnetic disk drive according to claim 14, wherein the ratio is 0.

5.

16. the plurality of area units include a plurality of fourth area units corresponding to the third area units, and in each of the plurality of area units, a ratio of a portion of the area unit inverted by the other polarity in the radial direction is a first value or a second value; The magnetic disk drive according to claim 11.

17. the first value is 0.3 and the second value is 0.7; 17. The magnetic disk drive according to claim 16.

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