Magnetic disk device

Abstract

The invention provides a magnetic disk device having a large storage capacity. The magnetic head performs a magnetization operation that magnetizes the magnetic disk to either a first polarity or a second polarity opposite to the first polarity. The magnetization operation includes a first magnetization operation in which magnetization is performed with a first recording width and a second magnetization operation in which magnetization is performed with a second recording width larger than the first recording width. The controller magnetizes the first region unit to a first polarity or a second polarity by a first magnetization operation or a second magnetization operation, and thereafter magnetizes the second region unit to a polarity opposite to that of the first region unit by the second magnetization operation. The second region unit is included in a second track, which is a track that is adjacent to the first track and is written after the first track, among the plurality of tracks, and is adjacent to the first region unit in the radial direction.

Description

[0001] This application claims the benefit of priority based on Japanese Patent Application No. 2024-045267 (filing date: March 21, 2024), the entire contents of which are incorporated herein by reference. Technical Field

[0002] An embodiment of the present invention relates to a magnetic disk device. Background Art

[0003] Conventionally, data represented in binary format is written to a magnetic disk in a magnetic disk device. Summary of the Invention

[0004] An embodiment of the present invention provides a magnetic disk device with a large storage capacity.

[0005] A magnetic disk device according to an embodiment includes a magnetic disk, a magnetic head, and a controller. The magnetic disk is provided with multiple tracks, each of which includes multiple regional units arranged along the tracks. The magnetic head performs a magnetizing operation on the magnetic disk to either a first polarity or a second polarity opposite to the first polarity. The magnetizing operation includes a first magnetizing operation of magnetizing with a first recording width and a second magnetizing operation of magnetizing with a second recording width larger than the first recording width. The controller can perform any one of a first write operation of writing a first value to the first regional unit, a second write operation of writing a second value to the first regional unit, and a third write operation of writing a third value to the first regional unit. The first regional unit is a regional unit included in the first track, which is one of the multiple tracks. The second value is a value different from the first value. The third value is a value different from either the first value or the second value. In the first write operation, the controller magnetizes the first regional unit to the first polarity using either the first magnetizing operation or the second magnetizing operation. In the second write operation, the controller magnetizes the first regional unit to the second polarity using the first magnetization operation or the second magnetization operation. In the third write operation, the controller magnetizes the first regional unit to either the first polarity or the second polarity using the first magnetization operation or the second magnetization operation, and then magnetizes the second regional unit to the opposite polarity of the first regional unit using the second magnetization operation. The second regional unit is a regional unit radially adjacent to the first regional unit and included in a second track, which is a track adjacent to the first track and to be written after the first track, among the plurality of tracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 This is a schematic diagram showing an example of the configuration of the magnetic disk device according to the first embodiment.

[0007] Figure 2 This is a schematic diagram showing an example of the structure of the magnetic disk according to the first embodiment.

[0008] Figure 3 This is a schematic diagram for explaining the SMR method used in the magnetic disk device according to the first embodiment.

[0009] Figure 4 This is a diagram showing an example of a plurality of band areas provided on a magnetic disk according to an embodiment.

[0010] Figure 5 This is another diagram showing an example of a plurality of band areas provided on the magnetic disk according to the embodiment.

[0011] Figure 6 (A) to (C) are diagrams for explaining a method of writing ternary information according to the first embodiment.

[0012] Figure 7 (A) to (C) are other diagrams for explaining the method of writing ternary information according to the first embodiment.

[0013] Figure 8 (A) to (C) are still another diagram for explaining the method of writing ternary information according to the first embodiment.

[0014] Figure 9 This is a diagram showing an overview of setting patterns of write currents in two digit areas adjacent to each other in the radial direction in the first embodiment.

[0015] Figure 10 This is a diagram showing an example of a write operation of the magnetic disk device according to the first embodiment.

[0016] Figure 11 This is a flowchart showing an example of the operation of setting the write current in the first embodiment.

[0017] Figure 12 This is a diagram for explaining an example of a write operation to an additional track according to the first embodiment.

[0018] Figure 13 This is a diagram for explaining an example of a method for generating write data executed by the controller according to the second embodiment.

[0019] Figure 14 (A) to (C) are diagrams for explaining a method of writing a value that can take four levels according to the third embodiment.

[0020] Figure 15 (A) to (C) are diagrams for explaining an example of a recording width control method according to the fourth embodiment.

[0021] Description of labels

[0022] 1 Magnetic disk device, 2 Host, 11 Magnetic disk, 12 Spindle motor, 13 Ramp, 15 Actuator arm, 16 Voice coil motor, 22 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 Tape area, 140 Guard area. DETAILED DESCRIPTION

[0023] Hereinafter, the magnetic disk device according to the embodiment will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments.

[0024] (First embodiment)

[0025] Figure 1 This is a schematic diagram showing an example of the configuration of the magnetic disk device 1 according to the first embodiment.

[0026] The magnetic disk device 1 is connected to a host computer 2. The magnetic disk device 1 can receive access commands such as a write command and a read command from the host computer 2.

[0027] 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 access commands. While the magnetic disk device 1 may include multiple magnetic disks 11, in the embodiments, for simplicity of description and illustration, the magnetic disk device 1 is assumed to include a single magnetic disk 11.

[0028] Data is written and read via the magnetic head 22. Specifically, the magnetic disk device 1 includes, in addition to the 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, a RAM 27, a FROM (Flash Read Only Memory) 28, a buffer memory 29, a hard disk controller (HDC) 23, and a processor 26.

[0029] The magnetic disk 11 is rotated at a predetermined rotation speed by a spindle motor 12 attached to a rotation shaft of the magnetic disk 11. The spindle motor 12 is driven by a motor driver IC 21.

[0030] The motor driver IC 21 controls the rotation of the spindle motor 12 and the rotation of the VCM 16 .

[0031] The magnetic head 22 writes data to and reads data from the magnetic disk 11 using its write element 22w and read element 22r. The magnetic head 22 is mounted on the front end of the actuator arm 15. The magnetic head 22 moves radially of the magnetic disk 11 via the VCM 16 driven by the motor driver IC 21.

[0032] When the rotation of the magnetic disk 11 stops, the magnetic head 22 moves onto the ramp 13 . The ramp 13 is configured to hold the magnetic head 22 at a position separated from the magnetic disk 11 .

[0033] During reading, the head IC 24 amplifies the signal read by the magnetic head 22 from the magnetic disk 11 , outputs the amplified signal, and supplies it to the RWC 25 . Furthermore, the head IC 24 amplifies the signal corresponding to the write target data supplied from the RWC 25 , and supplies the amplified signal to the magnetic head 22 .

[0034] The HDC 23 controls data transmission and reception with the host computer 2 via the I / F bus, controls the buffer memory 29 , and performs error correction processing on read data.

[0035] The buffer memory 29 is used as a buffer for data transmitted and received with 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 to be read from the magnetic disk 11.

[0036] The buffer memory 29 is composed of, for example, a volatile memory capable of high-speed operation. The type of memory constituting the buffer memory 29 is not limited to a specific type. The buffer memory 29 can be composed of, for example, DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), or a combination thereof.

[0037] The RWC 25 modulates the data to be written supplied from the HDC 23 and supplies the modulated data to the head IC 24. The RWC 25 also demodulates the signal read from the magnetic disk 11 and supplied from the head IC 24, and outputs the demodulated signal to the HDC 23 as digital data.

[0038] 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 .

[0039] The FROM 28 is a nonvolatile memory. Firmware (program data) and various operating parameters are stored in the FROM 28. Alternatively, the firmware may be stored in the magnetic disk 11.

[0040] The RAM 27 is composed of, for example, a DRAM, an SRAM, or a combination thereof. The RAM 27 is used as an operation memory by the processor 26. The RAM 27 is used as an area for loading firmware and / or an area for storing various management data.

[0041] The processor 26 controls the entire magnetic disk device 1 according to the firmware stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads the firmware from the FROM 28 or the magnetic disk 11 into the RAM 27 and controls the motor driver IC 21, the head IC 24, the RWC 25, the HDC 23, and the like according to the loaded firmware.

[0042] Furthermore, the configuration including the RWC 25, processor 26, and HDC 23 can also be considered as the controller 30. The controller 30 is sometimes configured as a SoC (System-On-a-Chip). The controller 30 does not necessarily need to be configured as a SoC. The controller 30 may also include other elements (e.g., RAM 27, FROM 28, buffer memory 29, or RWC 25).

[0043] Figure 2 This 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 rotational 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 direction in which data is written or read by the magnetic head 22, which is along the write / read direction, i.e., the circumferential direction, is opposite to the rotational direction of the magnetic disk 11.

[0044] Servo information is written to the magnetic disk 11 during the manufacturing process, for example, by a servo writer or self-servo writing (SSW). Figure 2 As an example of the arrangement of the servo areas in which the servo information is written, servo areas 42 arranged radially are shown. Between the servo areas 42, data areas 43 in which data can be written are provided.

[0045] A plurality of concentric tracks 41 are set based on servo information in the radial direction of the magnetic disk 11. In a plurality of data areas 43 provided along the tracks 41, a plurality of sectors for data writing are arranged.

[0046] As a method of writing data on a magnetic disk, a method called SMR (Shingled Magnetic Recording) and a method called CMR (Conventional Magnetic Recording) are known.

[0047] Figure 3This is a schematic diagram for explaining 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) is written to a certain track 41 and then data (referred to as second data) is written to a track 41 radially adjacent to the track 41, 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 from one track 41 of two radially adjacent tracks 41 on the magnetic disk 11 is written so that the data overlaps a portion of the data from the other track 41.

[0048] For example, data on track #2 is written so as to overlap a portion of the data already written on track #1. Furthermore, data on track #3 is written so as to overlap a portion of the data already written on track #2. In other words, with the SMR method, the data on one track overlaps a portion of the data already written on the adjacent track repeatedly.

[0049] As a result, each track width TW is narrowed compared to the width (WHw) of the write element 22w, thereby improving the recording density.

[0050] However, in the SMR method, since the track width TW is narrower than the width WHw of the write element 22w, if a portion of data corresponding to multiple tracks is updated, data on adjacent tracks to the updated data is destroyed. To prevent data destruction, data corresponding to multiple tracks containing this portion of data is updated collectively. The area of ​​multiple tracks that are collectively updated is called a band.

[0051] Furthermore, according to the SMR method, it is set that writing can be performed on multiple tracks 41 within one band only from a predetermined one of the outer end and the inner end of the disk toward a predetermined other end. Figure 3 In the example shown, writing is performed from the outer end toward the inner end in units of tracks 41. The controller 30 may also be configured to perform writing from the inner end toward the outer end in units of tracks 41. Furthermore, the order of writing may be set for each band.

[0052] Figure 4 and Figure 5 This is a diagram showing an example of a plurality of band areas provided on the magnetic disk 11 according to the embodiment.

[0053] The recording surface 100 of the magnetic disk 11, i.e., the area where the tracks 41 are arranged, is divided radially into a plurality of storage areas 110. The plurality of storage areas 110 include a media cache area 120 and a plurality of band areas 130. An area called a guard area 140 is provided between the storage areas 110 and cannot be designated as a write destination by the host 2.

[0054] The storage area 110 located at the radially outermost side of the recording surface 100 is designated as a media cache area 120. The media cache area 120 is a storage area used as a temporary storage location for data. The location of the media cache area 120 is not limited to the outermost side. Furthermore, 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 format.

[0055] One or more of the plurality of storage areas 110 is set as a band area 130. Multiple tracks 41 are provided in each band area 130. In each band area 130, data is written to all tracks 41 using the SMR method. When writing data to each band area 130, data is prohibited from being written from the band area 130 designated as the write destination to an adjacent band area 130 across the guard area 140.

[0056] Furthermore, a portion of the plurality of band areas 130 may be configured to write data using the CMR method. The following describes a band area 130 in which data is written using the SMR method.

[0057] When writing to multiple tracks 41 of a 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 recorded 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 recorded as the end track of the band area 130.

[0058] Data can be considered as a column of multiple values. Furthermore, for each sector of track 41, a column of multiple values ​​is written along track 41. In other words, each sector can be considered to have a structure where multiple area units, each capable of holding a single bit value, are arranged in a row along track 41. Each area unit capable of holding a single bit value is referred to as a bit area.

[0059] When a positive write current is supplied to the magnetic head 22, the portion of the recording surface 100 of the magnetic disk 11 where the magnetic head 22 is located can be magnetized to positive polarity. When a negative write current is supplied to the magnetic head 22, the portion of the recording surface 100 of the magnetic disk 11 where the magnetic head 22 is located can be magnetized to negative polarity. The controller 30 controls the write current when the magnetic head 22 passes through each digital area according to the value to be written to each digital area.

[0060] Here, a technique for comparison with the embodiment (hereinafter referred to as a comparative example) is described. According to the comparative example, each digital area can be written to a value with two levels. That is, data is written to the disk as binary information. More specifically, during the write operation, the polarity of the magnetization of the digital area is set to a value corresponding to either positive or negative. During the read operation, based on the signal obtained by the magnetic head, the polarity of the magnetization of the digital area is determined to be positive or negative, and the value corresponding to the determined polarity is obtained.

[0061] In the embodiment, a value that can take three levels is written to each digital area. That is, data is written as ternary information to the magnetic disk 11. This increases the storage capacity compared to the magnetic disk device according to the comparative example without increasing the number of digital areas.

[0062] Figures 6 to 8 This figure is used to illustrate the method of writing ternary information involved in the first embodiment. In the following description, it is assumed that each track 41 is assigned a track number corresponding to the order of arrangement in the radial direction, and writing is performed in the SMR method in units of tracks 41 in the order of the track numbers.

[0063] Here, an example of writing ternary information to three radially continuous tracks, track #n, track #n+1, and track #n+2, is described. Note that data is written to track #n, track #n+1, and track #n+2 in this order.

[0064] In addition, Figure 6 In the following description, it is assumed that the value written to one digital area can be "-1", "0", or "1" associated with different levels. In addition, it is assumed that data written to the magnetic track 41 is described as write data.

[0065] like Figures 6 to 8As shown in part (A), the data written to track #n is a sequence of values ​​such as "-1, 1, 0, -1, 0, 1, 1, -1, 0, 1". The data written to track #n+1 is a sequence of values ​​such as "1, 1, -1, 0, 1, 1, 0, -1, 1, -1". The data written to track #n+2 is a sequence of values ​​such as "-1, -1, -1, 1, 1, -1, -1, -1, 1".

[0066] In addition, the controller 30 can control the write current supplied to the magnetic head 22 to be WC2, WC1, WC -1 and WC -2 WC1 and WC2 are positive write currents, and the current of WC2 is larger than that of WC1. In other words, the current is the absolute value of the amplitude of the current value. -1 and WC -2 is the negative write current, WC -2 The current is greater than WC -1 The current of WC2 is greater than that of WC -2 The current of WC1 is roughly equal to that of WC -1 The currents are roughly equal.

[0067] Alternatively, the current of WC2 may be equal to that of WC -2 The current of WC1 is not equal to that of WC -1 For example, if the characteristics are different due to positive and negative polarity, even if the same current is supplied to the magnetic head 22 with positive and negative polarity, the same recording quality cannot be obtained. In such a case, the current of WC2 is set to be equal to that of WC -2 The current of WC1 is not equal to that of WC -1 In other words, in order to obtain the same recording width, the current of WC2 and WC -2 Similarly, to obtain the same recording width, the current of WC1 and WC -1 The amount of current will be set to different values.

[0068] The radial recording width achieved by the magnetic head 22 when the write current WC1 is supplied is different from the radial recording width achieved when the write current WC1 is supplied. -1 The radial recording width achieved by the magnetic head 22 when the write current of WC2 is supplied is substantially equal to the radial recording width achieved by the magnetic head 22 when the write current of WC2 is supplied. -2 The radial recording width achieved by the magnetic head 22 is substantially equal when the write current is 0. -2The radial recording width achieved by the magnetic head 22 when the write current is supplied is greater than that supplied by WC1 or WC -1 When the write current is large, the recording width in the radial direction achieved by the magnetic head 22 is large.

[0069] like Figure 6 As shown, first, the controller 30 performs 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 digital 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. -1 The write current is applied, thereby magnetizing the digit area at the write destination to negative polarity.

[0070] Here, any three digital regions arranged in the radial direction are referred to as the first digital region, the second digital region, and the third digital region. The second digital region is a digital region that is radially adjacent to the first digital region and included in track 41 that is written after track 41 that includes the first digital region. The third digital region is a digital region that is radially adjacent to the first digital region and included in track 41 that is written before track 41 that includes the first digital region.

[0071] When the value to be written to the first digital area is "0", the controller 30 is set so that the direction of the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the first digital area is opposite to the direction of the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the second digital area.

[0072] Specifically, when the value to be written to the second digital area is "1", the controller 30 makes the write current when the magnetic head 22 passes through the second digital area a positive current. Thus, the controller 30 makes the write current when the magnetic head 22 passes through the first digital area a negative current.

[0073] When the value to be written to the second digit area is "-1", the controller 30 makes the write current when the magnetic head 22 passes through the second digit area a negative current. Thus, the controller 30 makes the write current when the magnetic head 22 passes through the first digit area a positive current.

[0074] For example, the value to be written to the digital area D1 included in track #n is "0". When the digital area D1 is regarded as the first digital area, the digital area D2 included in track #n+1 corresponds to the second digital area. The value to be written to the digital area D2 is "-1", and thus, the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D2 is set to a negative current. Thus, the controller 30 makes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D1 a positive current. Here, the controller 30 supplies a write current of WC1 to the magnetic head 22 in the digital area D1.

[0075] In another example, the value to be written to the digital area D3 included in the track #n is "0". When the digital area D3 is regarded as the first digital area, the digital area D4 included in the track #n+1 corresponds to the second digital area. The value written to the digital area D4 is "1", and thus, the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D4 is set to a positive current. Thus, the controller 30 makes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D3 a negative current. Here, the controller 30 supplies WC to the magnetic head 22 in the digital area D3. -1 The write current

[0076] like Figure 7 As shown, the controller 30 performs a write operation on track #n+1 subsequent to the write operation on track #n.

[0077] In a write operation on 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 write-destination digital region to 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 write-destination digital region to negative polarity.

[0078] When the value written to the first digital area is "1" or "-1", the controller 30 determines the amount of write current supplied to the magnetic head 22 when passing through the first digital area based on whether the value written to the third digital area is "0".

[0079] Specifically, when the value written to the third digital area is "1" or "-1", the controller 30 makes the write current when the magnetic head 22 passes through the first digital area be WC1 or WC -1 When the value written to the third digital area is "0", the controller 30 makes the write current when the magnetic head 22 passes through the first digital area be WC2 or WC -2 .

[0080] As mentioned above, WC2 or WC -2The recording width ratio in the radial direction achieved by the magnetic head 22 when the write current is supplied with WC1 or WC -1 The radial recording width of the magnetic head 22 is large when the write current is 0.1. Therefore, by the write operation to the first digit area, not only the first digit area is magnetized, but also a part of the third digit area is magnetized.

[0081] Moreover, the polarity of the magnetization of the third digital area is set to be opposite to the polarity of the magnetization of the first digital area. Thus, by the writing action on the first digital area, the polarity of a part of the third digital area is reversed. Thus, when the third digital area is read by the magnetic head 22, a signal of a level (referred to as the third level) different from the level obtained when the digital area as a whole is positive polarity (referred to as the first level) and the level obtained when the digital area as a whole is negative polarity (referred to as the second level) can be obtained. In Figures 6 to 8 In the example shown, the first level corresponds to "1", the second level corresponds to "-1", and the third level corresponds to "0".

[0082] For example, the value written to digital area D2 is "-1". When digital area D2 is regarded as the first digital area, digital area D1 included in track #n corresponds to the third digital area. The value written to digital area D1 is "0". Therefore, the controller 30 makes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D2 be WC -2 The controller 30 supplies WC to the magnetic head 22 when the magnetic head 22 passes through the digitizing area D2. -2 The write current inverts the polarity of a radial portion (in this case, half) of the digital region D1 from positive to negative. This magnetization of the digital region D1 is thus adjusted to a state where a third-level signal is obtained during a read operation.

[0083] In other examples, the value written to the digital area D4 is "1". When the digital area D4 is regarded as the first digital area, the digital area D3 included in the track #n corresponds to the third digital area. The value written to the digital area D3 is "0". Thus, the controller 30 causes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D3 to be WC2. The controller 30 causes a portion (here half) of the digital area D3 to be inverted from negative polarity to positive polarity by causing the magnetic head 22 to pass through the digital area D4. Thus, the magnetization state of the digital area D3 is set to a state in which a signal of the third level is obtained in the read operation.

[0084] Thus, the controller 30 determines, based on the three values, whether the magnetization state of the digital region is to be positive, negative, or only a portion of the digital region. Furthermore, during a read operation, the written value is obtained by determining whether the level of the signal received from the magnetic head 22 corresponds to the first, second, or third level. This enables writing / reading of ternary information.

[0085] Similarly, in the write operation in track #n+1 and any other track 41, when the value to be written is "0", the controller 30 makes a decision in such a way that the direction of the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area of ​​the write destination (the first digital area) is opposite to the direction of the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the second digital area.

[0086] For example, the value written to the digital area D5 included in the track #n+1 is "0". When the digital area D5 is regarded as the first digital area, the digital area D6 included in the track #n+2 corresponds to the second digital area. The value written to the digital area D6 is "1", and thus, the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D6 is set to a positive current. Thus, the controller 30 makes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D5 a negative current. Here, the controller 30 supplies WC to the magnetic head 22 in the digital area D5. -1 The write current

[0087] In addition, the value written to the digital area D7 included in the track #n+1 is "0". When the digital area D7 is regarded as the first digital area, the digital area D8 included in the track #n+2 corresponds to the second digital area. The value written to the digital area D8 is "1", and thus, the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D8 is set to a positive current. Thus, the controller 30 makes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D7 a negative current. Here, the controller 30 supplies WC to the magnetic head 22 in the digital area D7. -1 The write current

[0088] like Figure 8 As shown, the controller 30 performs a write operation on track #n+2 subsequent to the write operation on track #n+1.

[0089] Similarly, in the write operation for track #n+2, the direction and amount of the write current in each digital area are set using the same method as for the write operation for tracks #n and #n+1. The direction and amount of the write current in the first digital area are set based on the value written to the first digital area, the polarity of the write current in the second digital area, and the value written to the third digital area.

[0090] For example, the value written to the digital area D6 is "1". When the digital area D6 is regarded as the first digital area, the digital area D5 included in the track #n+1 corresponds to the third digital area. The value written to the digital area D5 is "0". Thus, the controller 30 causes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D6 to be WC2. The controller 30 supplies a write current of WC2 to the magnetic head 22 when the magnetic head 22 passes through the digital area D6, so that a part (here half) of the digital area D5 is inverted from negative polarity to positive polarity. Thus, the magnetization state of the digital area D5 is set to a state in which a signal of the third level is obtained in the read operation.

[0091] In addition, for example, the value written to the digital area D8 is "1". When the digital area D8 is regarded as the first digital area, the digital area D7 included in the track #n+1 corresponds to the third digital area. The value written to the digital area D7 is "0". Thus, the controller 30 causes the write current supplied to the magnetic head 22 when the magnetic head 22 passes through the digital area D8 to be WC2. The controller 30 supplies a write current of WC2 to the magnetic head 22 when the magnetic head 22 passes through the digital area D8, so that a part of the digital area D7 (here half) is inverted from negative polarity to positive polarity. Thus, the magnetization state of the digital area D7 is set to a state in which a signal of the third level is obtained in the read operation.

[0092] Figure 9 This diagram shows an overview of write current setting patterns for two radially adjacent digital areas Da and Db in the first embodiment. It is assumed that digital area Da is included in track #i, and digital area Db is included in track #i+1. Track #i+1 is track 41 to which data is written after track #i.

[0093] like Figure 9 As shown, when the value written to the digital area Da is "1" or "-1", the direction of the write current in the digital area Da is set according to the value written to the digital area Da, regardless of the value written to the digital area Db. When the value written to the digital area Da is "1", the write current in the digital area Da is a positive current. When the value written to the digital area Da is "-1", the write current in the digital area Da is a negative current.

[0094] In the case where the value written to the digital area Da is "0", the direction of the write current in the digital area Da is set according to the direction of the write current in the digital area Db. In the case where the value written to the digital area Da is "0" and the value written to the digital area Db is "1", the write current in the digital area Da is a negative current and the write current in the digital area Db is a positive current. In the case where the value written to the digital area Da is "0" and the value written to the digital area Db is "-1", the write current in the digital area Da is a positive current and the write current in the digital area Db is a negative current. In the case where the value written to the digital area Da is "0" and the value written to the digital area Db is "0", the direction of the write current in the digital areas Da and Db is set according to the direction of the write current in the digital area different from the digital area Da in the two digital areas adjacent to the digital area Db in the radial direction. Figure 9 In FIG, the directions of the write currents in the digital regions Da and Db when the value written to the digital region Da is “0” and the value written to the digital region Db is “0” are shown as undetermined.

[0095] The amount of the write current in the digital area Da is set according to whether the value written to the digital area different from the digital area Db (referred to as the digital area Dc) of the two digital areas adjacent to the digital area Da in the radial direction is "0". When the value written to the digital area Dc is "1" or "-1", the write current in the digital area Da is set to WC1 or WC -1 When the value written to the digital area Dc is "0", the write current in the digital area Da is set to WC2 or WC in order to invert the polarity of a portion of the digital area Dc. -2 .

[0096] Next, the operation of the magnetic disk device 1 according to the first embodiment will be described.

[0097] Figure 10 This is a diagram showing an example of a write operation of the magnetic disk device 1 according to the first embodiment.

[0098] First, the controller 30 prepares write data for a plurality of tracks continuous in the radial direction in the buffer memory 29 ( S101 ).

[0099] The write data prepared in S101 is information expressed in ternary. The controller 30 may also receive binary data from the host 2 and convert the received binary data to generate ternary write data. The write data may also be generated by the RWC 25 included in the controller 30. In that case, the RWC 25 transmits the 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.

[0100] Alternatively, the controller 30 may receive write data expressed in ternary notation from the host 2 and store the received write data in the buffer memory 29 .

[0101] Furthermore, in the case where, for example, p (p is an integer greater than or equal to 2) digital regions to which "0" is written are arranged in the radial direction, if it is uncertain whether the value written to the digital region adjacent to the p digital regions to which "0" is written is "1" or "-1", the direction of the write current in the p digital regions to which "0" is written cannot be set. Thus, an upper limit value for the number of digital regions to which "0" is written continuously in the radial direction is pre-set. This upper limit value is denoted as K (where K is an integer greater than or equal to 2). That is, the write data of the plurality of tracks prepared in the buffer memory 29 in S101 is write data generated under the constraint that the number of digital regions to which "0" is written that are arranged continuously in the radial direction is K or less.

[0102] The controller 30 sets a write current for each bit region based on the write data prepared in the buffer memory 29 ( S102 ).

[0103] The controller 30 writes the write data prepared in the buffer memory 29 to the magnetic disk 11 (S103). In S103, the controller 30 executes writing using the set write current.

[0104] After S103 , the writing operation is completed.

[0105] Figure 11 This is a flowchart showing an example of the operation of setting the write current in the first embodiment. Figure 10 Here, the operation of setting the write current for all digital areas included in one track 41 (the first target track described later) will be described. The series of operations shown in this figure is referred to as a setting operation unit.

[0106] First, the controller 30 selects K+1 radially continuous tracks 41 from among the multiple tracks to which write data is prepared in the buffer memory 29 (S201). Here, K is assumed to be 2. That is, the controller 30 selects three radially continuous tracks 41. Of the three selected tracks 41, the track 41 to which data is written first is designated as the first target track, the track 41 to which data is written second is designated as the second target track, and the track 41 to which data is written last is designated as the third target track.

[0107] Furthermore, a single setting operation unit sets the write current for all digital areas included in the first target track. The setting operation unit is repeatedly executed to set the write current for all digital areas included in all tracks 41 included in one band area 130. The controller 30 changes the selected K+1 tracks 41 by one track 41 in the direction corresponding to the write order for each setting operation unit. For example, if track #r, track #r+1, and track #r+2 are selected in a certain setting operation unit, track #r+1, track #r+2, and track #r+3 are selected in the next setting operation unit.

[0108] The controller 30 selects a digital area from the first target track (S202). The digital area selected in S202 is recorded as the first target digital area.

[0109] The controller 30 determines whether the write current in the first target digit area has been set ( S203 ).

[0110] In one setting operation unit, the write current in the digital area included in the second target track or the digital area included in the third target track may be set through the processing of S210, S211, S213, or S214 described later. As a result, among the digital areas included in the track 41 selected as the first target track, there may be digital areas for which the write current has already been set in the previous setting operation unit or the previous setting operation unit. In S203, the controller 30 determines whether the write current in the first target digital area has already been set in the previous setting operation unit or the previous setting operation unit.

[0111] When the write current in the first target digital area has not been set ( S203 : No), the controller 30 determines whether the value written in the first target digital area is “0” ( S204 ).

[0112] When the value written to the first target digital area is not “0” ( S204 : No), the controller 30 determines whether the value written to the first target digital area is “1” ( S205 ).

[0113] When the value written to 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 ).

[0114] When the value written to the first target digital area is not "1" (S205: No), that is, when the value written to the first target digital area is "-1", the controller 30 sets the write current in the first target digital area to WC -1 (S207).

[0115] If the value written to the first target digital area is "0" (S204: Yes), the controller 30 determines whether the value written to the digital area adjacent to the first target digital area included in the second target track is also "0" (S208). The digital area adjacent to the first target digital area included in the second target track is recorded as the second target digital area.

[0116] When the value written to the second target digital area is not “0” ( S208 : No), the controller 30 determines whether the value written to the second target digital area is “1” ( S209 ).

[0117] When the value written to the second target digital area is "1" (S209: Yes), the controller 30 sets the write current in the first target digital area to WC -1 , the write current in the second target digital area is set to WC2 (S210).

[0118] When the value written to the second target digital area is not "1" (S209: No), that is, when the value written to the second target digital area is "-1", the controller 30 sets the write current in the first target digital area to WC1 and the write current in the second target digital area to WC -2 (S211).

[0119] As described above, K is 2. Therefore, when the value written to the first target digital area and the value written to the second target digital area are both "0" (S208: Yes), the value written to the digital area adjacent to the second target digital area included in the third target track is either "1" or "-1." The digital area adjacent to the second target digital area included in the third target track is recorded as the third target digital area. Controller 30 determines whether the value written to the third target digital area is "1" (S212).

[0120] When the value written to the third target digital area is "1" (S212: YES), the controller 30 sets the write current in the first target digital area to WC1 and the write current in the second target digital area to WC -2 , the write current in the third target digital area is set to WC2 (S213).

[0121] If the value written to the third target digital area is not "1" (S212: No), that is, if the value written to the third target digital area is "-1", the controller 30 sets the write current in the first target digital area to WC -1 , set the write current in the second target digital area to WC2, and set the write current in the third target digital area to WC -2 (S214).

[0122] When the write current in the first target digital area is set (S203: Yes), or after the processing of S206, S207, S210, S211, S213, or S214, the controller 30 determines whether there is a digital area in the first target track that has not been selected as the first target digital area (S215). If there is a digital area in the first target track that has not been selected as the first target digital area (S215: Yes), the control returns to S202, and the controller 30 selects any digital area that has not been selected as the first target digital area as the new first target digital area.

[0123] When there is no digital area in the first target track that has not been selected as the first target digital area (S215: No), one setting operation unit is completed.

[0124] The state where "0" is written in the first digital area is changed by performing WC2 or WC on the second digital area. -2 When the last track includes a digital area with a value of "0" to be written, the controller 30 sets an additional track (extra track) adjacent to the last track on the side opposite to the beginning track, and performs WC2 or WC on the additional track. -2 Furthermore, in the radial direction, a portion 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 in the adjacent band area 130.

[0125] Figure 12This figure is used to illustrate an example of writing to an additional track in the first embodiment. In this figure, track #m is the last track in a certain band area 130, and track #m-1 is the track 41 immediately preceding track #m in the writing order.

[0126] In track #m, "0" is written to digital areas D10, D12, and D14. Thus, in order to invert the polarity of each of the digital areas D10, D12, and D14, which are part of the digital area, the controller 30 sets an additional track adjacent to track #m and performs WC2 or WC on the digital areas D11, D13, and D15 in the additional track. -2 The write current is written.

[0127] exist Figure 12 In the example shown, a pre-setup is performed to write to the additional track using a write current of WC2. Consequently, the controller 30 sets the write currents of digital areas D10, D12, and D14 to negative currents according to this pre-setup. The controller 30 then writes to digital areas D11, D13, and D15 using a write current of WC2.

[0128] Note that the method of setting the write current when writing the additional track is not limited to the above-described method.

[0129] When writing "1" or "-1" to the digital area of ​​track #m, controller 30 magnetizes the write-destination digital area to a positive or negative polarity corresponding to the value to be written. After magnetizing the write-destination digital area to a positive or negative polarity, controller 30 suppresses magnetization of the digital area adjacent to the write-destination digital area in the additional track.

[0130] In the description of the first embodiment, WC1 or WC2 is used as the magnetization method for magnetizing the first digit region while suppressing the influence on the magnetization of the third digit region. -1 The operation of magnetizing the first digit area by the write current of WC1 or WC is an example of the first magnetization operation. -1 The recording width in the radial direction achieved by the magnetic head 22 when the write current is φ is an example of the first recording width.

[0131] As an operation to magnetize the first digit region while reversing the magnetization of a portion of the third digit region, WC2 or WC -2 The operation of magnetizing by the write current of WC2 or WC is an example of the second magnetizing operation. The recording width achieved by the second magnetizing operation, that is, the recording width achieved by the second magnetizing operation, -2The recording width in the radial direction achieved by the magnetic head 22 when the write current is φ is an example of the second recording width.

[0132] "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. Writing "1" to the first digital area is an example of a first write operation. Writing "-1" to the first digital area is an example of a second write operation. Writing "0" to the first digital area is an example of a third write operation.

[0133] As described above, the magnetic disk drive 1 of the first embodiment has the following features. Specifically, the magnetic head 22 can perform a magnetizing operation on the magnetic disk 11 to either positive or negative polarity. The magnetizing operation includes a first magnetizing operation in which the magnetic disk 11 is magnetized with a first recording width, and a second magnetizing operation in which the magnetic disk 11 is magnetized with a second recording width that is 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 digital region (i.e., the first write operation), an operation to write "-1" to the first digital region (i.e., the second write operation), or an operation to write "0" to the first digital region (i.e., the third write operation). In the first write operation, the controller 30 magnetizes the first digital region to positive polarity using either the first magnetizing operation or the second magnetizing operation. In the second write operation, the controller 30 magnetizes the first digital region to negative polarity using either the first magnetizing operation or the second magnetizing operation. In the third write operation, the controller 30 magnetizes the first digit region to positive or negative polarity using the first magnetization operation or the second magnetization operation, and then magnetizes the second digit region to the opposite polarity to the first digit region using the second magnetization operation.

[0134] Thus, each digital region can be written with a value that can take three levels. That is, data is written as information represented in ternary notation on the magnetic disk 11. This increases the storage capacity compared to the magnetic disk device of the comparative example without increasing the number of digital regions.

[0135] Furthermore, according to the first embodiment, in the third write operation, the controller 30 magnetizes the second digit region by the second magnetization operation, thereby inverting the magnetization of a portion of the first digit region.

[0136] As a result, the first digit region can be in three states: entirely magnetized to positive polarity, entirely magnetized to negative polarity, and partially magnetized to positive polarity and the remainder to negative polarity. This allows writing values ​​that can take on three levels into each digit region.

[0137] Furthermore, according to the first embodiment, the controller 30 determines the direction of the write current used in the second digital region, i.e., the polarity of the second digital region, by determining the value to be written to the second digital region during the third write operation. The controller 30 then magnetizes the second digital region to a polarity opposite to that of the second digital region.

[0138] Furthermore, according to the first embodiment, when the value written to the third digital region is "1" or "-1," the controller 30 magnetizes the first digital region using the first magnetization operation. When the value written to the third digital region is "0," the controller 30 magnetizes the first digital region using the second magnetization operation.

[0139] Thus, the third digit region can assume three states: entirely magnetized to positive polarity, entirely magnetized to negative polarity, or partially magnetized to one of positive and negative polarity and the remaining portion magnetized to the other of positive and negative polarity. Thus, each digit region can be written with values ​​that can take on three levels.

[0140] Furthermore, according to the first embodiment, in the first write operation, after the first digit region is magnetized to positive polarity by the first magnetization operation or the second magnetization operation, the second digit region is magnetized to positive polarity or negative polarity by the first magnetization operation. In the second write operation, after the first digit region is magnetized to negative polarity by the first magnetization operation or the second magnetization operation, the second digit region is magnetized to positive polarity or negative polarity by the first magnetization operation.

[0141] As a result, the first digit region is entirely magnetized to a positive polarity or entirely magnetized to a negative polarity.

[0142] Furthermore, according to the first embodiment, writing is performed in units of tracks 41 in one direction from the beginning track to the end track of the plurality of tracks 41 included in one band area 130. Figure 12 As described above, the controller 30 can write a "0" (referred to as the fourth write operation) to a digital region (referred to as the fourth digital region) included in the last track. In the fourth write operation, the controller 30 magnetizes the fourth digital region to either positive or negative polarity using the first magnetization operation or the second magnetization operation. Subsequently, the controller 30 magnetizes the fifth digital region included in the additional track to an opposite polarity using the second magnetization operation for the fourth digital region. The fifth digital region is adjacent to the fourth digital region.

[0143] Furthermore, according to the first embodiment, Figure 12As shown, the controller 30 can execute an operation of writing "1" or "-1" to the fourth digit area (referred to as the fifth write operation). In the fifth write operation, the controller 30 magnetizes the fourth digit area to positive polarity or negative polarity using the first magnetization operation or the second magnetization operation, and then suppresses magnetization of the fifth digit area included in the additional track.

[0144] Furthermore, according to the first embodiment, in the first magnetizing operation, the controller 30 supplies WC1 or WC -1 In the second magnetizing operation, the controller 30 supplies the magnetic head 22 with a current greater than that in the first magnetizing operation, WC2 or WC -2 The write current

[0145] Thus, in the second magnetizing operation, magnetization can be performed with a larger recording width than in the first magnetizing operation.

[0146] (Second embodiment)

[0147] In the second embodiment, an example of the operation of the controller 30 generating write data represented in ternary format is described. Here, it is assumed that K=2. Figure 10 Executed in S101.

[0148] The controller 30 receives binary data from the host 2. The controller 30 converts the received data to generate write data in ternary format. The operation of converting the binary data into ternary data is performed, for example, in the RWC 25. Alternatively, the conversion operation may be performed in a circuit other than the RWC 25.

[0149] Figure 13 This is a diagram for explaining an example of a method for generating write data executed by the controller 30 according to the second embodiment.

[0150] The controller 30 converts the three-digit information represented in binary into two-digit information represented in ternary. The three-digit information represented in binary can take eight values. The two-digit information represented in ternary can take nine values. The controller 30 establishes a one-to-one correspondence between the eight possible values ​​of the three-digit information represented in binary and the eight values ​​of the two-digit information represented in ternary, excluding "00." Based on this correspondence, the controller 30 generates the two-digit information represented in ternary.

[0151] The controller 30 uses the value of the first bit of the two-bit information generated in ternary representation as the write data of a certain track 41 (for example, track #p), and uses the value of the second bit of the two-bit information as the write data of the track 41 adjacent to track #p (that is, track #p+1).

[0152] Since 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 digital regions where "0" is written and arranged continuously in the radial direction is 2 or less.

[0153] (Third embodiment)

[0154] When the polarity of a portion of the third digital region is inverted during a write operation to the first digital region, the ratio of the inverted portion relative to the third digital region can be controlled. This allows the third level of the signal obtained from the third digital region during a read operation to be further controlled to multiple levels. In other words, values ​​that can take on four or more levels can be written to each digital region.

[0155] In the third embodiment, a technique for writing a value that can take four levels in each digital area is described. Furthermore, in the third embodiment, matters that differ from the first embodiment are described. Matters that are the same as in the first embodiment are omitted or briefly described.

[0156] Figure 14 This is a diagram for explaining a method of writing a value that can take four levels according to the third embodiment.

[0157] exist Figure 14 In the example shown, the values ​​written to a digital region can be "-1," "-0.3," "0.3," and "1." "1" is associated with a state in which the entire digital region is positive. "0.3" is associated with a state in which approximately two-thirds of the digital region is positive. "-0.3" is associated with a state in which approximately one-third of the digital region is positive. "-1" is associated with a state in which the entire digital region is negative.

[0158] The controller 30 can control the current amount of the write current supplied to the magnetic head 22 to WCa3, WCa2, ​​WCa1, and WCa2. -1 、WCa -2 and WCa -3 WCa1, WCa2, ​​and WCa3 are positive write currents. The current of WCa3 is larger than that of WCa2, ​​and the current of WCa2 is larger than that of WCa1. -1 、WCa -2 and WCa -3 Is the negative write current. WCa -3 The current of WCa3 is roughly equal to that of WCa -2 The current of WCa2 is roughly equal to that of WCa -1 The current of WCa1 is roughly equal to that of WCa1.

[0159] The radial recording width achieved by the magnetic head 22 when the write current WCa1 is supplied is different from that achieved by the magnetic head 22 when the write current WCa1 is supplied. -1 The recording width in the radial direction of the magnetic head 22 when the write current WCa2 is supplied is substantially equal to the recording width in the radial direction of the magnetic head 22 when the write current WCa2 is supplied. -2 The recording width in the radial direction of the magnetic head 22 when the write current of WCa3 is supplied is substantially equal to the recording width in the radial direction of the magnetic head 22 when the write current of WCa3 is supplied. -3 The radial recording widths achieved by the magnetic head 22 when the write current is approximately the same.

[0160] In addition, as long as the same record width can be obtained, WCa -3 The current of WCa3 may not be equal to the current of WCa. -2 The current of WCa2 may not be equal to that of WCa2. -1 The current of may not be equal to the current of WCa1.

[0161] In addition, by being supplied with WCa2 or WCa -2 The radial recording width of the magnetic head 22 when the write current is supplied is greater than that of the magnetic head 22 when the write current is supplied WCa1 or WCa -1 The radial recording width of the magnetic head 22 is large when the write current is high. -3 The radial recording width of the magnetic head 22 when the write current is supplied is greater than that of the magnetic head 22 when the write current is supplied. -2 The radial recording width achieved by the magnetic head 22 when the write current is large.

[0162] Specifically, by being supplied with WCa1 or WCa -1 The recording width in the radial direction of the magnetic head 22 when the write current is 0 is a recording width that can suppress the influence on the magnetism of the third digit area as much as possible. -2 The radial recording width of the magnetic head 22 when the write current is 0.001 is a recording width that can magnetize approximately 1 / 3 of the third digit area. -3 The radial recording width achieved by the magnetic head 22 when the write current is φ is a recording width capable of magnetizing approximately two-thirds of the third digit area.

[0163] Similar to the first embodiment, the direction and amount of the write current in the first digital area are set based on the value written to the first digital area, the direction of the write current in the second digital area (in other words, the value written to the second digital area), and the value written to the third digital area.

[0164] For example, the value written to digital region D20 is set to "-0.3." If digital region D20 is considered the first digital region, digital region D21 corresponds to the second digital region. Since the value written to digital region D21 is "-1," a negative write current is used in digital region D21. Consequently, a positive write current is used in digital region D20.

[0165] When the digital area D21 is regarded as the first digital area, the digital area D20 corresponds to the third digital area. Under the condition that a positive write current is used in the digital area D20 and a negative write current is used in the digital area D21, in order to make the digital area D20 such that approximately 1 / 3 of the area of ​​the digital area D20 is in a positive polarity state, that is, a state corresponding to "-0.3", the controller 30 uses WCa in the digital area D21. -3 The write current

[0166] Furthermore, for example, the value written to digital region D22 is "-0.3". The value written to digital region D23 is "1", so a positive write current is used in digital region D23. Consequently, a negative write current is used in digital region D22.

[0167] Under the condition that a negative write current is used in the digital area D22 and a positive write current is used in the digital area D23, in order to make the digital area D22 a state in which approximately 1 / 3 of the digital area D22 is positive polarity, that is, a state corresponding to "-0.3", the controller 30 uses a write current of WCa2 in the digital area D23.

[0168] Furthermore, in the third embodiment, writing "1" to the first digit area is an example of the first write operation. Writing "-1" to the first digit area is an example of the second write operation. Writing "0.3" to the first digit area and writing "-0.3" to the first digit area are both examples of the third write operation.

[0169] That is, in the third embodiment, the controller 30 can write a value that can take two levels in each digital region by varying the ratio of the portion in which the magnetization inversion is performed in the digital region during the third write operation, depending on whether the value to be written is "0.3" or "-0.3." In other words, through the first, second, and third write operations, a total of four levels of values ​​can be written in each digital region.

[0170] Furthermore, by varying the ratio of the portion in which the magnetization inversion is performed in the digital region by three or more different ratios in the third write operation, the controller 30 can write values ​​that can take on three or more levels in each digital region through the third write operation. That is, through the first, second, and third write operations, a total of five or more levels of values ​​can be written in each digital region.

[0171] (Fourth embodiment)

[0172] 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 recording width control method is not limited to the method using only the control of the magnitude of the write current supplied to the magnetic head 22.

[0173] An energy-assisted recording method is known as a method for magnetizing a magnetic disk. The energy-assisted recording method applies a certain amount of energy to the magnetic disk, thereby magnetizing the magnetic disk even with a small write current.

[0174] Energy-assisted recording methods include a microwave-assisted magnetic recording (MAMR) method and a heat-assisted magnetic recording (HAMR) method.

[0175] Microwave-assisted magnetic recording reduces the magnetic field required for magnetization by applying microwaves to the disk. Thermally assisted magnetic recording reduces the coercive force of the disk by locally heating the disk using near-field light or the like.

[0176] When energy-assisted recording is used, the controller 30 can control the recording width by controlling the amount of assist provided by microwaves, heat, etc. (hereinafter referred to as energy assist). The controller 30 can increase the recording width as the energy assist amount increases.

[0177] In the fourth embodiment, the magnetic head 22 includes an auxiliary element capable of applying energy to the magnetic disk 11. The auxiliary element is an element that generates microwaves or near-field light. The controller 30 controls the energy assist amount, that is, the intensity of the microwaves or near-field light generated by the auxiliary element.

[0178] Figure 15 This is a diagram for explaining an example of a recording width control method according to the fourth embodiment.

[0179] exist Figure 15In FIG. 1 , part (A) shows the written 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 written data of track #n and track #n+1 shown in part (A) are the same as those of track #n+1. Figures 6-8 Part (A) shows that the written data of track #n and track #n+1 are the same.

[0180] like Figure 15 As shown, the controller 30 can control the magnitude of the write current supplied to the magnetic head 22 to be WCb1 and WCb -1 WCb1 is the positive write current. -1 Is the negative write current. WCb -1 The amount of current flowing through WCb1 is equal to that flowing through WCb2.

[0181] Furthermore, the controller 30 can control the energy assist amount to EA1 and EA2.

[0182] WCb1 or WCb is supplied to the magnetic head 22. -1 The radial recording width achieved by the magnetic head 22 when the energy assist of EA1 is performed when the write current is 0.5 is a recording width that can suppress the influence on the magnetism of the third digit area as much as possible. In addition, WCb1 or WCb is supplied to the magnetic head 22. -1 The radial recording width of the magnetic head 22 in the case of the energy assist of EA2 when the write current is 1000W is set to be enough to magnetize approximately half of the third digit area. -1 The radial recording width of the magnetic head 22 when the energy assist of EA2 is performed at a write current of 1 is greater than that of the magnetic head 22 when WCb1 or WCb is supplied to the magnetic head 22. -1 When the write current is 0.001, the radial recording width achieved by the magnetic head 22 is large when the energy assist of EA1 is performed.

[0183] The controller 30 sets the direction of the write current in the same manner as in the first embodiment. However, the controller 30 controls the energy assist amount to multiple levels instead of controlling the current amount of the write current to multiple levels. Specifically, the controller 30 sets the energy assist amount to EA1 instead of setting the write current to WC1 or WC -1 The controller 30 sets the energy assist amount to EA2 instead of setting the write current to WC2 or WC -2 . Thus, it is possible to achieve Figure 7 The magnetization state of part (C) shows the same magnetization state.

[0184] That is, in the fourth embodiment, the operation of magnetizing while applying the energy EA1 via the auxiliary element corresponds to the first magnetizing operation of magnetizing with the first recording width. The operation of magnetizing while applying the energy EA2 greater than EA1 via the auxiliary element corresponds to the second magnetizing operation of magnetizing with the second recording width.

[0185] Thus, according to the fourth embodiment, the controller 30 applies the energy of EA1 via the auxiliary element in the first magnetizing operation. The controller 30 applies the energy of EA2 which is greater than EA1 via the auxiliary element in the second magnetizing operation.

[0186] Thus, by controlling the amount of energy applied from the auxiliary element to the magnetic disk 11 in multiple levels, three levels of values ​​can be written to each digital area. This increases the storage capacity compared to the magnetic disk device according to the comparative example without increasing the number of digital areas.

[0187] In the fourth embodiment, the energy assist amount is controlled to two levels, EA1 and EA2. The energy assist amount may also be controlled to three or more levels. By controlling the energy assist amount to three or more levels, for example, as in the third embodiment, values ​​that can take on four or more levels can be written into each digital area.

[0188] According to the first, second, third, and fourth embodiments, the controller 30 performs the above-described operations, etc., so that the multiple digital regions included in the magnetic disk 11 include the digital regions described below. That is, the multiple digital regions include a digital region that is magnetized to positive polarity as a whole by the magnetic head 22. The multiple digital regions include a digital region that is magnetized to negative polarity as a whole by the magnetic head 22. The multiple digital regions include a digital region that is magnetized to one of positive and negative polarity in a radial direction by the magnetic head 22, and the remaining portion is magnetized to the other of positive and negative polarity.

[0189] Furthermore, according to the first, second, third, and fourth embodiments, the boundary between the circumferential digital regions is aligned between a first track, which is a certain track, and a second track, which is adjacent to the first track. This allows the digital regions to be magnetized with either positive or negative polarity in a radial direction, while the remaining portion is magnetized with the other polarity.

[0190] Furthermore, according to the first, second, third, and fourth embodiments, the number of digit regions with inverted polarity arranged in the radial direction is limited to a predetermined number (K ​​in the above example) or less. For example, K is 2.

[0191] According to the first embodiment, when the polarity of a portion of each of the plurality of digit regions is inverted, the ratio R of the inverted portion to the digit region is uniform across the plurality of digit regions. Specifically, the ratio R is approximately 0.5.

[0192] Furthermore, according to the third embodiment, when the polarity of a portion of each of the plurality of digital regions is inverted, the ratio R of the inverted portion to the digital region 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).

[0193] While several embodiments of the present invention have been described above, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways and can be omitted, replaced, or modified without departing from the gist of the invention. These embodiments and / or their variations are intended to be within the scope and spirit of the invention and are encompassed by the invention as set forth in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: 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 performs a magnetizing operation on the magnetic disk to magnetize the magnetic disk to either a first polarity or a second polarity that is opposite to the first polarity, the magnetizing operation including a first magnetizing operation of magnetizing the magnetic disk with a first recording width and a second magnetizing operation of magnetizing the magnetic disk with a second recording width that is larger than the first recording width; and The controller is capable of executing any of a first write action, a second write action, and a third write action, wherein the first write action is a write action of writing a first value to a first regional unit, the second write action is a write action of writing a second value different from the first value to the first regional unit, and the third write action is a write action of writing a third value different from both the first value and the second value to the first regional unit, wherein the first regional unit is a regional unit included in a first track that is one of the plurality of tracks. the controller, In the first writing operation, the first unit region is magnetized to the first polarity by the first magnetizing operation or the second magnetizing operation. In the second writing operation, the first regional unit is magnetized to the second polarity by the first magnetizing operation or the second magnetizing operation. In the third writing action, the first regional unit is magnetized to either the first polarity or the second polarity by the first magnetization action or the second magnetization action, and then the second regional unit is magnetized to the polarity opposite to that of the first regional unit by the second magnetization action. The second regional unit is a regional unit adjacent to the first regional unit in the radial direction, included in the second track of the multiple tracks, which is a track adjacent to the first track and written after the first track.

2. The magnetic disk device according to claim 1, The controller, in the third write operation, By magnetizing the second regional unit by the second magnetizing operation, the magnetization of a portion of the first regional unit is reversed.

3. The magnetic disk device according to claim 1, The controller determines the polarity of the second regional unit in the third write operation, and magnetizes the first regional unit to a polarity opposite to the determined polarity of the second regional unit.

4. The magnetic disk device according to claim 1, In the first write operation, the second write operation, and the third write operation, the controller When the value written to the third area unit is the first value or the second value, the first area unit is magnetized by the first magnetizing operation, the third area unit being an area unit radially adjacent to the first area unit and included in a third track that is adjacent to the first track and written before the first track among the plurality of tracks, When the value written to the third area unit is the third value, the first area unit is magnetized by the second magnetizing operation.

5. The magnetic disk device according to claim 1, the controller, In the first writing operation, after the first regional unit is magnetized to the first polarity by the first magnetizing operation or the second magnetizing operation, the second regional unit is magnetized to either the first polarity or the second polarity by the first magnetizing operation. In the second writing operation, after the first regional unit is magnetized to the second polarity by the first magnetizing operation or the second magnetizing operation, the second regional unit is magnetized to either the first polarity or the second polarity by the first magnetizing operation.

6. The magnetic disk device according to claim 1, the controller, A plurality of fourth tracks continuous in the radial direction among the plurality of tracks are written in an SMR method, i.e., a shingled magnetic recording method, and the writing order of the plurality of fourth tracks in units of tracks is from the fifth track of the fourth track, which is one end in the radial direction of the plurality of fourth tracks, to the sixth track of the fourth track, which is the other end in the radial direction of the plurality of fourth tracks. A fourth write operation can be executed, wherein the fourth write operation is a write operation of writing the third value to a fourth area unit which is an area unit included in the sixth track. In the fourth write action, the fourth regional unit is magnetized to either the first polarity or the second polarity by the first magnetization action or the second magnetization action, and then the fifth regional unit is magnetized to the polarity opposite to that of the fourth regional unit by the second magnetization action. The fifth regional unit is a regional unit adjacent to the fourth regional unit in the radial direction and is included in the track on the side opposite to the fifth track in the two tracks adjacent to the sixth track.

7. The magnetic disk device according to claim 6, the controller, A fifth write operation can be executed, wherein the fifth write operation is a write operation for writing the first value or the second value to the fourth area unit. In the fifth writing operation, the fourth regional unit is magnetized to the first polarity or the second polarity by the first magnetizing operation or the second magnetizing operation, and then the magnetization of the fifth regional unit is suppressed.

8. The magnetic disk device according to any one of claims 1 to 7, the controller, supplying a first amount of write current to the magnetic head in the first magnetizing operation, In the second magnetizing operation, a second amount of write current greater than the first amount is supplied to the magnetic head.

9. The magnetic disk device according to any one of claims 1 to 7, The magnetic head has an auxiliary element for applying energy to the magnetic disk. the controller, In the first magnetizing operation, a third amount of energy is applied to the magnetic disk via the auxiliary element. In the second magnetizing operation, a fourth amount of energy greater than the third amount is applied to the magnetic disk by the auxiliary element.

10. The magnetic disk device according to claim 1, The third value includes a plurality of fourth values, and the plurality of fourth values ​​are different from each other. The controller varies the ratio of the portion of the first regional unit where magnetization is reversed with respect to the first regional unit for each of the plurality of fourth values ​​in the third write operation.

11. A magnetic disk device comprising: a magnetic disk provided with a plurality of tracks, each of the plurality of tracks including a plurality of area units arranged along the track; and A magnetic head, which magnetizes the disk, The plurality of area units include: The first area unit is magnetized to a first polarity as a whole by the magnetic head; The second regional unit is magnetized as a whole to a second polarity that is opposite to the first polarity; and In the third area unit, a portion in the radial direction is magnetized by one of the first polarity and the second polarity by the magnetic head, and the remaining portion is inverted by the other of the first polarity and the second polarity.

12. The magnetic disk device according to claim 11, The boundaries between the plurality of area units of a first track, which is one of the plurality of tracks, are aligned with the boundaries between the plurality of area units of a second track, which is one of the plurality of tracks adjacent to the first track.

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

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

15. The magnetic disk device according to claim 14, The ratio is 0.

5.

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

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

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