JP2008171490A - Perpendicular recording discrete track medium and servo pattern magnetization method thereof - Google Patents

Abstract

A servo pattern magnetizing method having servo signals of both amplitudes for eliminating the need for intensity change and waveform shaping during servo signal reproduction, improving head positioning accuracy, and improving track recording density. Provided.
A servo pattern magnetization method for a perpendicular recording discrete track medium using a master disk, wherein a magnetic field leaks from a soft magnetic layer provided on the master disk at a position corresponding to the servo pattern, and is applied to a servo area. A servo pattern magnetization method comprising a step of transferring a servo signal composed of a pair of two types of magnetizations which are perpendicular and opposite to each other.
[Selection] Figure 4

Description

  The present invention relates to a perpendicular recording discrete track medium and a servo pattern magnetization method thereof.

  Since 1997, the recording density of HDDs has increased rapidly at an annual rate of 60-100%. As a result of such remarkable growth, the in-plane recording method used so far is approaching the limit of higher density. Under such circumstances, in recent years, a perpendicular recording method capable of increasing the density has attracted attention, and research and development has been actively conducted. Finally, in 2005, the commercialization of HDDs that adopted the perpendicular recording method for some models began.

  A perpendicular magnetic recording medium mainly includes a magnetic recording layer of a hard magnetic material, an underlayer for orienting the magnetic recording layer in a desired direction, a protective film for protecting the surface of the magnetic recording layer, and a magnetic recording layer. It is composed of a soft magnetic layer that plays a role of concentrating a magnetic flux generated by a magnetic head used for recording.

  For the purpose of further improving the recording density of the perpendicular magnetic recording medium, research and development of discrete track media in which a plurality of recording tracks are magnetically separated have been performed. FIG. 6A shows a schematic top view of a conventional discrete track medium. The discrete track medium 500 includes a sector 530 having a recording area 510 having a plurality of recording tracks for recording data and a servo area 520 having a servo pattern for detecting the position in the width direction of each track. A plurality of substrates are formed by dividing the circumferential direction on a substrate. FIG. 6B is a diagram illustrating the structure of the recording area 510 and the servo area 520 by enlarging and linearly extending a partial area 540 of the sector 530 of the discrete track medium. Each of the plurality of recording tracks 512 in the recording area 510 and the plurality of servo blocks 522 carrying the position information of each track in the servo area 520 are formed as physical irregularities. Here, the plurality of tracks 512 and the plurality of servo blocks 522 are formed by etching the magnetic recording layer using a lithography technique. Each of the plurality of tracks 512 forms a concentric track 514 by combining the tracks 512 located at an equal distance from the media center. Each of the plurality of tracks 512 is magnetically separated from the adjacent tracks 512 by physical unevenness existing between the adjacent tracks 512, and the magnetic interference between them is reduced.

  An example of a servo pattern magnetization method for a discrete track medium of the prior art is shown in FIG. A discrete track medium generally has a structure including at least a nonmagnetic substrate 610, a soft magnetic layer 620, and a magnetic recording layer 630 divided into a plurality of portions. As shown in FIG. 7A, the servo pattern is magnetized by applying a single pole head 550 that applies a magnetic field in the direction perpendicular to the substrate (here, an example in which the S pole faces the discrete track medium) to the discrete track medium. It is arranged near the magnetic recording layer 630 of the medium and moved in the circumferential direction (track direction). The magnetization obtained by this process is shown in FIG. Magnetization in one direction (here, upward) in the direction perpendicular to the substrate is imparted to both the magnetic recording layers 630s (servo block 522) and 630r (track 512).

  Next, in the information recording process for the discrete track medium, as shown in FIG. 7C, the single-pole head 560 is used to change the perpendicular magnetization (both upward and downward) according to the information to the magnetic recording layer 630r (track). 512). Next, FIG. 7D shows a signal when the magnetization of the magnetic recording layer 630 is read using the reproducing head. As clearly shown in FIG. 7D, the data signal in the recording area 510 has both amplitudes, whereas the servo signal in the servo area 520 has one amplitude.

  When the servo signal has a single amplitude, the signal intensity is less than half. As a result, the head positioning accuracy deteriorates and it becomes difficult to increase the track recording density. Further, since the data signal has both amplitudes, it is necessary to change the signal intensity and / or shape the waveform in accordance with the servo signal reading and the data signal reading.

  To solve this problem, a servo pattern (position detection mark) arranged in the servo zone is composed of a magnetic recording block area capable of recording a plurality of bits, and servo signals (both amplitudes) (in the magnetic recording block area) A method of recording a magnetization reversal signal has been proposed (see Patent Document 1). In addition, a method using a perpendicular magnetic recording layer having two types of regions having different coercive forces in the servo signal region has been proposed (see Patent Document 2). In this method, a perpendicular magnetic field having a sufficient strength is first applied to magnetize two regions in the perpendicular magnetic recording layer in one direction. Next, by applying a perpendicular magnetic field in the opposite direction of the strength to reverse only one magnetization of the two types of regions, only one magnetization of the two types of regions is inverted, and a servo that records servo signals of both amplitudes. A signal area is formed.

  Further, in a longitudinal magnetic recording medium having two magnetic recording layers, a master disk having a soft magnetic layer in a portion corresponding to a servo pattern (position detection mark) is used, and the longitudinal magnetic recording medium has a longitudinal direction due to magnetic flux concentration on the soft magnetic layer. There has been proposed formation of a servo pattern by transfer to each of two magnetic recording layers due to a change in magnetic field strength (see Patent Document 3).

JP 2004-110896 A JP 2003-016623 A JP 2003-162815 A

  An object of the present invention is to provide a method for magnetizing a servo pattern including servo signals of both amplitudes using a simpler process.

The perpendicular recording discrete track medium of the present invention is
A recording area having a plurality of recording tracks, and a plurality of servo areas for recording servo signals for detecting the position in the width direction of each track;
Each of the plurality of tracks is a soft magnetic layer formed on the substrate separately from other tracks, and formed on the soft magnetic layer separately from other tracks, and has an easy axis of magnetization perpendicular to the substrate surface. A magnetic recording layer having
The servo area includes a soft magnetic layer formed as an integral continuous layer on the substrate, and a magnetic recording layer formed as an integral continuous layer on the soft magnetic layer and having an easy axis of magnetization perpendicular to the substrate surface; Including
Servo signals composed of a plurality of sets having two kinds of magnetizations perpendicular to the substrate and opposite to each other are recorded in the servo area.

Servo pattern magnetization method of perpendicular recording discrete track media of the present invention,
A perpendicular recording discrete track medium comprising a recording area having a plurality of recording tracks, and a servo area for recording a servo signal for detecting the position in the width direction of each track, each of the plurality of tracks on a substrate A soft magnetic layer formed separately from other tracks, and a magnetic recording layer formed on the soft magnetic layer separately from other tracks and having an easy axis of magnetization perpendicular to the substrate surface, The servo area includes a soft magnetic layer formed as an integral continuous layer on the substrate, and a magnetic recording layer formed as an integral continuous layer on the soft magnetic layer and having an axis of easy magnetization perpendicular to the substrate surface. Preparing a perpendicular recording discrete track media including:
A master disk having a support and a servo pattern embedding area in which a servo pattern made of a soft magnetic layer is embedded in the support, the servo pattern embedding area at a position corresponding to a servo area of a perpendicular recording discrete track medium Preparing a master disk including a soft magnetic layer formed and embedded in a servo pattern on a support at a position where a servo signal is to be recorded;
Recording a servo signal by applying a magnetic field from above the master disk and transferring a servo pattern to a servo area of a perpendicular recording discrete track medium by a leakage magnetic field from the soft magnetic layer. It consists of a plurality of sets having two kinds of magnetizations perpendicular to and opposite to each other. Here, the applied magnetic field is desirably a uniform magnetic field in the track extending direction. The servo pattern embedding area desirably has a width of 80% or more of the width of the servo area at the corresponding position.

  With the above configuration, it is possible to record servo signals of both amplitudes in the servo area by transferring the soft magnetic layer pattern in the servo pattern embedding area of the master disk to the servo area of the perpendicular recording discrete track media. It becomes. As a result, it is possible to eliminate the necessity of intensity change and waveform shaping when the servo signal is reproduced. Further, the perpendicular recording discrete track medium of the present invention has further effects of improving the head positioning accuracy and improving the track recording density. Furthermore, servo pattern transfer, that is, servo signal recording of both amplitudes can be efficiently performed in a single step of applying a uniform magnetic field in the circumferential direction.

  FIG. 1A shows a schematic top view of a perpendicular recording discrete track medium of the present invention. A perpendicular recording discrete track medium 100 according to an embodiment of the present invention includes a sector 130 including a recording area 120 having a plurality of recording tracks and a servo area 110 for recording a servo signal for detecting the position in the width direction of each track. However, it is formed by dividing the circumferential direction on a disk-shaped substrate. FIG. 1B is a diagram illustrating the structure of the recording area 120 and the servo area 110 by enlarging and linearly extending a partial area 140 of the sector 130. FIG. 2 shows a cross-sectional structure of the perpendicular recording discrete track medium of the present invention. 2A is a cross-sectional view along the circumference of a position corresponding to one track, FIG. 2B is a cross-sectional view taken along a cutting line 2b-2b, and FIG. 2C is a cutting line. It is sectional drawing in 2c-2c.

  Each of the plurality of recording areas 120 of the perpendicular recording discrete track medium of the present invention includes a plurality of tracks 122. A plurality of tracks 122 located equidistant from the center of the media are combined to form a concentric track 114. Each of the plurality of tracks 122 includes a soft magnetic layer 20r formed on the substrate 10 independently of other tracks and a magnetic recording layer 30r formed independently of other tracks. That is, the soft magnetic layer 20r and the magnetic recording layer 30r constituting one track 122 are formed separately from the magnetic recording layer of the adjacent sector 122 in the same recording area, and the same track in the adjacent recording area. Are separated from each other by a servo area 110.

  Each of the plurality of servo areas 110 of the perpendicular recording discrete track medium of the present invention includes a soft magnetic layer 20s formed as an integral continuous layer on the substrate 10 and a magnetic recording layer 30s formed as an integral continuous layer. Is done. That is, each of the plurality of servo areas 110 records a plurality of servo signals composed of a pair of magnetizations in two kinds of directions perpendicular to the substrate and opposite to each other.

  The substrate 10 is nonmagnetic and has a flat surface. The substrate 10 can be formed using any material known in the art. For example, the substrate 10 can be formed using an Al alloy plated with NiP, tempered glass, or crystallized glass used for a magnetic recording medium.

  The soft magnetic layer 20 (r, s) is made of a crystalline material such as FeTaC or Sendust (FeSiAl) alloy; a microcrystalline material such as FeTaC, CoFeNi, or CoNiP; or an amorphous material containing a Co alloy such as CoZrNb or CoTaZr. Can be used. The optimum value of the thickness of the soft magnetic layer 20 (r, s) varies depending on the structure and characteristics of the magnetic head used for recording, but is preferably about 10 nm to 500 nm in view of productivity. . A nonmagnetic underlayer formed using a nonmagnetic material containing Cr such as Ti or TiCr alloy may be provided between the soft magnetic layer 20 (r, s) and the substrate.

  The magnetic recording layer 30 (r, s) can be preferably formed using a ferromagnetic material of an alloy containing at least Co and Pt. Further, in order to obtain a discrete track medium for performing perpendicular magnetic recording, the easy axis of magnetization of the material of the magnetic recording layer 30 (r, s) (the c axis of the hexagonal close-packed (hcp) structure) is the surface of the substrate 10. It is necessary to be oriented in the vertical direction. The magnetic recording layer 30 (r, s) can be formed using an alloy material such as CoPt, CoCrPt, CoCrPtB, or CoCrPtTa. The film thickness of the magnetic recording layer 30 (r, s) is not particularly limited. However, from the viewpoint of improving productivity and recording density, the magnetic recording layer 30 (r, s) preferably has a thickness of 30 nm or less, more preferably 15 nm or less.

  Optionally, a seed layer may be provided between the soft magnetic layer 20 and the magnetic recording layer 30 (r, s) to improve the crystal orientation of the magnetic recording layer material. The seed layer is made of a permalloy material such as NiFeAl, NiFeSi, NiFeNb, NiFeB, NiFeNbB, NiFeMo, NiFeCr; a material obtained by further adding Co to a permalloy material such as CoNiFe, CoNiFeSi, CoNiFeB, CoNiFeNb; Co; or It can be formed using a Co-based alloy such as CoB, CoSi, CoNi, CoFe. The seed layer desirably has a film thickness sufficient to control the crystal structure of the magnetic recording layer 30 (r, s). In general, the seed layer desirably has a film thickness of 3 nm to 50 nm.

  The soft magnetic layer 20, the magnetic recording layer 30 (r, s), and the optional nonmagnetic underlayer and seed layer are formed by sputtering (including DC magnetron sputtering, RF magnetron sputtering, etc.), vacuum deposition Any method known in the art, such as a method, can be used.

  Patterning for forming the plurality of tracks 122 can be performed using a photolithography method. For example, a mask having a required pattern is formed using a resist, and the soft magnetic layer 20, the magnetic layer 20 is magnetically bonded using any means known in the art such as wet etching, sputter etching, plasma etching, and reactive ion etching. The recording layer 30 (r, s), and the optional nonmagnetic underlayer and seed layer may be etched. After the etching is finished, the mask is removed by cleaning with a solvent, plasma ashing, or the like, so that a plurality of sectors 122 can be obtained.

  Optionally, a protective layer and / or a liquid lubricant layer may be provided on the magnetic recording layer 30 (r, s). The protective layer is a layer for protecting each constituent layer below the magnetic recording layer 30 (r, s), and for example, a thin film mainly composed of carbon can be used. In addition, the protective layer may be formed using various thin film materials known in the art as materials for a magnetic recording medium protective film. The protective layer can be generally formed using a sputtering method (including a DC magnetron sputtering method, an RF magnetron sputtering method, etc.), a vacuum deposition method, a CVD method, or the like. The liquid lubricant layer is a layer for providing lubrication when the recording / reading head is in contact with the perpendicular recording discrete track medium. For example, a perfluoropolyether liquid lubricant, It can be formed using a variety of liquid lubricant materials known in the art. The liquid lubricant layer can be formed using any coating method known in the art such as a dip coating method or a spin coating method.

  Next, positional information of the track 122 in the recording area 120 (for example, information indicating the sector 130 to which the track 122 belongs, information on the track 122 in the sector 130, etc.) in the plurality of servo areas 110 of the perpendicular recording discrete track medium of the present invention. A master disk 200 used when recording a servo signal for indicating position information) will be described. As shown in FIG. 3A, the master disk 200 according to the embodiment includes a plurality of servo pattern embedding areas 210 at positions corresponding to the plurality of servo areas 110 of the discrete track medium 100, and the plurality of servo pattern embedding areas 210. And a free space 220 that is spaced apart. That is, the master disk has the same number of servo pattern embedding areas 210 as the plurality of servo areas 110 of the discrete track medium 100. In the present invention, each of the plurality of servo pattern embedding areas 210 preferably has a narrower width than the corresponding servo area 110. Preferably, the width of the servo pattern embedding area 210 is 80% or more of the width of the corresponding servo area 110. Since the servo band is increased by about 25% due to the amplitude doubling, the effective sampling rate can be increased by 25% accordingly. Therefore, even if the loss area is 20%, the servo signal density higher than that of the conventional method can be maintained.

  As shown in FIG. 3B, each of the plurality of servo pattern embedding areas 210 has a servo pattern 212 arranged at a position where a plurality of servo signals are to be recorded.

  FIG.3 (c) shows sectional drawing in the cutting | disconnection line 3c-3c of FIG.3 (b). The master disk 200 includes a support 40 and a plurality of soft magnetic layers 42 embedded in the support 40. The plurality of soft magnetic layers 42 are present in the servo pattern embedding region and constitute the servo pattern 212. The soft magnetic layer 42 does not exist in the empty area 220.

  The support 40 can be formed using any nonmagnetic material (for example, Si (including single crystal Si), Al alloy, glass (including tempered glass and crystallized glass), and the like). Each of the plurality of soft magnetic layers 42 includes an amorphous material including a Co alloy such as CoZrNb or CoTaZr; a crystalline material such as FeTaC or Sendust (FeSiAl) alloy; or a microcrystalline material such as FeTaC, CoFeNi, or CoNiP. The soft magnetic material can be used.

  The master disk 200 can be produced using any means known in the art. For example, a step of forming a resist mask having an opening corresponding to the servo pattern 212 on the support 40, a step of etching the support to form a recess at a position corresponding to the servo pattern 212, and soft magnetism The master disk 200 may be manufactured using a method including a step of depositing a material and a step of removing the resist mask and leaving a soft magnetic material only in the recess.

  Next, a servo pattern magnetization method according to the present invention for recording a servo signal in the servo area 110 of the perpendicular recording discrete track medium 100 using the master disk 200 will be described. First, as shown in FIG. 4A, the perpendicular recording discrete track medium 100 is arranged to face the master disk 200. At this time, the servo pattern embedding area 210 and the servo area 110 are arranged so that each of the corresponding servo pattern embedding areas 210 of the master disk 200 falls within the corresponding servo area 110 of the perpendicular recording discrete track medium 100. Are placed facing each other. At this time, the recording area 120 is arranged to face the empty area 220.

  Next, a ring magnet 50 that generates a magnetic field in the media circumferential direction (that is, the direction in which the track 122 extends) is disposed immediately above the master disk 200, and the ring magnet 50 is moved relative to the media. Here, the ring magnet 50 may be fixed and the medium may be rotated, or the medium may be fixed and the ring magnet 50 may be moved in the circumferential direction. Since the soft magnetic layer 42 is discontinuously present in the servo pattern embedding region 210 (servo region 110), the magnetic flux 52 generated by the ring magnet 50 in the portion where the soft magnetic layer 42 is present is a soft magnetic material having a high magnetic permeability. Concentrate on layer 42. At that time, a leakage magnetic field having a vertical component is generated in the magnetic recording layer near both edges of the soft magnetic layer 42 due to the concentration of magnetic flux. In FIG. 4 (a), a right magnetic field is generated by the ring magnet 50. Therefore, a downward leakage magnetic field is generated in the magnetic recording layer 30s near the left edge of the soft magnetic layer 42, and an upward magnetic field is generated near the right edge. A leakage magnetic field is generated. With this leakage magnetic field, as shown in FIG. 4B, a plurality of servo signals composed of a pair of magnetizations in two directions perpendicular to the substrate and opposite to each other are recorded in the magnetic recording layer 30s. A servo pattern is formed. Since the soft magnetic layer 42 does not exist in the empty area 220, no signal is recorded on the plurality of tracks 122 in the recording area 120. After forming the servo pattern, the master disk is removed from the perpendicular recording discrete track medium 100.

  Recording / reproduction of the perpendicular recording discrete track medium on which the servo pattern is recorded as described above will be described with reference to FIG. As shown in FIG. 5A, upward and downward magnetization is recorded on the magnetic recording layer 30r of the track 122 in the recording area 120 according to the information to be recorded, using the single magnetic pole head 60. Next, FIG. 5B shows signals in the servo area 110 and the recording area 120 that are reproduced by a reproducing head (not shown) such as a GMR head. As apparent from FIG. 5B, since both directions (upward and downward) magnetization are recorded in both the servo area 110 and the recording area 120, servo signals with both amplitudes are obtained from the servo area 110, Both amplitude data signals are obtained from the recording area 120. Since signals having both amplitudes can be obtained from both regions, it is possible to eliminate the need for intensity change and waveform shaping during servo signal reproduction and data signal reproduction. Therefore, by using the perpendicular recording discrete track medium of the present invention, it is possible to improve the head positioning accuracy and improve the track recording density.

1A and 1B are views showing an embodiment of a perpendicular recording discrete track medium of the present invention, wherein FIG. 1A is a top view and FIG. 2B is an enlarged view showing a recording area and a servo area. It is sectional drawing which shows the perpendicular recording discrete track media of embodiment shown in FIG. 1 of this invention, (a) is sectional drawing along a periphery, (b) is sectional drawing cut | disconnected by the cutting line 2b-2b (C) is a cross-sectional view taken along the cutting line 2c-2c. It is a figure which shows the master disk used for the servo pattern magnetization method of the perpendicular recording discrete track media of embodiment of this invention shown in FIG. 1, (a) is a top view, (b) expands the area | region 240, and It is the expanded top view, (c) is sectional drawing cut | disconnected by the cutting line 3c-3c. It is a figure which shows the process of the servo pattern magnetization method of the perpendicular recording discrete track media of embodiment shown in FIG. 1 of this invention, (a) is a figure which shows a magnetization process, (b) shows the servo pattern obtained. FIG. It is a figure which shows the process of recording / reproduction | regeneration of the perpendicular recording discrete track media of embodiment shown in FIG. 1 of this invention, (a) is a figure which shows the time of recording, (b) is a figure which shows the time of reproduction | regeneration. . It is a figure which shows the conventional perpendicular recording discrete track media, (a) is a top view, (b) is an enlarged view which shows a recording area and a servo area. It is a figure which shows the process of the servo pattern magnetization method of the conventional perpendicular recording discrete track media, (a) is a figure which shows a magnetization process, (b) is a figure which shows the servo pattern obtained.

Explanation of symbols

10 substrate 20 (r, s), 42 soft magnetic layer 30 (r, s) magnetic recording layer 40 support 50 ring magnet 52 magnetic flux 60 single pole head 100 perpendicular recording discrete track media 110 servo area 114 concentric track 120 recording Area 122 Recording track 130 of each sector Sector 200 Master disk 210 Servo pattern embedding area 220 Free area

Claims (4)

A perpendicular recording discrete track medium comprising a recording area having a plurality of recording tracks and a servo area for recording a servo signal for detecting a position in the width direction of each track,
Each of the plurality of tracks is a soft magnetic layer formed on the substrate separately from other tracks, and formed on the soft magnetic layer separately from other tracks, and has an easy axis of magnetization perpendicular to the substrate surface. A magnetic recording layer having
The servo area includes a soft magnetic layer formed as an integral continuous layer on the substrate, and a magnetic recording layer formed as an integral continuous layer on the soft magnetic layer and having an easy axis of magnetization perpendicular to the substrate surface; Including
A perpendicular recording discrete track medium, wherein a servo signal comprising a plurality of sets having two kinds of magnetizations perpendicular to the substrate and opposite to each other is recorded in the servo area. A perpendicular recording discrete track medium comprising a recording area having a plurality of recording tracks and a plurality of servo areas for recording a servo signal for detecting the position in the width direction of each track, each of the plurality of tracks being A soft magnetic layer formed separately from other tracks on the substrate, and a magnetic recording layer formed separately from the other tracks on the soft magnetic layer and having an axis of easy magnetization perpendicular to the substrate surface. The servo area includes a soft magnetic layer formed as an integral continuous layer on the substrate, and a magnetic recording formed as an integral continuous layer on the soft magnetic layer and having an easy axis of magnetization perpendicular to the substrate surface. Providing a perpendicular recording discrete track media including a layer;
A master disk having a support and a servo pattern embedding area in which a servo pattern made of a soft magnetic layer is embedded in the support, the servo pattern embedding area at a position corresponding to a servo area of a perpendicular recording discrete track medium Preparing a master disk including a soft magnetic layer formed and embedded in a servo pattern on a support at a position where a servo signal is to be recorded;
Recording a servo signal by applying a magnetic field from above the master disk and transferring a servo pattern to a servo area of a perpendicular recording discrete track medium by a leakage magnetic field from the soft magnetic layer. A servo pattern magnetization method for perpendicular recording discrete track media, comprising a plurality of sets having two kinds of magnetizations perpendicular to and opposite to each other.   The servo pattern magnetization method according to claim 2, wherein the applied magnetic field is a uniform magnetic field in a direction in which the track extends.   3. The servo pattern magnetization method according to claim 2, wherein the servo pattern embedding area has a width of 80% or more of the width of the servo area at the corresponding position.

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