Disk device

Abstract

The embodiment provides a magnetic disk device capable of increasing the recording capacity by taking into account the positioning accuracy of the magnetic head. The magnetic disk device of the embodiment comprises: a plurality of magnetic disks having recording layers, arranged at intervals on the same axis; and a plurality of magnetic heads having magnetic poles for generating recording magnetic fields in a perpendicular direction to the recording layers, arranged at intervals along the parallel direction of the magnetic disks, wherein among a plurality of groups obtained by classifying the magnetic disks according to index values ​​representing the overwriting characteristics of the magnetic disks, the group to which the magnetic disks having higher index values ​​belong is arranged at an outer position farther from the center in the parallel direction.

Description

[0001] This application is a divisional application of the application with application number 202011610120.5, application date December 30, 2020, and invention name “Disk Device”.

[0002] This application claims the priority of Japanese Patent Application No. 2020-85002 (filing date: May 14, 2020) as a basic application, and the entire contents of the basic application are incorporated herein by reference. Technical Field

[0003] An embodiment of the present invention relates to a magnetic disk device. Background Art

[0004] As a means for increasing the recording capacity of a magnetic disk device, it is effective to increase the number of magnetic disks mounted in the device. However, in the case of limited mounting space, in order to increase the number of disks, it is necessary to reduce the thickness of the magnetic disks and the spacing between adjacent magnetic disks. Even when the thickness and spacing of the magnetic disks are reduced, it is also required that the frequency of errors caused by the deterioration of the positioning accuracy of the magnetic head when writing or reading data does not increase. The positioning accuracy of the magnetic head is affected by the torsion (twist) of the rotating shaft of the actuator when the magnetic head is driven, and therefore, the more the magnetic head is arranged on the cover side and the base side of the frame of the magnetic disk device, the easier it is to deteriorate. That is, the positioning accuracy of the magnetic head is different according to the position in the direction (parallel (side by side) direction) in which the magnetic head is arranged. Summary of the invention

[0005] The embodiment of the present invention provides a magnetic disk device capable of increasing the recording capacity in consideration of the position of the magnetic head in the parallel direction.

[0006] A magnetic disk device according to an embodiment includes:

[0007] A plurality of magnetic disks having recording layers, arranged on the same axis with intervals therebetween; and

[0008] A plurality of magnetic heads having magnetic poles for generating a recording magnetic field in a perpendicular direction to the recording layer are arranged at intervals along the parallel direction of the magnetic disks.

[0009] Among a plurality of groups obtained by classifying the magnetic disks according to index values ​​indicating overwriting characteristics of the magnetic disks, the group to which the magnetic disks having higher index values ​​belong is arranged at an outer position farther from the center in the parallel direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a block diagram schematically showing a hard disk drive (HDD) according to the embodiment.

[0011] Figure 2 It is a side view schematically showing a magnetic head, a suspension, and a magnetic disk in the HDD.

[0012] Figure 3 It is a cross-sectional view showing an enlarged view of the head portion of the magnetic head.

[0013] Figure 4 It is a perspective view schematically showing a write head of the magnetic head.

[0014] Figure 5 It is a cross-sectional view showing an enlarged front end portion of the writing head.

[0015] Figure 6 This is a plan view of the write head of the magnetic head as viewed from the ABS side.

[0016] Figure 7 This is a diagram schematically showing an example of the arrangement of the magnetic disk and the magnetic head.

[0017] Figure 8 FIG. 1 is a diagram showing an example of a value of a magnetic pole width of each write head among the plurality of magnetic heads.

[0018] Fig. 9 This is a diagram showing the relationship between the cross track position used when measuring the width of the magnetic characteristic of the main magnetic pole and the signal output.

[0019] Fig.10 It is a diagram schematically showing the relationship between the number of recording times (Write count) and the error rate (Error Rate) for the recording track of the magnetic disk.

[0020] Fig.11 This is a diagram showing an example of classification of the magnetic disks based on the overwrite characteristic (OW).

[0021] Fig.12 1 is a flowchart showing an example of control of recording current in the HDD (recording current control processing). DETAILED DESCRIPTION

[0022] Hereinafter, a magnetic disk device according to an embodiment will be described with reference to the drawings.

[0023] In addition, the disclosure is only an example, and appropriate changes that maintain the purpose of the invention and can be easily thought of by those skilled in the art are of course included in the scope of the present invention. In addition, in order to make the description clearer, the drawings sometimes schematically show the width, thickness, shape, etc. of each part compared to the actual form, but it is only an example and does not limit the interpretation of the present invention. In addition, in this specification and each figure, the same reference numerals are marked for the same elements as those described in the previous figures, and the detailed description is sometimes appropriately omitted or simplified.

[0024] (First embodiment)

[0025] A hard disk drive (hereinafter referred to as HDD) according to the first embodiment will be described in detail as a magnetic disk device. Figure 1 is a block diagram schematically showing an HDD according to the first embodiment. Figure 2 It is a side view showing the magnetic head and magnetic disk in a suspended state.

[0026] like Figure 1 As shown, HDD 10 has a rectangular frame 11, a magnetic disk 12 as a recording medium arranged in the frame 11, a spindle motor 21 for supporting and rotating the magnetic disk 12, and a plurality of magnetic heads 16 for writing and reading data from the magnetic disk 12. The frame 11 has a rectangular box-shaped base (not shown) with an upper opening and a cover (not shown) covering the opening of the base. The base is composed of, for example, a rectangular bottom wall and side walls rising along the periphery of the bottom wall, and is integrally formed of aluminum or the like. The cover is, for example, screwed to the side wall of the base by a plurality of screws to seal the opening of the base in an airtight manner, and is formed of stainless steel or the like.

[0027] The HDD 10 includes a head actuator 18 that moves and positions the magnetic head 16 on an arbitrary recording track on the magnetic disk 12. The head actuator 18 includes a carriage assembly 20 that movably supports the magnetic head 16 and a voice coil motor (hereinafter referred to as VCM) 22 that rotates the carriage assembly 20.

[0028] The HDD 10 includes a head amplifier IC 30 for driving the magnetic head 16, a main controller 90, and a driver IC 92. The head amplifier IC 30 is provided, for example, in the carriage assembly 20 and is electrically connected to the magnetic head 16. The head amplifier IC 30 includes a recording current supply circuit (recording current supply unit) 91 for supplying a recording current to a recording coil of the magnetic head 16, a bias voltage supply circuit 93 for supplying a bias voltage (driving current) to a spin torque oscillator (hereinafter referred to as STO) described later, a heater voltage supply circuit 98 for supplying a driving voltage to a heater described later, and an amplifier (not shown) for amplifying a signal read by the magnetic head 16.

[0029] The main controller 90 and the driver IC 92 are composed of, for example, a control circuit substrate (not shown) provided on the back side (base) of the frame 11. The main controller 90 includes an R / W channel 94, a hard disk controller (hereinafter referred to as HDC) 96, a microprocessor (hereinafter referred to as MPU) 97, and a memory 80. The main controller 90 is electrically connected to the magnetic head 16 via the head amplifier IC 30. The main controller 90 is electrically connected to the VCM 22 and the spindle motor 21 via the driver IC 92. The HDC 96 can be connected to the host 95.

[0030] like Figure 1 and Figure 2 As shown, the magnetic disk 12 is constructed as a perpendicular magnetic recording medium. The magnetic disk 12 has, for example, a substrate 101 formed of a non-magnetic body and formed in the shape of a disk with a diameter of 88.9 mm (3.5 inches). On each surface (upper and lower surfaces) of the substrate 101, a soft magnetic layer 102 as a base layer formed of a material exhibiting soft magnetic properties, a magnetic recording layer (recording layer) 103 having magnetic anisotropy in a perpendicular direction relative to the surface of the magnetic disk 12, and a protective film 104 are stacked in this order from the lower layer to the upper layer. The magnetic disk 12 is engaged with the hub of the spindle motor 21 in a coaxial manner. The magnetic disk 12 is rotated in the direction of arrow B at a predetermined speed by the spindle motor 21.

[0031] The carriage assembly 20 includes a bearing portion 24 rotatably supported by the frame 11 and a plurality of suspensions 26 extending from the bearing portion 24. Figure 2 As shown, the magnetic head 16 is supported by the extended ends of the suspensions 26. The magnetic head 16 is electrically connected to the head amplifier IC 30 via a wiring member (flexure) 28 provided in the carriage assembly 20.

[0032] like Figure 2 As shown, the magnetic head 16 is constructed as a suspension type head, and has a slider 42 formed in a substantially rectangular parallelepiped shape, and a head 44 formed at the end of the outflow end (tail) side of the slider 42. The slider 42 is formed of, for example, a sintered body of aluminum oxide and titanium carbide (AlTiC), and the head 44 is formed of a multi-layered film. The slider 42 is mounted on the gimbal portion 41 of the wiring member 28.

[0033] The slider 42 has a disk-facing surface (air bearing surface (hereinafter referred to as ABS)) 43 of a rectangular shape facing the surface of the magnetic disk 12. The slider 42 is maintained in a state of being suspended by a predetermined amount from the surface of the magnetic disk 12 by using the air flow C generated between the disk surface and the ABS 43 by the rotation of the magnetic disk 12. The direction of the air flow C coincides with the rotation direction B of the magnetic disk 12. The slider 42 has a leading end 42a located on the inflow side of the air flow C and a trailing end 42b located on the outflow side of the air flow C. As the magnetic disk 12 rotates, the magnetic head 16 moves relative to the magnetic disk 12 in the direction of arrow A (head movement direction), that is, in the direction opposite to the rotation direction B of the disk.

[0034] Figure 3 1 is a cross-sectional view showing the head 44 of the magnetic head 16 and the magnetic disk 12 in an enlarged manner. The head 44 has a read head (reproduction head) 54 and a write head (recording head) 58 formed on the tail end 42b of the slider 42 by a thin film process, and is formed as a separate type magnetic head. The read head 54 and the write head 58 are covered by a non-magnetic protective insulating film 53 except for the portion exposed at the ABS 43 of the slider 42. The protective insulating film 53 constitutes the outer shape of the head 44.

[0035] The long direction of the recording track of the magnetic recording layer 103 formed on the magnetic disk 12 is defined as a downtrack direction DT, and the width direction of the recording track is defined as a crosstrack direction WT.

[0036] The read head 54 includes a magnetoresistance effect element 55, and a first magnetic shielding film 56 and a second magnetic shielding film 57 arranged on the leading side (inflow side) and the trailing side (outflow side) of the magnetoresistance effect element 55 in the following track direction DT so as to sandwich the magnetoresistance effect element 55. The magnetoresistance effect element 55, the first magnetic shielding film 56, and the second magnetic shielding film 57 extend substantially perpendicularly to the ABS 43. The lower ends of the magnetoresistance effect element 55, the first magnetic shielding film 56, and the second magnetic shielding film 57 are exposed at the ABS 43.

[0037] The write head 58 is disposed on the trailing end 44 b side of the slider 42 relative to the read head 54 . Figure 4 This is a three-dimensional view of the write head 58 obtained by cutting the write head 58 in the middle of the track. Figure 5 FIG. 2 is a cross-sectional view showing an enlarged front end portion (ABS side end portion) of the write head 58. Figure 6 This is a plan view of the write head 58 as viewed from the ABS side.

[0038] like Figure 3 and Figure 4As shown, the write head 58 includes a main magnetic pole (magnetic pole) 60 that generates a recording magnetic field in a perpendicular direction to the surface of the magnetic disk 12, a trailing shield (write shield) 62 disposed on the trailing side of the main magnetic pole 60 and opposed to the main magnetic pole 60 with a write gap WG, a leading shield 64 opposed to the leading side of the main magnetic pole 60, a pair of side shields 63 disposed on both sides of the main magnetic pole 60 in the cross-track direction CT, and a high-frequency oscillation element such as a spin torque oscillator (STO) 65 disposed between the main magnetic pole 60 and the trailing shield 62 in the write gap WG. The main magnetic pole 60 and the trailing shield 62 constitute a first magnetic core that forms a magnetic circuit, and the main magnetic pole 60 and the leading shield 64 constitute a second magnetic core that forms a magnetic circuit. The write head 58 includes a first recording coil 70 wound around the first magnetic core and a second recording coil 72 wound around the second magnetic core.

[0039] The main magnetic pole 60 is formed of a soft magnetic material having high magnetic permeability and high saturation magnetic flux density, and extends substantially perpendicularly to the ABS 43. The front end portion 60a of the main magnetic pole 60 on the ABS 43 side is narrowed toward the ABS 43 in a manner that the front end becomes thinner, and is formed into a columnar shape with a narrower width than other portions. The front end surface of the main magnetic pole 60 is exposed at the ABS 43 of the slider 42.

[0040] like Figure 5 and Figure 6 As shown, the front end portion 60a of the main magnetic pole 60 has a flat rear end face 60b which is opposite to the rear shield 62 with a gap. The front end portion 60a is formed into a trapezoidal shape in cross section, for example. The trapezoidal front end portion (front end face) 60a has a rear end face 60b extending in the cross-track direction CT, a leading end face 60c opposite to the rear end face 60b, and two side faces 60d. In the ABS 43, the width of the front end portion 60a, that is, the width WP of the rear end face 60b in the cross-track direction CT, roughly corresponds to the track width of the recording track in the magnetic disk 12. In the front end portion 60a, the rear end face 60b and the leading end face 60c may extend in a direction perpendicular to the ABS 43, or may extend obliquely relative to the direction perpendicular to the ABS 43. The two side faces 60d extend obliquely relative to the central axis C of the main magnetic pole 60, that is, relative to the track direction DT.

[0041] like Figure 3 to Figure 6As shown, the tail shield 62 is formed of a soft magnetic material and is provided to efficiently close the magnetic circuit through the soft magnetic layer 102 of the magnetic disk 12 directly below the main magnetic pole 60. The tail shield 62 is arranged on the tail side of the main magnetic pole 60. The tail shield 62 is formed in a substantially L-shape, and its front end portion 62a is formed in an elongated rectangular shape. The front end surface of the tail shield 62 is exposed at the ABS43 of the slider 42. The front end portion 62a has a leading side end surface (magnetic pole end surface) 62b that is opposite to the front end portion 60a of the main magnetic pole 60. The leading side end surface 62b is sufficiently longer than the width WP of the front end portion 60a of the main magnetic pole 60 and the track width of the magnetic disk 12, and extends along the cross-track direction CT. The leading side end surface 62b extends perpendicularly or slightly inclined relative to the ABS43. In the ABS 43 , the lower end edge of the leading-side end surface 62 b faces the trailing-side end surface 60 b of the main magnetic pole 60 in parallel with a write gap WG (gap length in the track direction DT) therebetween.

[0042] like Figure 4 and Figure 5 As shown, the tail shield 62 has a first connection portion 50 connected to the main magnetic pole 60. The first connection portion 50 is magnetically connected to the upper portion of the main magnetic pole 60, that is, the portion of the main magnetic pole 60 away from the ABS 43, via the non-conductive body 52. ​​The first recording coil 70 is wound around the first connection portion 50 in the first magnetic core, for example. When writing a signal to the magnetic disk 12, the first recording coil 70 is excited to flow a recording current through the first recording coil 70, so that a magnetic flux flows through the main magnetic pole 60. The recording current supplied to the first recording coil 70 and the second recording coil 72 is controlled by the main controller 90.

[0043] like Figure 4 and Figure 6 As shown, a pair of side shields 63 are arranged on both sides of the main magnetic pole 60 in the cross-track direction CT so as to be physically disconnected from the main magnetic pole 60 and connected to the tail shield 62. In the present embodiment, the side shields 63 are formed integrally with the front end portion 62a of the tail shield 62 by a high magnetic permeability material, and protrude from the leading side end surface 62b of the front end portion 62a toward the leading end side of the slider 42.

[0044] like Figure 3 to Figure 5As shown, the leading shield 64 formed of a soft magnetic body is arranged opposite to the main magnetic pole 60 on the leading side of the main magnetic pole 60. The leading shield 64 is formed into a roughly L-shaped shape, and the front end portion 64a on the ABS43 side is formed into an elongated rectangular shape. The front end surface (lower end surface) of the front end portion 64a is exposed at the ABS43. The tail side end surface 64b of the front end portion 64a extends along the cross-track direction CT. In the ABS43, the tail side end surface 64b is opposite to the leading side end surface 60c of the main magnetic pole 60 with a gap. In the present embodiment, the front end portion 64a of the leading shield 64 is formed integrally with the side shield 74 by a high magnetic permeability material.

[0045] In addition, the leading shield 64 has a second connecting portion 68 connected to the main magnetic pole 60 at a position away from the ABS 43. The second connecting portion 68 is formed of, for example, a soft magnetic body, and is magnetically connected to the upper portion of the main magnetic pole 60, that is, the portion of the main magnetic pole 60 away from the ABS 43, via the non-conductive body 59. Thus, the second connecting portion 68 forms a magnetic circuit together with the main magnetic pole 60 and the leading shield 64. The second recording coil 72 of the write head 58 is, for example, arranged to be wound around the second connecting portion 68, and a magnetic field is applied to the magnetic circuit.

[0046] like Figure 5 and Figure 6 As shown, the STO 65 functioning as a high-frequency oscillation element is arranged between the front end portion 60a of the main magnetic pole 60 and the front end portion 62a of the tail shield 62 in the write gap WG. The STO 65 has a spin injection layer 65a, an intermediate layer (non-magnetic conductive layer) 65b, and an oscillation layer 65c, and these layers are stacked in sequence from the main magnetic pole 60 side to the tail shield 62 side, that is, these layers are stacked in sequence along the track direction DT of the magnetic head 16. The spin injection layer 65a is bonded to the tail side end face 60b of the main magnetic pole 60 via the non-magnetic conductive layer (base layer) 67a. The oscillation layer 65c is bonded to the leading side end face 62b of the tail shield 62 via the non-magnetic conductive layer (cap layer) 67b. In addition, the stacking order of the spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c can also be opposite to the above, that is, they can also be stacked in sequence from the tail shield 62 side to the main magnetic pole 60 side.

[0047] The spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c respectively have a stacked surface or a film surface extending in a direction intersecting with the ABS43, for example, in an orthogonal direction. At least the lower end surface of the oscillation layer 65c, which is the lower end surface of the entire STO65 including the spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c in this embodiment, is exposed at the ABS43 and extends coplanarly (flush) with the ABS43. Alternatively, the lower end surface of the entire STO65 may also be in a direction away from the ABS43, for example, in a direction perpendicular to the ABS43, and retreat toward the depth side, that is, it may also be located at a position away from it. In addition, the lower end surface of the STO65 is not limited to a planar shape, and may also be formed into an arc shape convex upward.

[0048] like Figure 6 As shown, in ABS43, the width WS of STO65 in the cross-track direction CT is formed to be larger than the width WP of the tail end face 60b of the main magnetic pole 60 (WS>WP). In one example, the width WS of STO65 is set to be about 1.1 to 1.6 times the width WP of the main magnetic pole 60. In addition, STO65 is configured to cover at least one end edge (end in the cross-track direction) EE1, EE2 of the tail end face 60b, that is, to extend beyond the end edge to the outside of the main magnetic pole 60. In this embodiment, STO65 is configured to be symmetrical with respect to the central axis C, and covers the two end edges EE1, EE2 of the tail end face 60b in the cross-track direction CT. That is, the two ends of STO65 in the cross-track direction CT extend beyond the end edges EE1, EE2 of the tail end face 60b to the outside of the main magnetic pole 60.

[0049] like Figure 4 and Figure 5 As shown, the main magnetic pole 60 and the tail shield 62 are connected to the connection terminal 45 via wiring, and further connected to the head amplifier IC 30 and the main controller 90 via the flexible member 28. A current circuit is formed in which the STO drive current (bias voltage) is energized in series from the head amplifier IC 30 through the main magnetic pole 60, the STO 65, and the tail shield 62.

[0050] The first recording coil 70 and the second recording coil 72 are connected to the connection terminal 45 via wiring, respectively, and are further connected to the head amplifier IC30 via the flexible member 28. The second recording coil 72 is wound in the opposite direction to the first recording coil 70. When writing a signal to the magnetic disk 12, a recording current is passed from the recording current supply circuit 91 of the head amplifier IC30 to the first recording coil 70 and the second recording coil 72, and the main magnetic pole 60 is excited to flow a magnetic flux in the main magnetic pole 60. The recording current supplied to the first recording coil 70 and the second recording coil 72 is controlled by the main controller 90. In addition, the second recording coil 72 may be connected in series with the first recording coil 70. In addition, the current supply to the first recording coil 70 and the second recording coil 72 may be controlled separately.

[0051] like Figure 4 As shown, the magnetic head 16 may also include a first heater 76a and a second heater 76b. The first heater 76a is provided near the write head 58, for example, between the first recording coil 70 and the second recording coil 72, near the main magnetic pole 60. The second heater 76b is provided near the read head 54. The first heater 76a and the second heater 76b are respectively connected to the connection terminal 45 via wiring, and further connected to the head amplifier IC 30 via the flexible member 28.

[0052] When the HDD 10 constructed as described above is operated, the main controller 90 drives the spindle motor 21 through the driver IC 92 under the control of the MPU 97, so that the magnetic disk 12 rotates at a predetermined speed. In addition, the main controller 90 drives the VCM 22 through the driver IC 92, so that the magnetic head 16 moves and positions on the desired track of the magnetic disk 12. The ABS 43 of the magnetic head 16 is opposite to the disk surface with a gap. In this state, the magnetic disk 12 is read out by the read head 54, and the information is written by the write head 58.

[0053] When writing information, the bias voltage supply circuit 93 of the head amplifier IC30 applies a bias voltage to the main magnetic pole 60 and the tail shield 62 under the control of the MPU97, thereby conducting a driving current in series through the connection terminal 45, the wiring, the main magnetic pole 60, the STO 65, and the tail shield 62. The driving current flows in a direction perpendicular to the stacking surface of the STO 65. The STO 65 oscillates the spin torque to generate a high-frequency magnetic field, which is applied to the magnetic recording layer 103 of the magnetic disk 12.

[0054] At the same time, the recording current supply circuit 91 of the head amplifier IC30 supplies recording current to the first recording coil 70 and the second recording coil 72 according to the recording signal and recording mode generated from the R / W channel 94. The first recording coil 70 and the second recording coil 72 excite the main magnetic pole 60 to generate a recording magnetic field, and a recording magnetic field in a perpendicular direction is applied from the main magnetic pole 60 to the magnetic recording layer 103 of the magnetic disk 12 directly below. Thus, information is recorded in the magnetic recording layer 103 with a desired track width. By superimposing the high-frequency magnetic field of the STO65 on the recording magnetic field, the magnetization reversal of the magnetic recording layer 103 can be promoted, and magnetic recording with high magnetic anisotropy energy can be performed.

[0055] In addition, the spin torque generated by the oscillation of the STO 65 is in the opposite direction to the direction of the gap magnetic field generated between the main magnetic pole 60 and the tail shield. Therefore, the spin torque acts to reduce the leakage magnetic flux that flows directly from the main magnetic pole 60 to the tail shield 62. As a result, the amount of magnetic flux from the main magnetic pole 60 to the magnetic recording layer 103 of the magnetic disk 12 increases, and the desired data can be written to the magnetic recording layer 103.

[0056] In the present embodiment, the magnetic pole of the magnetic head 16, specifically the main magnetic pole 66 of the write head 58 of the head 44, has different magnetic pole widths according to the position of the magnetic head 16 (write head 58). The position of the magnetic head 16 here is the relative position in the direction in which a plurality of magnetic disks 12 are arranged on the same axis with predetermined intervals, that is, in the direction (parallel direction) in which a plurality of magnetic heads 16 are arranged with predetermined intervals corresponding to these magnetic disks 12. Hereinafter, the state in which the magnetic disks 12 and the magnetic head 16 are arranged in this way is referred to as a stacking state, and the direction in which these are arranged on the same axis is referred to as a stacking direction. That is, the magnetic disk 12 and the magnetic head 16 are arranged in a stacking state along the stacking direction. The magnetic pole width is the width of the main magnetic pole 60 in the cross-track direction WT, which is the width WP of the front end portion 60a, and the cross-track direction WT is the width direction of the recording track of the magnetic recording layer (recording layer) 103 formed on the magnetic disk 12.

[0057] The number of magnetic heads 16 corresponds to the number of magnetic disks 12. Figure 7 , as an example, the following manner is schematically shown: 9 magnetic disks 12 are coaxially arranged in a stacked state, and a total of 18 magnetic heads 16 are arranged one for each of the two sides of each magnetic disk 12 in a stacked state.

[0058] These magnetic disks 12 are located on the base side ( Figure 7 The disks 12a on the lower side of the cover are stacked one after another. Figure 7 In addition, correspondingly, the magnetic heads 16 are sequentially arranged in a stacked state from the magnetic head 16a located on the base side of the frame 11 to the magnetic head 16r located on the cover side.

[0059] Regarding the width WP of the main magnetic pole 60, the head 16 located in the outer layer farther from the center of the stacking direction has a wider width WP. That is, the head 16 with a wider width WP is arranged in the outer layer farther from the center of the stacking direction (the outer position farther from the center of the parallel direction). The center of the stacking direction is the middle position in the stacking direction (parallel direction) defined by the multiple heads 16 arranged in a stacked state. If another understanding is adopted, the center of the stacking direction is equivalent to the position of the center (node) of the torsion generated on the shaft supported by the bearing portion 24 of the slide assembly 20 in a freely rotatable manner.

[0060] exist Figure 7 In the example shown, the position between the magnetic head 16i and the magnetic head 16j among the 18 magnetic heads 16a to 16r arranged in a stacked state is equivalent to the center in the stacking direction. Therefore, these magnetic heads 16i and 16j are equivalent to the magnetic head 16 near the center in the stacking direction. Hereinafter, these magnetic heads 16i and 16j are appropriately referred to as central heads to distinguish them from other magnetic heads 16. In addition, if the number of magnetic heads 16 is an odd number, the magnetic head 16 arranged in the center of the stacking direction is equivalent to the central head. In addition, the magnetic head 16a is the outermost magnetic head 16 located on the substrate side in the stacking direction, and the magnetic head 16r is the outermost magnetic head 16 located on the cover side in the stacking direction. Hereinafter, these magnetic heads 16a and 16r located on the outermost layer are appropriately referred to as external heads to distinguish them from other magnetic heads 16.

[0061] Among the 18 magnetic heads 16 , the width WP of the main magnetic pole 60 of the write head 58 is larger in the outer magnetic heads 16 as they are farther away from the vicinity of the center in the stacking direction. Figure 8 16a to 16r is a diagram showing an example of the value of the width WP (write core width) of the main magnetic pole 60 of the write head 58. Figure 8 In the figure, Head No. 1 corresponds to head 16a, and in ascending order, Head No. 18 corresponds to head 16r.

[0062] like Figure 8 As shown, regarding the width WP of the main magnetic pole 60, the magnetic heads 16i and 16j, which are the center heads, are the narrowest (smallest), and the magnetic heads 16 located closer to the outer layer relative to the center head in the stacking direction gradually become wider, and the magnetic heads 16a and 16r, which are the outer heads, are the widest (largest). Figure 8 In the example shown, the change amount of the width WP (write core width) is set to 1 nm units, but the change amount is not limited to this. In addition, the change amount may not be the same, and the change amount of the width WP may be varied from the center head to the outer head.

[0063] Here, for example, the wider the width WP of the main magnetic pole 60 is, the easier it is to increase the write diffusion (write penetration) to the adjacent tracks caused by repeated recording (writing) on ​​the magnetic disk 12. Therefore, for example, it is necessary to make adjustments such as setting the track width larger. In addition, the closer to the base side and the cover side of the frame 11, that is, the closer to the two sides (outermost side) in the stacking direction, the easier it is for the positioning accuracy of the magnetic head 16 to deteriorate. In this case, the magnetic disk 12 on the outer side in the stacking direction with relatively lower positioning accuracy is more likely to exceed the adjacent track and be recorded in a single recording (writing) operation, and therefore, it is necessary to set the track pitch to be wider than the track pitch of the magnetic disk 12 on the inner side with relatively higher positioning accuracy.

[0064] In contrast, in the present embodiment, instead of adjusting the track pitch, the width WP of the main magnetic pole 60 is narrowed as the center head is closer, and the width WP of the main magnetic pole 60 is widened as the outer head is closer. Therefore, even in the case where the positioning accuracy of the outer head is worse than that of the center head, the recording capacity of the magnetic disk 12 can be increased. In addition, since the magnetic heads 16 having different widths WP of the main magnetic pole 60 are mixed in one HDD 10, it is possible to seek to improve the yield of the magnetic heads 16.

[0065] In this way, instead of narrowing the width WP of the main magnetic pole 60 as the center head increases and widening the width WP of the main magnetic pole 60 as the outer head increases, the recording capacity of the magnetic disk 12 can also be increased in the same manner by narrowing the width of the magnetic characteristic of the main magnetic pole 60 as the center head increases and widening the width of the magnetic characteristic of the main magnetic pole 60 as the outer head increases. That is, in this case, the head 16 having the wider width of the magnetic characteristic of the main magnetic pole 60 is arranged in the outer layer farther from the center in the stacking direction (the outer position farther from the center in the parallel direction). For example, regarding the width of the magnetic characteristic of the main magnetic pole 60, the heads 16i and 16j as the center head are the narrowest (smaller), and the heads 16 located closer to the outer layer side relative to the center head in the stacking direction gradually become wider, and the heads 16a and 16r as the outer heads are the widest (larger). The amount of change in the width of the magnetic characteristic may not be the same, and the amount of change may be changed from the center head to the outer head.

[0066] The width of the magnetic characteristic of the main magnetic pole 60 is the width of the recording area in the cross-track direction WT, which allows the magnetic characteristic of the recording area to be properly read by the read head 54 when the recording track is magnetically recorded by the magnetic head 16, specifically, the write head 58. Fig. 9 As shown, for example, after measuring the off-track profile of the recording signal output when the bias voltage of STO65 is turned off, it is defined as its half-width (50% position) and the like. Fig. 9The cross-track position and the signal output values ​​shown are just examples and are not limited to these.

[0067] Next, HDDs involved in other embodiments are described. In addition, in the other embodiments described below, the basic structure is the same as that of the first embodiment described above. Therefore, the characteristic structures of the other embodiments different from the first embodiment are described below, and the description of the same components is omitted with reference to the corresponding drawings in the first embodiment.

[0068] (Second embodiment)

[0069] In the second embodiment, the working performance of the magnetic head 16 is tested before being assembled to the HDD 10, and the magnetic head 16 is classified into a plurality of groups according to the test results. In the present embodiment, the error rate of the magnetic head 16 is detected. The error rate is the ratio of the recording pattern that exceeds the recording track adjacent to the recording track (hereinafter referred to as the adjacent recording track) and is recorded in a recording (writing) operation of the recording track of the magnetic disk 12 by the write head 58.

[0070] Fig.10 This is a diagram schematically showing the relationship between the number of writes (Write count) and the error rate (Error Rate) for adjacent recording tracks. Fig.10 The magnetic head 16 is classified into three groups A, B, and C, and the relationship between the number of recording times for adjacent recording tracks in each group and the error rate after the number of recording times is schematically shown. Fig.10 In the example shown, the error rate deteriorates in the order of group A, group B, and group C. Specifically, as the number of recordings increases, for example, when the number of recordings exceeds N, the error rate of group B deteriorates significantly compared to group A, and further, the error rate of group C deteriorates significantly compared to group B.

[0071] In this embodiment, among the multiple groups obtained by classifying the heads 16 according to the error rate, the group to which the heads 16 with higher error rates belong is arranged in the outer layer farther away from the center in the stacking direction (the outer position farther away from the center in the parallel direction).

[0072] Here, if Figure 7 As shown in FIG. 1 , it is assumed that 18 magnetic heads 16a to 16r are arranged. In this case, these magnetic heads 16a to 16r are classified into a plurality of groups of a predetermined number according to the error rate. As an example, the 18 magnetic heads 16a to 16r are classified into groups of 6 at a time. Fig.10The corresponding three groups are A, B, and C. Specifically, the magnetic heads 16g, 16h, 16i, 16j, 16k, and 16l belong to group A. The magnetic heads 16d, 16e, 16f, 16m, 16n, and 16o belong to group B. The magnetic heads 16a, 16b, 16c, 16p, 16q, and 16r belong to group C.

[0073] Therefore, in Figure 7 In the illustrated example, six magnetic heads 16g to 16l belonging to group A with the lowest error rate are arranged near the center in the stacking direction. Three magnetic heads 16 belonging to group B with the second lowest error rate than group A are arranged on the base side (positions of magnetic heads 16d, 16e, and 16f) and cover side (positions of magnetic heads 16m, 16n, and 16o) of these magnetic heads 16. Furthermore, three magnetic heads 16 belonging to group C are arranged on the base side (positions of magnetic heads 16a, 16b, and 16c) and cover side (positions of magnetic heads 16p, 16q, and 16r) of these magnetic heads 16.

[0074] Thus, the error rate of the magnetic head 16 becomes higher by group from the central head to the external head in the stacking direction. In addition, the number of groups that the magnetic head 16 is classified is not limited to 3, and can be 2 or more than 4. Here, about the magnetic heads 16 arranged in the stacking direction, the more external heads, the easier it is to deteriorate the positioning accuracy, and it is preferred to widen the spacing (track spacing) of the recording tracks. On the other hand, corresponding to the need to widen the track spacing, the more external heads, the more the edge characteristics can be relaxed (error rate degradation when magnetic recording is performed to adjacent recording tracks). In addition, the magnetic head 16 with a high error rate can also improve the linear recording density and reduce the track spacing density. Therefore, in the present embodiment, instead of adjusting the track spacing, the group of magnetic heads 16 with a higher error rate is configured in the outer layer farther away from the center of the stacking direction. Therefore, the recording capacity of the magnetic disk 12 can be increased.

[0075] (Third embodiment)

[0076] In the third embodiment, the working performance of the magnetic disk 12 is tested before being assembled into the HDD 10, and the magnetic disk 12 is classified into a plurality of groups according to the test results. In the present embodiment, an index value representing the overwrite characteristic (OW) of the magnetic disk 12 is detected. The overwrite characteristic is indexed by the amplitude difference of the recording pattern before and after overwriting when a recording pattern of a certain frequency is overwritten with a recording pattern of a frequency different from the recording pattern, and the quality (writing difficulty) is determined according to the value. For example, in the case of perpendicular magnetic recording, a low-frequency signal is more difficult to write than a high-frequency signal. Therefore, the value obtained by expressing the signal that does not completely disappear when a low-frequency signal is written after a high-frequency signal is written in dB can be used as an index of the overwrite characteristic.

[0077] Fig.11 FIG. 2 is a diagram showing an example of a case where the magnetic disks 12 are classified based on such overwrite characteristics (OW). Fig.11 In the example shown, the disks 12 are classified into five groups according to the range of the overwrite characteristic value, that is, the degree of writing difficulty. In this case, Gr1 is the group to which the disks 12 that are most difficult to be overwritten belong, and Gr5 is the group to which the disks 12 that are most easily overwritten belong in ascending order. Fig.11 The threshold value between groups shown is an example and is not limited to the value shown in the figure, and can be set arbitrarily.

[0078] In this embodiment, among the multiple groups obtained by classifying the disks 12 according to the overwrite characteristics (OW), the group to which the disks 12 with higher overwrite characteristics belong is arranged in the outer layer farther away from the center in the stacking direction (the outer position farther away from the center in the parallel direction).

[0079] Here, if Figure 7 As shown in FIG. 1 , it is assumed that nine disks 12a to 12i are arranged. In this case, the disks 12a to 12i are classified into a plurality of groups for each predetermined number of disks according to the overwriting characteristics. As an example, the nine disks 12a to 12i are classified into groups corresponding to Fig.11 There are five corresponding groups (Gr1 to Gr5). Specifically, disk 12e belongs to Gr1 (20≤OW<23). Similarly, disks 12d and 12f belong to Gr2 (23≤OW<26), disks 12c and 12g belong to Gr3 (26≤OW<29), disks 12b and 12h belong to Gr4 (29≤OW<32), and disks 12a and 12i belong to Gr5 (32≤OW<35).

[0080] Therefore, in Figure 7 In the illustrated embodiment, the disk 12e belonging to Gr1 with the lowest overwriting characteristic is arranged near the center in the stacking direction. The disks 12 belonging to Gr2, Gr3, and Gr4 with higher overwriting characteristics than Gr1 are arranged on the base side and the cover side of the disk 12e, respectively. Furthermore, the disks 12a and 12i belonging to Gr5 with the highest overwriting characteristic are arranged at the outermost layers in the stacking direction, respectively.

[0081] Thus, the overwrite characteristic of magnetic disk 12 becomes higher by group from near the center to the outermost layer in the stacking direction.Therefore, for example, different from the first embodiment and the second embodiment mentioned above, even when the width WP of the main magnetic pole 60 of magnetic head 16 is roughly the same or when the error rate is roughly the same, the recording capacity of magnetic disk 12 can be increased.

[0082] (Fourth embodiment)

[0083] In the fourth embodiment, the head amplifier IC30 makes different recording currents used to excite the main magnetic pole 60 according to the position of the magnetic head 16 (write head 58) in the stacking direction. Specifically, when magnetic recording (writing data) is performed on the magnetic disk 12, the recording current supplied from the recording current supply circuit (recording current supply unit) 91 to the first recording coil 70 and the second recording coil 72 is controlled by the main controller 90.

[0084] Fig.12 FIG. 4 is a flowchart showing an example of control of the recording current (recording current control processing) performed by the main controller 90. Fig.12 As shown, when writing data to the magnetic disk 12, the main controller 90 receives a write command instructing to write data to the magnetic disk 12 from the host 95 (ST1).

[0085] When receiving a write command, the main controller 90 selects a writing destination for the data, and determines the recording track of the magnetic disk 12 to which the data is to be written based on servo information, etc. Thus, the main controller 90 determines the position of the magnetic head 16 in the stacking direction (parallel direction) for writing (magnetically recording) data to the determined recording track (ST2).

[0086] Next, the main controller 90 writes data to the magnetic disk 12 that has been determined as the writing destination of the data. Specifically, the HDC 96 causes the head amplifier IC 30 to perform signal processing of the data via the R / W channel 94. At this time, the head amplifier IC 30 changes the magnitude of the recording current supplied from the recording current supply circuit 91 to the first recording coil 70 and the second recording coil 72 according to the position of the magnetic head 16 (write head 58) in the stacking direction. As a result, the main magnetic pole 60 is excited, and the amount of magnetic flux flowing in the main magnetic pole 60 changes. For example, a predetermined table is stored in the memory 80 of the main controller 90, and the predetermined table associates the relationship between the position of the magnetic head 16 (write head 58) in the stacking direction and the value of the optimal recording current at the position. When controlling the recording current, the MPU 97 sets the value of the optimal recording current at the position of the magnetic head 16 (write head 58) in the stacking direction according to the table, and gives it to the head amplifier IC 30 as a parameter.

[0087] In the present embodiment, the recording current supply circuit 91 increases (increases) the recording current for exciting the main magnetic pole 60 more (ST3) for the magnetic head 16 (external head) arranged on the outer side of the stacking direction (the outer position in the parallel direction) than for the magnetic head 16 (central head) arranged near the center in the stacking direction (parallel direction). Increasing the recording current for exciting the main magnetic pole 60 achieves the same effect as widening the width WP of the main magnetic pole 60. Therefore, the recording current for exciting the main magnetic pole 60 is increased more for the outer head than for the central head, thereby achieving the same effect as widening the width WP of the main magnetic pole 60 relative to the central head.

[0088] Thus, for example, unlike the first and second embodiments described above, even when the width WP of the main magnetic pole 60 of the magnetic head 16 is substantially the same, or when the error rate is substantially the same, the recording capacity of the magnetic disk 12 can be increased. In addition, for example, unlike the third embodiment described above, even when the overwrite characteristics (OW) of the magnetic disk 12 are substantially the same, the recording capacity of the magnetic disk 12 can be increased.

[0089] Several embodiments of the present invention have been described above, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: A plurality of magnetic disks having recording layers, arranged on the same axis with intervals therebetween; and A plurality of magnetic heads having magnetic poles for generating a recording magnetic field in a perpendicular direction to the recording layer are arranged at intervals along the parallel direction of the magnetic disks. Among a plurality of groups obtained by classifying the magnetic disks according to index values ​​indicating overwriting characteristics of the magnetic disks, the group to which the magnetic disks having higher index values ​​belong is arranged at an outer position farther from the center in the parallel direction.

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