JP2006048769A - Magnetic recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recorder having a discrete track medium wherein a magnetic layer pattern formed in a servo area shows excellent durability to stress accompanied by the flotation of a head slider. <P>SOLUTION: This magnetic recorder has a magnetic recording medium, a spindle for rotating the magnetic recording medium, the head slider of a flotation type and an actuator for moving the head slider on the magnetic recording medium. The magnetic recording medium has a data area including a pattern of a magnetic layer constituting a recording track, a servo area including a pattern of the magnetic layer used as a servo signal and a non-magnetic part for filling a part between patterns of the magnetic layer, wherein the servo area is arranged circularly on the magnetic recording medium and the curvature of a circular arc is not longer than 20 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic recording apparatus including a magnetic recording medium having discrete tracks.

  In recent years, in order to cope with further increase in the density of magnetic recording media, discrete track media in which adjacent recording tracks are separated by a guard band made up of non-magnetic portions to reduce magnetic interference between adjacent tracks have attracted attention. Collecting. In order to put such a discrete track medium into practical use, it is required to satisfy various requirements.

Conventionally, a magnetic recording medium in which the arrangement of servo areas has been devised in order to suppress fluctuations in the flying height of the head slider has been proposed (Patent Document 1). However, in this proposal, the durability of the magnetic recording medium incorporated in the magnetic recording apparatus is not studied.
JP-A-10-261276

  When reading and writing information with respect to a magnetic recording medium having a discrete track (discrete track medium) using a flying head slider, the head slider is flying with pressure generated by a pad on the surface facing the medium. At the same time, the medium is subjected to a stress corresponding to the pressure. The servo layer of the discrete track medium is concentrated with a magnetic layer pattern that is processed to be smaller than the data region, and the stress accompanying the flying of the head slider tends to induce a large distortion in the magnetic layer pattern. This strain is instantaneously induced on the disk substrate side and propagates as an elastic wave to the entire disk substrate. This elastic wave is more strongly propagated in the radial direction due to the symmetry of the disk substrate. For this reason, if there is a servo region in the traveling direction of the elastic wave, further distortion is induced in the magnetic layer pattern. It has been found that when this phenomenon is repeated many times, the magnetic layer pattern undergoes elastic fatigue and pattern peeling occurs.

  It is an object of the present invention to provide a magnetic recording apparatus having a discrete track medium in which a magnetic layer pattern formed in a servo area exhibits good durability against stress associated with flying of a head slider.

  A magnetic recording apparatus according to an aspect of the present invention includes a magnetic recording medium, a spindle that rotates the magnetic recording medium, a floating head slider, and an actuator that moves the head slider on the magnetic recording medium. In the magnetic recording apparatus, the magnetic recording medium includes a data region including a magnetic layer pattern forming a recording track, a servo region including a magnetic layer pattern used as a servo signal, and a non-filling space between the magnetic layer patterns. The servo area is arranged in an arc shape on the magnetic recording medium, and the radius of curvature of the arc is 20 mm or less.

  According to the present invention, the servo area is arranged in an arc shape on the magnetic recording medium and the curvature of the arc is set to 20 mm or less, and the servo area in the propagation direction of the elastic wave induced in the disk substrate by the stress accompanying the flying of the head slider. Therefore, damage due to elastic fatigue (peeling of the magnetic layer pattern) can be prevented.

Example 1
A magnetic recording apparatus using a discrete track medium according to an embodiment of the present invention will be described with reference to FIG. The magnetic recording apparatus includes a housing 70, 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 shielded 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 recording surface of the magnetic disk 71. The actuator arm 74 is attached to the pivot 73. The other end of the actuator arm 74 is provided with a voice coil motor (VCM) 77 as an actuator. 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. 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.

  FIG. 2 shows a cross-sectional view of the magnetic disk according to the present embodiment. The magnetic disk shown in FIG. 2 is obtained by depositing a soft magnetic underlayer (SUL) 12, a recording layer 13, and a protective layer 14 on a disk substrate 11 and coating a lubricating layer 15 on the protective layer 14. The magnetic disk according to this embodiment is characterized in that the pattern of the magnetic body 16 is separated by the non-magnetic 17 that fills the pattern. Thus, by dividing the magnetic layer with a non-magnetic material, for example, in the servo region, a signal can be obtained depending on the presence or absence of the magnetic layer.

  The heights of the magnetic part 16 and the nonmagnetic part 17 were made to be approximately the same, and when the unevenness difference was measured by AFM from above the protective layer 14, it was 0.3 nm or less.

  The materials used for this magnetic disk and the laminated structure of each layer can be the same as those used for ordinary perpendicular magnetic recording media. Hereinafter, materials used for each layer of the magnetic disk and a laminated structure of each layer will be described.

<Board>
As the substrate 11, for example, a glass substrate, an Al-based alloy substrate, a ceramic substrate, a carbon substrate, an 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>
The magnetic recording medium shown in FIG. 2 is a so-called perpendicular double-layer medium having a perpendicular magnetic recording layer on a soft magnetic underlayer (SUL). The soft magnetic underlayer of the perpendicular double-layer medium is provided 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, by using an amorphous soft magnetic material, it is possible to 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, if 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 / reproduction 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 poor.

<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.

  FIG. 3 is a plan view schematically showing the surface of the recording layer 13. As shown in FIG. 3, servo areas 22 and data areas 23 are alternately formed in the track area 21 formed along the circumferential direction. In the data area 23, the magnetic layer is left as much as the track width, and the space between the tracks (guard band) is filled with a nonmagnetic portion. In FIG. 3, for easy understanding, a gap is drawn between the tracks, and the track region 21 is clearly indicated by a dotted line. User data is recorded in the data area 23 as magnetic information. Further, the data regions 23 and the nonmagnetic portions (guard bands) 24 are alternately formed along the radial direction. Although not shown in FIG. 3, a magnetic layer pattern used as a servo signal is formed in the servo region 22. The guard band may not be in the servo area.

  FIG. 4 shows the pattern of the perpendicular magnetic recording layer in the servo area and the data area in more detail. As shown in FIG. 4, the servo area 22 includes a preamble, an address area 25, an ABCD burst area 26, a mirror portion, and the like. These servo signals are formed by the magnetic body portion 16 and the non-magnetic portion 17, and the magnetic head reads the servo signal from a change in magnetic flux caused by the presence or absence of the magnetic body portion 16.

The magnetic disk schematically shown in FIGS. 2 to 4 can be manufactured as follows.
<Stamper production>
First, a master plate from which the pattern was based was prepared.
A photosensitive resin was applied on the Si substrate, an electron beam was applied to the photosensitive resin layer to form a latent image, and the latent image was developed to form a concavo-convex pattern. The concavo-convex pattern was formed using an exposure apparatus having a signal source for irradiating the photosensitive resin on the substrate with an electron beam at a predetermined timing and a stage for moving the substrate with high precision in synchronization with the signal source. . A Ni conductive film was formed on the prepared resist master by an ordinary sputtering method. Next, a nickel electroformed film was formed on the conductive film by electroforming. The liquid used for electroforming was Showa Chemical Co., Ltd. high concentration nickel sulfamate plating solution (NS-160). The thickness of this electroformed film was 300 μm. Thereafter, the electroformed film is peeled off from the resist master, thereby obtaining a stamper provided with the conductive film, the electroformed film and the resist residue. Next, the resist residue is removed by an oxygen plasma ashing method.

  The father stamper thus obtained can be used as an imprint stamper. The above-mentioned electroforming process was repeated on this father stamper, and the stamper was mass-replicated. First, an oxide film was formed on the surface of the father stamper by passivation using an oxygen plasma ashing method similar to the step of removing the resist residue. Thereafter, a nickel electroformed film was formed by the same method as described above by electroforming. Thereafter, the electroformed film was peeled off from the father stamper to obtain a mother stamper which is an inverted type of the father stamper. Ten or more mother stampers having the same shape were obtained by repeating the process of obtaining the mother stamper from the father stamper. Thereafter, in the same manner as the procedure for obtaining the mother stamper from the father stamper, an oxide film was passivated on the mother stamper surface, and an electroformed film was formed and peeled to obtain a sun stamper having the same uneven shape as the father stamper.

<Imprint>
After ultrasonically cleaning the sun stamper with acetone for 5 minutes, fluoroalkylsilane [CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OMe) which is a fluorinated release resin containing chlorinated fluororesin containing silane coupling agent ₃ ] was immersed in a solution diluted to 2% with ethanol for 30 minutes or more, and the solution was blown off with a blower, followed by annealing at 120 ° C. for 1 hour in a nitrogen atmosphere. The above magnetic recording medium is coated with a resist (Rohm & Haas Electronic Materials Co., Ltd., trade name S1818 diluted 5 times with propyleneglycol monomethyl ether acetate (PGMEA), or S1801) with a spin coater. The pattern was transferred to the resist by pressing the formed stamper at 450 bar for 60 seconds. Thereafter, the stamper was peeled off, and the uneven surface shape was cured by UV irradiation for 5 minutes, and then heated at 160 ° C. for 30 minutes.

<Medium etching>
In order to remove the resist residue in the recesses on the magnetic recording medium, RIE with oxygen gas was performed. Subsequently, the magnetic recording medium is etched by Ar ion milling. In order to eliminate damage to the ferromagnetic recording layer and suppress reattachment, etching was performed while changing the ion incident angle between 30 ° and 70 °. After etching the magnetic material, oxygen RIE was used to remove the etching mask. After processing the magnetic material, a carbon protective film was formed as a protective film. A lubricant was applied to the produced medium by a dip method.

  The magnetic disk produced by the above process has large irregularities with a relatively high level difference on the surface. Note that a medium having unevenness on the surface can also be produced by increasing the amount of etch back.

  For example, the following steps are used to obtain a magnetic recording medium having a substantially flat surface as shown in FIG. The stamper manufacturing process is the same as described above. In the imprint process, SOG (Spin On Glass) was applied to the magnetic recording medium with a spin coater. Depending on the chemical structure of the siloxane, SOG uses silica glass, alkylsiloxane polymer, alkylsilsesquioxane polymer (MSQ), hydrogenated silsesquioxane polymer (HSQ), hydrogenated alkylsiloxane polymer (HOSP). ) Etc. Here, T-7 manufactured by Tokyo Ohka Kogyo Co., Ltd. and FOX manufactured by Dow Corning Co., Ltd., diluted 5-fold with methyl isobutyl ketone (MIBK) were used. After applying SOG, it was placed in an oven, pre-baked at 100 ° C. for 20 minutes, the solvent in SOG was blown off, and the stamper was pressed at 450 bar for 60 seconds to transfer the pattern onto the resist.

Next, in the etching process, residue removal of the SOG film was performed using an ICP (Inductively Coupled Plasma) etching apparatus. SF ₆ was used as an etching gas. The milling process of the magnetic recording medium is the same as described above.

After milling, SOG similar to the SOG used for the resist was applied with a spin coater and embedded. Thereafter, etching back was performed until the magnetic film appeared again by milling. For filling, a process of forming a film of SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ or the like by a normal sputtering method and then etching back by milling can be used. Any material that can be sputtered can be used as the material of the dielectric portion.

  In this embodiment, the servo area 22 is formed in an arc shape on the medium 31 as shown in FIG. 5 by shifting the timing at which the servo area starts to be formed for each disk radius during pattern exposure. Reference numeral 32 denotes a disk radial direction, and the servo area 22 has a radius of curvature 34 on the scale of the entire disk surface, with the center of the arc being 33. There are as many arcs as there are servo areas per revolution, but only one is shown in the figure for simplicity.

  By changing the timing deviation of the servo area during pattern exposure to various values, 10 magnetic disks each having a curvature radius of 15, 20, 25, and 30 mm are produced, and 10 magnetic recording devices are produced. did. This disk was put into an accelerated environment test machine set to repeat the temperature between 10 ° C. and 40 ° C. every 2 hours, and rotated at 4500 rpm, and an accelerated deterioration experiment in which random access was always performed was conducted for 24 hours. . When a servo operation did not occur or a head crash occurred, it was counted as an error, and the error occurrence rate of 10 drives was examined under each curvature radius condition. The result is shown in FIG.

  As is apparent from FIG. 6, the smaller the radius of curvature, the lower the error rate. In the case of 20 mm, only one unit caused an error. Considering the acceleration environment, it can be judged that the drive is acceptable in the normal use environment. Accordingly, it has been found that when the radius of curvature is 20 mm or less, a magnetic recording apparatus that is less prone to error even in an acceleration environment can be obtained. In order to obtain a drive that is more environmentally friendly, the radius of curvature is preferably 15 mm or less.

  The reason why the above results were obtained is not well understood because no similar examples have been reported. However, it is assumed that the following mechanism is the cause.

The head slider flies by generating pressure due to airflow using a pattern consisting of minute pads formed on the surface facing the medium. At the same time, a stress corresponding to the pressure is generated in a minute area on the medium side. It means giving. In the case of the discrete track medium as in this embodiment, the servo area is concentrated with a magnetic layer pattern that is processed to be smaller than the data area, and this stress causes a relatively large distortion with respect to the small magnetic layer pattern. Easy to induce. The stress also acts on the substrate side and induces strain though it is minute. The distortion of the magnetic layer pattern and the substrate is instantaneous only during the passage of the slider, but because it is instantaneous, it propagates to the entire disk as a pulsed elastic wave. This elastic wave is propagated more strongly in the radial direction due to the symmetry of the substrate, and if there is a servo region in the traveling direction, distortion is induced one after another in the minute magnetic layer pattern in the servo region as the elastic wave passes. To go. Accordingly, even if the head does not pass through, distortion is induced in the servo area, and this is repeated many times, such as 10 ⁴ to 10 ⁶ times, causing elastic fatigue, and the magnetic layer in the servo area. Pattern peeling occurs. If the peeled magnetic layer pattern becomes dust, it causes a crash. Further, peeling of the magnetic layer pattern means a lack of servo information, which causes a tracking error. In particular, in an accelerated test environment, the effect of expansion and contraction of the magnetic layer due to temperature change is added, and peeling is more likely to occur.

  In order to prevent this, it is only necessary that the servo regions 22 are not aligned in the propagation direction of the elastic wave. A shape in which the elastic wave propagating linearly in the radial direction does not follow is a curve. If it is a curve, the elastic wave passes at least once, but the point may be regarded as a point, and unless the head passes, no distortion is induced, so that the servo area is not damaged widely. When an arc having a certain curvature is used as an example of a curve, the smaller the curvature, the smaller the region through which the elastic wave passes, and the damage is further reduced. In the case of the magnetic disk of this embodiment mainly composed of glass, as can be seen from FIG. 5, the radius of curvature of the servo region may be 20 mm or less, and more preferably 15 mm or less. However, if the radius of curvature is less than 4 mm, the servo region cannot be formed substantially, so the radius of curvature needs to be 4 mm or more.

(Example 2)
From the knowledge of Example 1, it is assumed that the same phenomenon occurs even when the unevenness on the disk surface is larger than 0.3 nm. Therefore, the process of embedding and flattening was changed to produce a magnetic disk in which the nonmagnetic material 17 was thinner than the pattern of the magnetic material 16 as shown in FIG. In the figure, t is the unevenness difference between the magnetic layer and the nonmagnetic part. As shown in the figure, this unevenness difference can be measured from above the protective film 14 by AFM or the like. In general, the disk surface has a roughness of about 0.3 to 1 nm. This roughness is generally described by the average roughness Ra. The unevenness difference may be smaller than Ra. An example is shown in FIG. FIG. 8 is drawn with the vertical axis emphasized, but the unevenness difference is indicated by the distance shown in the figure (0.4 nm in the figure).

  Magnetic disks having unevenness differences of 0.4 nm, 1 nm, 2 nm, 5 nm, 10 nm, and 20 nm were produced, and a medium having a curvature radius of 20 mm shown in FIG. 5 was produced. Ten magnetic recording devices were produced using 10 magnetic disks each. Thereafter, an accelerated environment test was performed using the same apparatus as in Example 1. The result is shown in FIG. Although there were variations due to the test of 10 units, it was found that the same result was obtained even with a medium having a difference in roughness of 0.4 nm or more. This can be understood from the fact that the effect of the present invention is not related in principle to the unevenness of the magnetic disk. However, the error rate increased slightly when the unevenness difference was 20 nm. This is presumably because tracking errors are likely to occur due to fluctuations in the flying height due to the difference in the ratio between the magnetic layer and the nonmagnetic portion. In order to obtain a magnetic recording apparatus that can be used even in a harsh environment, the unevenness difference is preferably 20 nm or less, and more preferably 10 nm or less.

(Example 3)
The same apparatus as in Example 1 was prototyped. However, the manufacturing method of the magnetic disk was changed. A photoresist was spin coated on the substrate. A stamper having a pattern having a servo area and a data area as shown in FIG. 3 was prepared, and the pattern was transferred onto the substrate by pressing from above the photoresist. Thereafter, the resist pressing residue was removed by an oxygen RIE process to expose the glass substrate surface. Thereafter, the glass substrate was etched by an RIE process using CF ₄ gas. The etching depth is 50 nm. On top of this, a continuous film was produced in the same process as that for producing a normal perpendicular magnetic recording medium. Since the substrate has irregularities, irregularities exist on the surface of the magnetic disk. A sectional view of this magnetic disk is shown in FIG. In this case, the nonmagnetic portion in the recording layer 13 becomes a part of the protective layer 14.

  In addition, a magnetic disk having a nonmagnetic portion 17 formed by embedding and flattening a nonmagnetic material before laminating the protective layer 14 was also produced. A sectional view of this magnetic disk is shown in FIG.

  For these two magnetic disks, the same experiment as in Example 1 was performed. As a result, the same results as in FIGS. 6 and 9 were obtained. That is, it was found that even a magnetic recording apparatus having a magnetic disk manufactured using a substrate having irregularities can prevent tracking errors. This can be understood from the fact that the effect of the present invention is not related in principle to the unevenness of the medium.

  When producing a medium by the method of this example, it is necessary to employ a magnetic layer deposition process that prevents the magnetic layer from adhering to the wall surface against the irregularities of the glass substrate. Although it is difficult, there is an advantage that the processing process of the magnetic layer is not required, and depending on the specifications of the magnetic recording apparatus, it can be manufactured at a lower cost.

1 is a perspective view of a magnetic recording apparatus according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view of a magnetic disk used in the magnetic recording apparatus according to the first embodiment. FIG. 3 is a plan view schematically showing a recording layer surface of the magnetic disk of FIG. 2. FIG. 4 is a plan view showing a servo area and a data area of the magnetic disk of FIG. 3 in more detail. FIG. 3 is a diagram schematically showing a positional relationship of servo areas on the surface of the magnetic disk according to the first embodiment. FIG. 3 is a diagram showing a relationship between a radius of curvature of a servo area and an error occurrence rate for the magnetic disk according to the first embodiment. FIG. 6 is a cross-sectional view showing a part of a magnetic disk used in the magnetic recording apparatus in Example 2. The figure which shows typically the relationship between the surface roughness of a magnetic disc, and uneven | corrugated difference t. FIG. 4 is a diagram showing the relationship between the unevenness difference t and the tracking error occurrence rate for the magnetic disk according to the first embodiment. FIG. 6 is a cross-sectional view of an example of a magnetic recording medium used in the magnetic recording apparatus of Example 3. FIG. 6 is a cross-sectional view of another example of a magnetic recording medium used in the magnetic recording apparatus of Example 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Disk substrate, 12 ... Underlayer, 13 ... Recording layer, 14 ... Protective layer, 15 ... Lubrication layer, 16 ... Magnetic body part, 17 ... Nonmagnetic part, 21 ... Recording track area, 22 ... Servo area, 23 ... Data area 25 ... Address area 26 ... Burst area 31 ... Magnetic disk 32 ... Radial direction 33 ... Arc center 34 ... Radius of curvature 70 ... Housing 71 ... Magnetic disk 72 ... Spindle motor 73 Pivot 74 Actuator arm 75 Suspension 76 Head slider 77 Voice coil motor (VCM)

Claims (3)

  A magnetic recording apparatus comprising: a magnetic recording medium; a spindle for rotating the magnetic recording medium; a floating head slider; and an actuator for moving the head slider on the magnetic recording medium. The magnetic recording medium is a recording track. A data region including a magnetic layer pattern, a servo region including a magnetic layer pattern used as a servo signal, and a nonmagnetic portion for separating the magnetic layer pattern, wherein the servo region is the magnetic region. A magnetic recording apparatus, wherein the magnetic recording apparatus is arranged in an arc shape on a recording medium, and the radius of curvature of the arc is 20 mm or less.   2. The magnetic recording apparatus according to claim 1, wherein a difference in height between the pattern of the magnetic layer and the nonmagnetic portion is 0.4 nm or more.   The magnetic recording apparatus according to claim 1, wherein a substrate of the magnetic recording medium has irregularities.

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