JP4413703B2 - Magnetic disk and magnetic disk device - Google Patents

Description

  The present invention relates to a discrete track type magnetic disk and a magnetic disk device having the magnetic disk.

  In recent years, in order to cope with further increase in the density of magnetic recording media, a discrete track medium in which adjacent recording tracks are separated by a groove or a guard band made of a nonmagnetic material to reduce magnetic interference between adjacent tracks. Has attracted attention. When manufacturing such a discrete track medium, a magnetic layer pattern can be formed by an imprint method using a stamper, and the magnetic layer corresponding to a signal in the servo area along with the recording track pattern by the imprint method. If this pattern is also formed, the servo track write process can be eliminated, leading to cost reduction.

Conventionally, there is a document that refers to a position detection mark (servo pattern) in a servo area for a discrete track medium (Patent Document 1). However, in the prior art, the quality of the reproduction signal on the discrete track medium has not been studied.
JP 2004-110896 A

  As a result of examining the cause of the reproduction error that may occur when the discrete track medium is reproduced, the present inventors have reached the following conclusion. In a magnetic disk apparatus using a floating magnetic head, the head flying height (flying height: FH) increases toward the outer peripheral side of the magnetic disk. This is because the peripheral speed of the magnetic disk is faster toward the outer periphery, and the air pressure received by the head slider is higher.

  By the way, in the data area of the discrete track medium, the pattern of the magnetic layer forming the recording track and the nonmagnetic portion separating the recording track are alternately formed in the radial direction. In such a discrete track medium, if the area ratio between the magnetic layer pattern and the nonmagnetic portion is uniform over the entire disk surface, a sufficient signal-to-noise ratio (SNR) cannot be obtained on the outer or inner circumference side, and reproduction is performed. It has been found to generate an error.

  An object of the present invention is to provide a discrete track type magnetic disk capable of suppressing a reproduction error, and a magnetic disk device having the magnetic disk.

A magnetic disk according to an aspect of the present invention includes a data area formed on a disk substrate including a magnetic layer pattern forming a recording track, a servo area including a magnetic layer pattern used as a servo signal, A nonmagnetic portion for separating the pattern of the magnetic layer, the width of the nonmagnetic portion in the data region is constant regardless of the radial position, and the pitch of the recording track in the data region is The area ratio is smaller than the inner peripheral side, and the area ratio between the pattern of the magnetic layer and the non-magnetic portion in the data region differs depending on the radial position.

  A magnetic disk device according to another aspect of the present invention includes the above magnetic disk and a floating magnetic head.

  According to the magnetic disk and the magnetic disk device according to the embodiment of the present invention, reproduction errors can be suppressed.

  FIG. 1 is a schematic plan view of a magnetic disk (discrete track medium) according to an embodiment of the present invention. On the magnetic disk 1, servo areas 2 including magnetic layer patterns used as servo signals and data areas 3 including magnetic layer patterns forming recording tracks are alternately formed along the circumferential direction. Yes. Although only eight servo areas 2 are shown in FIG. 1, there are actually a large number of servo areas such as 120. In FIG. 1, the servo area 2 is shown as having a linear shape in the radial direction. However, the servo area 2 may have an arc along the trajectory of the actuator arm that moves the head slider. . In the servo area 2 and the data area 3, the pattern of the magnetic layer is separated by a nonmagnetic portion. Here, the nonmagnetic portion may be air in a groove that separates the pattern of the magnetic layer, a carbon protective layer, or an insulating layer filled in the groove.

  In the embodiment of the present invention, according to the radial position of the data area 3, the data area 3 is divided into an inner data area 3i, an intermediate data area 3m, and an outer data area 3o. The area ratio between the pattern of the magnetic layer and the nonmagnetic part is made different. Here, an example is shown in which the data area 3 is divided into three according to the radial position, but the number of the data area 3 according to the radial position is not limited to three and may be two or more.

  With reference to FIG. 2, an example of the magnetic layer pattern formed on the surface of the magnetic disk 1 according to the embodiment of the present invention is shown. As shown in FIG. 2, servo areas 2 and data areas 3 are alternately formed along the circumferential direction. The servo area 2 includes areas such as a preamble portion 21, an address portion 22, and a burst portion 23, each formed by a magnetic layer pattern. In addition to these regions, a gap portion may be included, and the order and arrangement of the regions may be different. In the data area 3, recording tracks 31 made of magnetic layer patterns and guard bands 32 made of grooves are alternately formed along the radial direction.

  With reference to FIGS. 3 to 5, for the magnetic disk 1 according to the embodiment of the present invention, a method of changing the area ratio between the magnetic layer pattern 52 and the nonmagnetic portion according to the radial position will be exemplified. In order to simplify the explanation, in these drawings, only the disk substrate 51 and the magnetic layer pattern 52 thereon are shown.

In FIG. 3, the pitches of the recording tracks in the inner data area 3i, the intermediate data area 3m, and the outer data area 3o are made smaller on the outer circumference side than on the inner circumference side. That is, the relationship between the track pitches TP _i , TP _m and TP _o is set as TP _i > TP _m > TP _o . In this example, the width of the nonmagnetic portion (guard band) is made constant regardless of the radial position of the data area, and the recording track width is made smaller on the outer peripheral side than on the inner peripheral side. In this way, the area ratio of the magnetic layer pattern 52 to the nonmagnetic portion is set smaller on the outer peripheral side than on the inner peripheral side.

In FIG. 4, the pitch of the recording track in each of the inner circumference data area 3i, the intermediate data area 3m, and the outer circumference data area 3o is set larger on the outer circumference side than on the inner circumference side. That is, the track pitch TP _i, TP _m, the relation between TP _o, is set to _{TP i <TP m <TP o} . In this example, the width of the nonmagnetic portion (guard band) is made constant regardless of the radial position of the data area, and the recording track width is made larger on the outer peripheral side than on the inner peripheral side. In this way, the area ratio of the magnetic layer pattern 52 to the nonmagnetic portion is set larger on the outer peripheral side than on the inner peripheral side.

In FIG. 5, the recording track pitches in the inner data area 3i, the intermediate data area 3m, and the outer data area 3o are constant (TP _i = TP _m = TP _o ). On the other hand, the width of the nonmagnetic portion (guard band) is set larger on the outer peripheral side than on the inner peripheral side, and the area ratio of the magnetic layer pattern 52 to the nonmagnetic portion is set on the outer peripheral side than on the inner peripheral side. I try to make it smaller.

  Although not shown, contrary to FIG. 5, the area ratio of the magnetic layer pattern 52 to the nonmagnetic portion may be larger on the outer peripheral side than on the inner peripheral side.

  A magnetic recording apparatus according to an embodiment of the present invention will be described with reference to FIG. This magnetic recording apparatus includes a magnetic disk 71, a head slider 76 including a magnetic head, a head suspension assembly (suspension 75 and actuator arm 74) that supports the head slider 76, and a voice coil motor ( VCM) 77 and a circuit board.

  The magnetic disk 71 is attached to a spindle motor 72 and rotated, and various digital data are recorded by a perpendicular magnetic recording system. The magnetic head incorporated in the head slider 76 is a so-called composite head, and includes a single magnetic pole structure write head and a read head using a shield type MR reproducing element (GMR film, TMR film, etc.). A suspension 75 is held at one end of the actuator arm 74, and the head slider 76 is supported by the suspension 75 so as to face the magnetic disk 71. The actuator arm 74 is attached to the pivot 73. A voice coil motor (VCM) 77 is provided at the other end of the actuator arm 74. A head suspension assembly is driven by a voice coil motor (VCM) 77 to position the magnetic head at an arbitrary radial position of the magnetic disk 71. At this time, the head slider 76 and the magnetic head are flying above the magnetic disk 71. The circuit board includes a head IC, and generates a drive signal for a voice coil motor (VCM), a control signal for controlling reading and writing by the magnetic head, and the like.

  As shown in FIG. 3 or 5, when a magnetic disk in which the area ratio of the magnetic layer pattern 52 to the nonmagnetic portion is smaller on the outer peripheral side than on the inner peripheral side, the following effects are obtained. Is obtained. On the outer peripheral side, the peripheral speed of the disk is fast, but since the area ratio of the magnetic layer pattern 52 is relatively small, the pressure of the air received by the head slider from the magnetic layer pattern 52 becomes small. On the inner peripheral side, the peripheral speed of the disk is slow, but since the area ratio of the magnetic layer pattern 52 is relatively large, the pressure of the air received by the head slider from the magnetic layer pattern 52 increases. Therefore, the flying height (FH) of the magnetic head can be made uniform regardless of the radial position of the disk. Further, since the area ratio of the magnetic layer pattern 52 is relatively large on the inner peripheral side where the bit error rate (BER) is severe, the signal-to-noise ratio (SNR) can be reduced.

  As shown in FIG. 4, when a magnetic disk is used in which the area ratio of the magnetic layer pattern 52 to the nonmagnetic portion is smaller on the outer peripheral side than on the inner peripheral side, the following effects can be obtained. . On the outer peripheral side, the flying height (FH) of the magnetic head is high, but since the area ratio of the magnetic layer pattern 52 is relatively large and the amount of magnetization from the magnetic layer pattern 52 is large, signal noise can be reduced.

Example 1
A magnetic disk was manufactured by imprinting according to the steps shown in FIGS. 7A to 7F and FIGS. 8A to 8F. In this magnetic disk, the data area is in a radial position range of 4.8 mm to 10.2 mm, one track is composed of 120 sectors, and the capacity of one sector is 10,000 bits.

  In the present embodiment, the radial positions of the data area 3i on the inner circumference side, the intermediate data area 3m, and the data area 3o on the outer circumference side of the magnetic disk and the track pitch of each area are set as follows.

Radial position Track pitch inner circumference side 4.8mm to 6.6mm 250nm
Middle 6.6mm-8.4mm 225nm
Outer peripheral side: 8.4 mm to 10.2 mm 200 nm.

  The width of the nonmagnetic part (guard band) was 70 nm in any region. Therefore, this magnetic disk has a structure as shown in FIG. 3, and the area ratio of the magnetic layer pattern 52 / nonmagnetic portion on the outer peripheral side is smaller than that on the inner peripheral side.

Hereinafter, the method for manufacturing the magnetic disk of this embodiment will be described in more detail.
First, a stamper was produced by the method shown in FIGS.
As shown in FIG. 7A, a 6-inch diameter Si wafer 41 was prepared, and the surface thereof was treated with hexamethyldisilazane (HMDS). On the other hand, resist ZEP-520 manufactured by Nippon Zeon Co., Ltd. was diluted 2-fold with anisole and filtered through a 0.2 μm membrane filter. A resist solution was spin-coated on the Si wafer 41 and then pre-baked at 200 ° C. for 3 minutes to form a resist 42 having a thickness of about 0.1 μm.

  As shown in FIG. 7B, a desired pattern is directly formed on the resist 2 on the Si wafer 1 using an electron beam lithography apparatus having a ZrO / W thermal field emission type electron gun emitter under the condition of an acceleration voltage of 50 kV. Drawn. When writing, a signal source that generates signals in synchronism with signals for forming servo patterns, burst patterns, address patterns, track patterns, signals sent to the stage drive system of the drawing apparatus, and deflection control signals for electron beams was used. . During drawing, the stage was rotated at a linear velocity of 500 mm / s with CLV (Constant Linear Velocity), and the stage was also moved in the radial direction. Also, a concentric track area was drawn by deflecting the electron beam every rotation.

  As shown in FIG. 7C, the Si wafer 41 is immersed in ZED-N50 (manufactured by ZEON Corporation) for 90 seconds to develop the resist 42, and is then immersed in ZMD-B (manufactured by ZEON Corporation) for 90 seconds. The resist master 45 was prepared by rinsing and drying by air blow.

As shown in FIG. 7D, a conductive film 46 made of Ni was formed on the resist master 45 by sputtering. Specifically, after using pure nickel as a target and evacuating to 8 × 10 ⁻³ Pa, a DC power of 400 W was applied for 40 seconds in a chamber in which argon gas was introduced and the pressure was adjusted to 1 Pa. Sputtering was performed to form a conductive film 46 having a thickness of about 30 nm.

  As shown in FIG. 7 (E), the resist master 45 with the conductive film 46 is immersed in a nickel sulfamate plating solution (NS-160, Showa Chemical Co., Ltd.), Ni electroformed for 90 minutes, An electroformed film 47 having a thickness of about 300 μm was formed. The electroforming bath conditions are as follows.

Nickel sulfamate: 600 g / L
Boric acid: 40 g / L
Surfactant (sodium lauryl sulfate): 0.15 g / L
Liquid temperature: 55 ° C
pH: 4.0
Current density: 20 A / dm ² .

  As shown in FIG. 7F, the electroformed film 47 and the conductive film 46 were peeled off from the resist master 45 with a resist residue attached. Resist residues were removed by oxygen plasma ashing. Specifically, plasma ashing was performed for 20 minutes by applying a power of 100 W in a chamber in which oxygen gas was introduced at 100 ml / min and the pressure was adjusted to 4 Pa. A father stamper including the conductive film 46 and the electroformed film 47 was obtained. Thereafter, an imprint stamper 48 was obtained by punching unnecessary portions of the father stamper with a metal blade.

Next, a magnetic disk was manufactured by the method shown in FIGS.
As shown in FIG. 8A, the stamper 48 was ultrasonically cleaned with acetone for 15 minutes. In order to improve the releasability during imprinting, the stamper 48 was subjected to the following treatment. A solution was prepared by diluting fluoroalkylsilane [CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OMe) ₃ ] (GE Toshiba Silicone Co., Ltd., TSL8233) to 5% with ethanol. The stamper 48 was immersed in this solution for 30 minutes, the solution was blown off with a blower, and annealed at 120 ° C. for 1 hour.

  On the other hand, a magnetic recording layer 52 was formed by sputtering on a disk substrate 51 made of 0.85 inch diameter donut glass. A resist 55 (manufactured by Rohm and Haas, S1801) was spin-coated on the magnetic recording layer 52 at a rotational speed of 3800 rpm.

  As shown in FIG. 8B, the stamper 48 was pressed against the resist 55 on the surface of the disk substrate 51 and pressed at 2000 bar for 1 minute to transfer the pattern of the stamper 48 to the resist 55. The resist 55 to which the pattern was transferred was irradiated with UV for 5 minutes and then baked at 160 ° C. for 30 minutes. In the unevenness formation process by imprinting, a resist residue remains on the bottom of the pattern recess.

  Using the 1000th imprinted disk substrate, the ICP (inductively coupled plasma) etching device removes the resist residue at the bottom of the pattern recess by RIE using oxygen gas at 2 mTorr as shown in FIG. 8C. Subsequently, as shown in FIG. 8D, the magnetic recording layer 52 was etched by Ar ion milling using the pattern of the resist 55 as a mask. As shown in FIG. 8E, the pattern of the resist 55 was peeled off by oxygen RIE at 400 W and 1 Torr. As shown in FIG. 8F, a protective layer 53 made of about 3 nm of diamond-like carbon (DLC) was formed on the entire surface by CVD (chemical vapor deposition). Thereafter, a lubricant having a thickness of about 1 nm was applied to the produced magnetic disk by a dip method.

  A magnetic recording apparatus as shown in FIG. 6 was manufactured using the manufactured magnetic disk, and a magnetic head flying test was performed by rotating the magnetic disk. As a result, flying height data as shown in FIG. 9 was obtained. As shown in this figure, the flying height of the magnetic head was almost constant regardless of the radial position of the disk. Also, the magnetic signal could be reproduced satisfactorily on the entire disk surface.

  As a reference example, a magnetic recording apparatus as shown in FIG. 6 was manufactured using a conventional in-plane recording medium that is not a discrete type, and a magnetic head flying test was performed by rotating the magnetic disk. As a result, flying height data as shown in FIG. 10 was obtained. In this case, the flying height increases toward the outer peripheral side of the magnetic disk.

  For comparison, a magnetic disk having a track pitch of 200 nm and a nonmagnetic portion (guard band) width of 70 nm in all data regions having a radial position of 4.8 mm to 10.2 mm was manufactured. The magnetic head was levitated to reproduce the magnetic signal. As a result, a reproduction error occurred in the inner periphery, and reproduction was impossible.

(Example 2)
According to the same process as in the first embodiment, a magnetic disk in which the data area is in the radius range of 4.8 mm to 10.2 mm, one track is composed of 120 sectors, and the capacity of one sector is 10,000 bits is imprinted. It was produced by the method.

  In the present embodiment, the radial positions of the data area 3i on the inner circumference side, the intermediate data area 3m, and the data area 3o on the outer circumference side of the magnetic disk and the track pitch of each area are set as follows.

Radial position Track pitch inner circumference side 4.8mm ~ 6.6mm 300nm
Middle 6.6mm-8.4mm 400nm
Outer peripheral side: 8.4 mm to 10.2 mm 500 nm.

  The width of the nonmagnetic part (guard band) was 100 nm in any region. Therefore, this magnetic disk has a structure as shown in FIG. 4, and the area ratio of the magnetic layer pattern 52 / nonmagnetic portion on the outer peripheral side is larger than that on the inner peripheral side.

  A magnetic disk was manufactured in the same manner as in Example 1 by using the disk substrate imprinted on the 1000th sheet. A magnetic recording apparatus as shown in FIG. 6 was manufactured using the manufactured magnetic disk, and a magnetic head flying test was performed by rotating the magnetic disk. As a result, flying height data as shown in FIG. 11 was obtained. As shown in this figure, the flying height increased toward the outer peripheral side of the magnetic disk, but the magnetic signal could be satisfactorily reproduced on the entire disk surface.

  For comparison, a magnetic disk having a track pitch of 300 nm and a non-magnetic portion (guard band) width of 100 nm in all data regions having a radial position of 4.8 mm to 10.2 mm was manufactured. The magnetic signal was reproduced by flying the head. As a result, a reproduction error occurred at the outer periphery, and reproduction was impossible.

  In the above, the magnetic disk in which the magnetic layer pattern is separated by the guard band including the grooves has been described. However, the magnetic disk according to the embodiment of the present invention has a nonmagnetic material embedded in the groove portion between the magnetic layer patterns. Thereafter, the surface may be flattened through a processing process such as polishing and etching.

  FIG. 12 shows a cross-sectional view of such a magnetic disk. In FIG. 12, an underlayer 102, a magnetic recording layer 103, and a protective layer 104 are formed on a disk substrate 101, and a lubricating layer 105 is applied to the surface. The magnetic recording layer 103 includes a magnetic layer pattern 111 and a non-magnetic material 112 filling the space, and the surface is flattened. The protective layer 104 formed thereon has a substantially uneven surface according to cross-sectional observation with an electron microscope and AFM measurement. However, it was found that when the head slider was levitated, changes and fluctuations in the flying height were observed such that the surface of the magnetic disk had irregularities. When the reason was examined in detail, it was found that the thickness of the lubricating layer 105 was different between the magnetic part and the non-magnetic part. The reason is not clear, but it is recalled that the following phenomenon is occurring. As shown in FIG. 12, on the magnetic part and the non-magnetic part in the magnetic recording layer 103, the film quality is microscopically different depending on the interface where the growth of the DLC protective layer 104 is started. As a result, the atomic structure of the surface of the DLC protective layer 104 is different. In FIG. 12, the surface of the DLC protective layer 104 grown on the magnetic material portion is indicated by a thick line. For this reason, the thickness of the lubricant is also different on the DLC protective layer 104 having a different surface atomic structure. It is generally known to those skilled in the art that the thickness of the adhering lubricant varies depending on the difference in the film quality of DLC based on the difference in the film formation method. Since this phenomenon occurs microscopically, the thickness of the lubricating layer becomes different as shown in FIG. Since the head slider feels the surface of the lubricating layer 105 as an effective bottom surface that serves as a reference for flying, it is considered that this difference in thickness leads to differences and fluctuations in the flying height.

  Hereinafter, materials used for each layer of the magnetic disk according to the embodiment of the present invention and a laminated structure of each layer will be described.

<Magnetic disk substrate>
As the magnetic disk substrate, for example, a glass substrate, an Al-based alloy substrate, a ceramic substrate, a carbon substrate, a Si single crystal substrate having an oxidized surface, and a substrate in which a NiP layer is formed on the surface of these substrates can be used. Amorphous glass or crystallized glass can be used for the glass substrate. Examples of the amorphous glass include soda lime glass and aluminosilicate glass. Examples of crystallized glass include lithium-based crystallized glass. As the ceramic substrate, a sintered body mainly composed of aluminum oxide, aluminum nitride, silicon nitride or the like, or a fiber reinforced one of these sintered bodies can be used. To form the NiP layer on the surface of the substrate, plating or sputtering is used.

<Soft magnetic underlayer>
When producing a perpendicular magnetic recording medium, a so-called perpendicular double-layer medium having a perpendicular magnetic recording layer on a soft magnetic underlayer (SUL) is used. The soft magnetic underlayer of the perpendicular double-layer medium is provided in order to pass the recording magnetic field from the recording magnetic pole and to return the recording magnetic field to the return yoke disposed in the vicinity of the recording magnetic pole. That is, the soft magnetic underlayer plays a part of the function of the recording head and plays a role of improving the recording efficiency by applying a steep vertical magnetic field to the recording layer.

  For the soft magnetic underlayer, a high magnetic permeability material containing at least one of Fe, Ni, and Co is used. Such materials include FeCo alloys such as FeCo and FeCoV, FeNi alloys such as FeNi, FeNiMo, FeNiCr and FeNiSi, FeAl alloys and FeSi alloys such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, FeAlO, and FeTa alloys such as Examples thereof include FeZr alloys such as FeTa, FeTaC, and FeTaN, such as FeZrN.

  For the soft magnetic underlayer, a material having a fine crystal structure such as FeAlO, FeMgO, FeTaN, FeZrN or the like containing Fe at 60 at% or more or a granular structure in which fine crystal particles are dispersed in a matrix can be used.

  As another material of the soft magnetic underlayer, a Co alloy containing Co and at least one of Zr, Hf, Nb, Ta, Ti, and Y can be used. Co is preferably contained at 80 at% or more. When such a Co alloy is formed by sputtering, an amorphous layer is easily formed. Amorphous soft magnetic materials do not have magnetocrystalline anisotropy, crystal defects, and grain boundaries, and thus exhibit very excellent soft magnetism. Further, the use of an amorphous soft magnetic material can reduce the noise of the medium. Suitable examples of the amorphous soft magnetic material include CoZr, CoZrNb, and CoZrTa-based alloys.

  An underlayer may be further provided under the soft magnetic underlayer in order to improve the crystallinity of the soft magnetic underlayer or the adhesion to the substrate. As the underlayer material, Ti, Ta, W, Cr, Pt, alloys containing these, or oxides or nitrides thereof can be used.

  An intermediate layer made of a non-magnetic material may be provided between the soft magnetic underlayer and the perpendicular magnetic recording layer. The role of the intermediate layer is to block the exchange coupling interaction between the soft magnetic underlayer and the recording layer and to control the crystallinity of the recording layer. As the intermediate layer material, Ru, Pt, Pd, W, Ti, Ta, Cr, Si, an alloy containing these, or an oxide or nitride thereof can be used.

  In order to prevent spike noise, the soft magnetic underlayer may be divided into a plurality of layers and antiferromagnetically coupled by sandwiching Ru having a thickness of 0.5 to 1.5 nm. Alternatively, the soft magnetic layer and a pinning layer made of a hard magnetic film having in-plane anisotropy such as CoCrPt, SmCo, or FePt or an antiferromagnetic material such as IrMn or PtMn may be exchange-coupled. In this case, in order to control the exchange coupling force, a magnetic layer such as Co or a nonmagnetic layer such as Pt may be laminated on the upper and lower sides of the Ru layer.

<Perpendicular magnetic recording layer>
For the perpendicular magnetic recording layer, for example, a material containing Co as a main component, containing at least Pt, optionally containing Cr, and further containing an oxide (for example, silicon oxide or titanium oxide) is used. In the perpendicular magnetic recording layer, the magnetic crystal grains preferably have a columnar structure. In the perpendicular magnetic recording layer having such a structure, the orientation and crystallinity of the magnetic crystal grains are good, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. In order to obtain the above structure, the amount of oxide is important. The content of the oxide is preferably 3 mol% or more and 12 mol% or less, and more preferably 5 mol% or more and 10 mol% or less with respect to the total amount of Co, Pt, and Cr. When the content of the oxide in the perpendicular magnetic recording layer is in the above range, the oxide is precipitated around the magnetic particles, and the magnetic particles can be isolated and refined. When the content of the oxide exceeds the above range, the oxide remains in the magnetic particles, the orientation and crystallinity of the magnetic particles are impaired, and further, oxides are deposited above and below the magnetic particles. As a result, the magnetic particles However, a columnar structure penetrating the perpendicular magnetic recording layer vertically is not formed. On the other hand, when the oxide content is less than the above range, isolation and miniaturization of the magnetic particles are insufficient, resulting in an increase in noise during recording and reproduction, and a signal / noise ratio suitable for high density recording ( (S / N ratio) cannot be obtained.

  The Pt content in the perpendicular magnetic recording layer is preferably 10 at% or more and 25 at% or less. When the Pt content is in the above range, the uniaxial magnetic anisotropy constant Ku necessary for the perpendicular magnetic recording layer can be obtained, and the crystallinity and orientation of the magnetic particles are improved, which is suitable for high density recording as a result. Thermal fluctuation characteristics and recording / reproduction characteristics can be obtained. When the Pt content exceeds the above range, a layer having an fcc structure is formed in the magnetic particles, and the crystallinity and orientation may be impaired. On the other hand, when the Pt content is less than the above range, Ku suitable for high density recording, and hence thermal fluctuation characteristics, cannot be obtained.

  The Cr content in the perpendicular magnetic recording layer is preferably 0 at% or more and 16 at% or less, and more preferably 10 at% or more and 14 at% or less. When the Cr content is in the above range, high magnetization can be maintained without lowering the uniaxial magnetic anisotropy constant Ku of the magnetic particles, and as a result, recording / reproducing characteristics suitable for high-density recording and sufficient thermal fluctuation characteristics can be obtained. . When the Cr content exceeds the above range, the Ku of the magnetic particles is reduced, so that the thermal fluctuation characteristics are deteriorated, and the crystallinity and orientation of the magnetic particles are deteriorated. As a result, the recording / reproducing characteristics are deteriorated.

  The perpendicular magnetic recording layer contains one or more additive elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Pt, Cr, and oxide. You may go out. By including these additive elements, it is possible to promote miniaturization of magnetic particles or improve crystallinity and orientation, and to obtain recording / reproducing characteristics and thermal fluctuation characteristics suitable for higher density recording. it can. The total content of these additive elements is preferably 8 at% or less. If it exceeds 8 at%, phases other than the hcp phase are formed in the magnetic particles, so that the crystallinity and orientation of the magnetic particles are disturbed, resulting in recording / reproduction characteristics and thermal fluctuation characteristics suitable for high-density recording. It becomes impossible.

  Other materials for the perpendicular magnetic recording layer include CoPt alloys, CoCr alloys, CoPtCr alloys, CoPtO, CoPtCrO, CoPtSi, and CoPtCrSi. For the perpendicular magnetic recording layer, a multilayer film of Co and an alloy mainly composed of at least one selected from the group consisting of Pt, Pd, Rh, and Ru can be used. In addition, a multilayer film such as CoCr / PtCr, CoB / PdB, or CoO / RhO to which Cr, B, or O is added can be used for each layer of these multilayer films.

  The thickness of the perpendicular magnetic recording layer is preferably 5 to 60 nm, and more preferably 10 to 40 nm. A perpendicular magnetic recording layer having a thickness in this range is suitable for high recording density. If the thickness of the perpendicular magnetic recording layer is less than 5 nm, the reproduction output tends to be too low and the noise component tends to be higher. On the other hand, if the thickness of the perpendicular magnetic recording layer exceeds 40 nm, the reproduction output tends to be too high and the waveform tends to be distorted. The coercive force of the perpendicular magnetic recording layer is preferably 237000 A / m (3000 Oe) or more. When the coercive force is less than 237000 A / m (3000 Oe), the thermal fluctuation resistance tends to be inferior. The perpendicular squareness ratio of the perpendicular magnetic recording layer is preferably 0.8 or more. When the vertical squareness ratio is less than 0.8, the thermal fluctuation resistance tends to be inferior.

<Protective layer>
The protective layer functions to prevent corrosion of the perpendicular magnetic recording layer and to prevent damage to the medium surface when the magnetic head comes into contact with the medium. Examples of the material for the protective layer include materials containing C, SiO ₂ , and ZrO ₂ . The thickness of the protective layer is preferably 1 to 10 nm. When the thickness of the protective layer is in the above range, the distance between the head and the medium can be reduced, which is suitable for high density recording.

<Lubrication layer>
As the lubricant, for example, perfluoropolyether, fluorinated alcohol, fluorinated carboxylic acid and the like can be used.

1 is a plan view schematically showing a magnetic disk (discrete track medium) according to an embodiment of the present invention. 1 is a plan view showing an example of a magnetic layer pattern formed on a surface of a magnetic disk according to an embodiment of the present invention. Sectional drawing which shows an example of the magnetic disc from which the area ratio of a magnetic layer pattern and a nonmagnetic part differs according to radial position based on embodiment of this invention. Sectional drawing which shows the other example of the magnetic disc from which the area ratio of a magnetic layer pattern and a nonmagnetic part differs according to radial position based on embodiment of this invention. Sectional drawing which shows the further another example of the magnetic disk which differs in the area ratio of a magnetic layer pattern and a nonmagnetic part based on radial position based on embodiment of this invention. 1 is a perspective view showing a magnetic recording apparatus according to an embodiment of the present invention. Sectional drawing which shows the manufacturing method of the stamper used in the Example of this invention. Sectional drawing which shows the manufacturing method of the magnetic disc in the Example of this invention. FIG. 3 is a diagram showing flying data of the magnetic head with respect to the magnetic disk of Example 1. The figure which shows the flying data of the magnetic head with respect to the magnetic disk of a reference example. FIG. 6 is a diagram showing flying data of a magnetic head with respect to a magnetic disk of Example 2. Sectional drawing of the magnetic disc which concerns on other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 2 ... Servo area, 3 ... Data area, 21 ... Preamble part, 22 ... Address part, 23 ... Burst part, 31 ... Recording track, 32 ... Guard band, 41 ... Si wafer, 42 ... Resist, 45 DESCRIPTION OF SYMBOLS: Resist master, 46 ... Conductive film, 47 ... Electroformed film, 48 ... Stamper, 51 ... Disk substrate, 52 ... Magnetic recording layer, 53 ... Carbon protective film, 55 ... Resist, 70 ... Housing, 71 ... Magnetic disk, 72 ... Spindle motor, 73 ... Pivot, 74 ... Actuator arm, 75 ... Suspension, 76 ... Head slider, 77 ... Voice coil motor (VCM), 101 ... Disk substrate, 102 ... Underlayer, 103 ... Magnetic recording layer, 104 ... Protective layer, 105 ... lubricating layer, 111 ... magnetic layer pattern, 112 ... nonmagnetic material.

Claims (2)

A data area including a magnetic layer pattern forming a recording track, a servo area including a magnetic layer pattern used as a servo signal, and a nonmagnetic portion for separating the magnetic layer pattern formed on the disk substrate. The width of the nonmagnetic portion in the data area is constant regardless of the radial position, and the pitch of the recording track in the data area is smaller on the outer peripheral side than on the inner peripheral side, and the data A magnetic disk, wherein an area ratio between the pattern of the magnetic layer and the nonmagnetic portion in the region varies depending on a radial position. A magnetic disk device comprising the magnetic disk according to claim 1 and a floating magnetic head.

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