JP2004086936A - Magnetic recording medium, its manufacturing method and magnetic recording and reproducing device - Google Patents

Magnetic recording medium, its manufacturing method and magnetic recording and reproducing device Download PDF

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Publication number
JP2004086936A
JP2004086936A JP2002242518A JP2002242518A JP2004086936A JP 2004086936 A JP2004086936 A JP 2004086936A JP 2002242518 A JP2002242518 A JP 2002242518A JP 2002242518 A JP2002242518 A JP 2002242518A JP 2004086936 A JP2004086936 A JP 2004086936A
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Prior art keywords
alloy
magnetic
magnetic recording
layer
recording medium
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JP2002242518A
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JP2004086936A5 (en
Inventor
Hiroshi Osawa
大澤 弘
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Showa Denko Kk
昭和電工株式会社
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Priority to JP2002242518A priority Critical patent/JP2004086936A/en
Priority claimed from US10/645,625 external-priority patent/US7006328B2/en
Publication of JP2004086936A publication Critical patent/JP2004086936A/en
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Abstract

A magnetic recording medium having excellent electromagnetic conversion characteristics and suitable for high recording density is obtained.
A magnetic recording medium having at least an orientation adjusting layer, a non-magnetic underlayer, a magnetic layer, and a protective film in this order on a glass substrate having a streak on its surface, wherein the orientation adjusting layer is made of Co, Ni and It is formed to include any one or more selected from Fe and any one or more selected from W, Mo, Ta, and Nb. Further, the orientation adjusting layer may be made of a Co-W alloy, a Co-Mo alloy, a Co-Ta alloy, a Co-Nb alloy, a Ni-Ta alloy, a Ni-Nb alloy, a Fe-W alloy, a Fe-W alloy. -Formed to include at least one alloy selected from a Mo-based alloy and an Fe-Nb-based alloy.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording medium used for a hard disk device and the like, a method for manufacturing a magnetic recording medium, and a magnetic recording / reproducing apparatus.
[0002]
[Prior art]
Hard disk drives (HDDs), which are one type of magnetic recording / reproducing devices, are currently increasing their recording density at an annual rate of 60%, and it is said that the trend will continue in the future. Development of a magnetic recording head suitable for a high recording density and development of a magnetic recording medium have been advanced.
[0003]
A magnetic recording medium used in a hard disk drive is required to have a high recording density, and accordingly, an improvement in coercive force and a reduction in medium noise are required.
[0004]
As a magnetic recording medium used in a hard disk drive, a structure in which a metal film is laminated on a substrate for a magnetic recording medium by a sputtering method is mainly used. Aluminum substrates and glass substrates are widely used as substrates used for magnetic recording media. The aluminum substrate is obtained by forming a Ni-P-based alloy film to a thickness of about 10 µm on a mirror-polished Al-Mg alloy substrate by electroless plating, and further mirror-finish the surface thereof. There are two types of glass substrates, amorphous glass and crystallized glass. Both glass substrates used are mirror-finished.
[0005]
In a magnetic recording medium for a hard disk drive generally used at present, a non-magnetic underlayer (Ni-Al alloy, Cr, Cr-based alloy, etc.) and a non-magnetic intermediate layer (Co -Cr, Co-Cr-Ta-based alloy, etc.), a magnetic layer (Co-Cr-Pt-Ta, Co-Cr-Pt-B-based alloy, etc.), and a protective film (carbon, etc.) are sequentially formed. And a lubricating film made of a liquid lubricant is formed thereon.
[0006]
With the increase in recording density of magnetic disk devices and the like, a magnetic recording medium having magnetic anisotropy in the circumferential direction and having good electromagnetic conversion characteristics is required. For this reason, at present, a magnetic recording medium using a substrate obtained by plating NiP on an aluminum alloy (also referred to as “aluminum substrate”) is mechanically provided with grooves in the surface of the NiP in the circumferential direction (referred to as “mechanical texture processing”). ) To provide magnetic anisotropy in the circumferential direction.
[0007]
On the other hand, a non-magnetic substrate, for example, a glass substrate has rigidity with excellent impact resistance and excellent flatness, and thus can be said to be a non-magnetic substrate suitable for high recording density. If magnetic anisotropy in the circumferential direction can be imparted to a magnetic recording medium using glass for the non-magnetic substrate, it is expected that excellent electromagnetic conversion characteristics can be obtained.
[0008]
Several methods are known for forming a texture streak by subjecting a glass substrate to mechanical texture processing. For example, in order to form fine and uniform texture streaks, it has been proposed to use a woven fabric tape composed of an abrasive suspension containing a solution having a hydroxyl group and a plastic fiber (for example, see Patent Document 1). .).
[0009]
Also, in order to form fine and uniform texture streaks, diamond abrasive grains and CeO 2 It has been proposed to use abrasive grains together (see, for example, Patent Document 2).
[0010]
However, it is difficult for the glass substrate to impart sufficient magnetic anisotropy in the circumferential direction only by forming texture streaks. Therefore, it has been proposed to form an amorphous layer containing at least Ni and P by sputtering in order to impart circumferential magnetic anisotropy to a glass substrate having a linear texture formed on the surface thereof ( For example, see Patent Document 3.)
[0011]
[Patent Document 1]
Patent No. 3117438
[0012]
[Patent Document 2]
U.S. Pat. No. 6,248,395
[0013]
[Patent Document 3]
JP 2001-209927 A
[0014]
[Problems to be solved by the invention]
Forming an amorphous layer containing at least Ni and P on a glass substrate on which texture streaks are formed is an attempt to create the same situation as an aluminum substrate plated with NiP. Magnetic anisotropy appears when a Cr-based underlayer, a Co-based magnetic layer, and a protective film are sequentially formed by this method. However, when an amorphous layer containing at least Ni and P is used, it is difficult to obtain a high coercive force and a high squareness ratio, and good electromagnetic conversion characteristics cannot be obtained.
[0015]
The present invention has been made in view of the above circumstances. The present invention relates to a magnetic recording medium having circumferential magnetic anisotropy, high coercive force, high squareness ratio and good electromagnetic conversion characteristics using a glass substrate having a streak formed on the surface, and a method of manufacturing the same. And a magnetic recording / reproducing apparatus.
[0016]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve the above-mentioned problems. As a result, the orientation adjusting layer has at least one selected from the group consisting of Co, Ni and Fe and any one selected from the group consisting of W, Mo, Ta and Nb. The present inventors have found that the characteristics of a magnetic recording / reproducing apparatus can be improved by using an alloy layer composed of one or more kinds of components, and completed the present invention. That is, the present invention relates to the following.
[0017]
(1) In a magnetic recording medium having an alignment adjusting layer, a non-magnetic underlayer, a magnetic layer and a protective film in this order on a glass substrate having a streak on the surface, the alignment adjusting layer is selected from Co, Ni and Fe. A magnetic recording medium comprising at least one kind selected from the group consisting of W, Mo, Ta and Nb.
[0018]
(2) The alignment adjustment layer is made of a Co-W alloy, a Co-Mo alloy, a Co-Ta alloy, a Co-Nb alloy, a Ni-Ta alloy, a Ni-Nb alloy, or a Fe-W alloy. (1) The magnetic recording medium according to (1), comprising at least one alloy selected from the group consisting of Fe, Mo-based alloy, and Fe-Nb-based alloy.
[0019]
(3) The magnetic recording medium according to (1) or (2), wherein the thickness of the alignment adjusting film is in a range of 10 Å to 300 Å.
[0020]
(4) The magnetic recording medium according to any one of (1) to (3), wherein the glass substrate is an amorphous glass.
[0021]
(5) The magnetic recording medium according to any one of (1) to (4), wherein the linear density of the streaks is 7500 (lines / mm) or more.
[0022]
(6) The magnetic layer according to any one of (1) to (5), wherein a magnetic anisotropy index (retention force in a circumferential direction / retention force in a radial direction) of the magnetic layer is 1.05 or more. Item 7. The magnetic recording medium according to Item 1.
[0023]
(7) The magnetic recording medium according to (1) to (6), wherein the magnetic anisotropy index of the residual magnetization (the residual magnetization in the circumferential direction / the residual magnetization in the radial direction) is 1.05 or more. The magnetic recording medium according to claim 1.
[0024]
(8) The non-magnetic underlayer includes a Cr layer or a Cr alloy layer containing at least one selected from Ti, Mo, Al, Ta, W, Ni, B, Si and V. The magnetic recording medium according to any one of (1) to (7).
[0025]
(9) The magnetic layer is made of a Co-Cr-Pt-based alloy, a Co-Cr-Pt-Ta-based alloy, a Co-Cr-Pt-B-based alloy, or a Co-Cr-Pt-BY-based alloy (Y is Ta Or Cu.) The magnetic recording medium according to any one of (1) to (8), wherein the magnetic recording medium includes at least one selected from the group consisting of:
[0026]
(10) A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to any one of (1) to (9); and a magnetic head for recording / reproducing information on / from the magnetic recording medium.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
The magnetic recording medium of the present invention is a magnetic recording medium having an alignment adjusting layer, a non-magnetic underlayer, a magnetic layer, and a protective film in this order on a glass substrate having a streak on the surface. And one or more selected from W, Mo, Ta and Nb.
[0028]
FIG. 1 schematically shows an embodiment of the magnetic recording medium of the present invention, wherein 1 is a glass substrate, 2 is an alignment adjusting film, 3 is a non-magnetic underlayer, 4 is a magnetic layer, and 5 is a protection layer. Show the membrane.
[0029]
Examples of the glass used for the glass substrate 1 include amorphous glass and crystallized glass. As the amorphous glass, general-purpose soda lime glass, aluminoborosilicate glass, and aluminosilicate glass can be used. As the crystallized glass, lithium-based crystallized glass can be used. In particular, it is preferable to use amorphous glass having uniform physical properties such as hardness, since a uniform texture can be applied to the surface.
[0030]
Streaks are formed on the surface of the glass substrate 1 by, for example, lapping tape using fixed abrasive grains or mechanical texture processing using free abrasive grains. The striations formed on the surface of the glass substrate 1 are preferably along the circumferential direction of the substrate. The surface average roughness Ra of the glass substrate 1 on which the streaks are formed is in the range of 0.1 nm to 1 nm (1 Å to 10 Å), preferably 0.2 nm to 0.8 nm (2 Å to 8 Å). It is desirable to be within.
[0031]
When the surface average roughness Ra is less than 0.1 nm, the glass substrate 1 becomes excessively smooth, and the effect of increasing the magnetic anisotropy of the magnetic film 4 is reduced. On the other hand, when the surface average roughness Ra exceeds 1 nm, the smoothness of the medium surface is reduced, the glide height characteristics are reduced, and it is difficult to reduce the flying height of the magnetic head during recording and reproduction.
[0032]
The surface of the glass substrate 1 preferably has streaks having a linear density of 7500 (lines / mm) or more. The linear density is measured in the radial direction of the glass substrate. The reason why the linear density is set to 7500 (lines / mm) or more is that the effect of the streaks is the effect of improving the magnetic characteristics (for example, the effect of improving the coercive force), the electromagnetic conversion characteristics (for example, the SNR (Signal to Noise Ratio), and the effect of improving the PW50. )). More preferably, if the linear density has a streak of 20,000 (lines / mm) or more, the above-described effect becomes more remarkable.
[0033]
Note that the upper limit of the linear density is 200000 (lines / mm). If the linear density exceeds 200000 (lines / mm), the line spacing between the streaks will be less than 50 angstroms, the particle size of the non-magnetic underlayer will be larger, and the magnetic anisotropy of the magnetic recording medium will decrease. Let it.
[0034]
The striations preferably have a predominantly circumferential direction with respect to the substrate. Here, the streak refers to a surface in which a height distance between a peak and a valley in a radial cross section is in a range of 0.02 nm to 20 nm (more preferably, in a range of 0.05 nm to 10 nm). Is the uneven shape. This is because the magnetic anisotropy due to the surface unevenness in this range is effective for improving the electromagnetic conversion characteristics. In addition, the streaks exceeding 20 nm may affect the uniformity of the nearby streaks because the unevenness is too large.
[0035]
The striations are preferably formed by, for example, lapping tape using fixed abrasive grains or mechanical texture processing using free abrasive grains.
[0036]
The linear density of the streaks can be measured using, for example, an AFM (Atomic Force Microscope, manufactured by Digital Instrument, USA).
[0037]
The measurement conditions of the linear density are as follows. The scan width is 1 μm, the scan rate is 1 Hz, the number of measurements is 256, and the mode is a tapping mode. The probe is scanned in the radial direction of a glass substrate as a sample, and an AFM scan image is obtained. A Plan FitAuto process, which is one of the smoothing processes, is performed on the X-axis and the Y-axis of the Scan image by setting the order of the Flatten Order to 2, and the image is smoothed and corrected. A box of about 0.5 μm × about 0.5 μm is set for the image after the smoothing correction, and the line density in that range is calculated. The linear density is calculated by converting the total number of zero-crossing points along both the X-axis center line and the Y-axis center line into 1 mm. That is, the linear density is the number of peaks and valleys of texture streaks per 1 mm in the radial direction.
[0038]
Each point in the sample surface is measured, and the average value and standard deviation of the measured values are obtained. The average value is defined as the linear density of the streaks on the glass substrate. The number of measurement points can be a number for which an average value and a standard deviation can be obtained. For example, the number of measurements can be 10 points. When the average value and the standard deviation are calculated at eight points excluding the maximum value and the minimum value, the measurement abnormal value can be removed, so that the measurement accuracy can be improved.
[0039]
The orientation adjusting film 2 adjusts the crystal orientation of the non-magnetic base film 3 formed immediately above, further adjusts the crystal orientation of the magnetic film 4 formed thereon, and adjusts the crystal orientation of the magnetic film 4 in the circumferential direction. This is for improving magnetic anisotropy. The orientation adjusting film 2 not only adjusts the crystal orientation, but also functions as a crystal grain refinement film that refines crystal grains in the non-magnetic underlayer 3 and the magnetic film 4.
For the orientation adjusting film 2, an alloy layer composed of at least one kind of component selected from Co, Ni and Fe and at least one kind of component selected from W, Mo, Ta and Nb may be used. I can do it.
[0040]
The composition of the alloy layer used for the above-mentioned alignment adjustment film 2 is not particularly limited. However, preferably, the total content of Co, Ni and Fe is in the range of 25 at% to 70 at%, and the total content of W, Mo, Ta and Nb is in the range of 30 at% to 75 at%. desirable. If the total content of Co, Ni and Fe is less than 25 at%, the crystal orientation of the nonmagnetic underlayer is not sufficient, and the coercive force is reduced. If the total content of Co, Ni and Fe exceeds 70 at%, the orientation adjusting film has magnetization, which is not preferable. If the total content of Mo, Ta, and Nb is less than 30 at%, the magnetic anisotropy in the circumferential direction of the magnetic film decreases. When the total content of Mo, Ta, and Nb exceeds 75 at%, the crystal orientation of the nonmagnetic underlayer is not sufficient, and the coercive force is reduced.
[0041]
The above-mentioned alignment adjusting film 2 is more preferably made of a Co-W-based alloy, a Co-Mo-based alloy, a Co-Ta-based alloy, a Co-Nb-based alloy, a Ni-Ta-based alloy, a Ni-Nb-based alloy, a Fe- It is desirable to use at least one alloy layer selected from a W-based alloy, an Fe-Mo-based alloy, and an Fe-Nb-based alloy. The present inventors have made intensive efforts and found that the use of an alloy containing the Fe7W6 structure further improves the magnetic anisotropy in the circumferential direction of the magnetic film. The composition range of these alloy layers containing 25% or more of the Fe7W6 structure is effective for further improving the magnetic anisotropy in the circumferential direction of the magnetic film. That is, the composition range of W in the CoW alloy is preferably 30 at% to 85 at%. The Mo composition range of the CoMo alloy is preferably 30 at% to 85 at%. The composition range of Ta in the CoTa-based alloy is preferably from 38 at% to 65 at%. The composition range of Nb in the CoNb-based alloy is preferably from 37 at% to 86 at%. The composition range of Ta of the NiTa-based alloy is preferably from 38 at% to 63 at%. The composition range of Nb in the NiNb-based alloy is preferably from 31 at% to 86 at%. The composition range of W in the Fe-W alloy is preferably from 37 at% to 86 at%. The composition range of Mo in the Fe—Mo alloy is preferably 35 at% to 85 at%. The composition range of Nb in the Fe—Nb alloy is preferably 40 at% to 86 at%.
[0042]
Co-W based alloy, Co-Mo based alloy, Co-Ta based alloy, Co-Nb based alloy, Ni-Ta based alloy, Ni-Nb based alloy, Fe-W based alloy, Fe-Mo based alloy, Fe- Each of the Nb-based alloys exerts its properties even when used alone, and an alloy in which some of them are combined exhibits similar properties. For example, a Co-W-Mo-based alloy, a Co-Ni-Nb-based alloy, a Co-W-Mo-Ta-based alloy, etc. exhibit similar characteristics.
[0043]
In the present invention, the thickness of the alignment adjusting film is preferably in the range of 10 Å to 300 Å. If the thickness of the orientation adjusting film is less than 10 Å, the crystal orientation of the nonmagnetic underlayer is not sufficient, and the coercive force is reduced. If the thickness of the orientation adjusting film exceeds 300 angstroms, the magnetic anisotropy in the circumferential direction of the magnetic film decreases. More preferably, the thickness of the orientation adjusting film is in the range of 20 Å to 100 Å in order to increase the magnetic anisotropy in the circumferential direction of the magnetic film.
[0044]
An element having an auxiliary effect may be added to the alignment adjusting film in the present invention. Examples of the additional element include Ti, V, Cr, Mn, Zr, Hf, Ru, B, Al, Si, P and the like. The total content of the additional elements is preferably 20 at% or less. If the total content exceeds 20 at%, the effect of the above-mentioned alignment adjusting film is reduced. The lower limit of the total content is 0.1 at%, and if the content is less than 0.1 at%, the effect of the added element is lost.
[0045]
As the nonmagnetic underlayer 3, a Cr layer or a Cr alloy layer composed of Cr and one or more kinds selected from Ti, Mo, Al, Ta, W, Ni, B, Si and V can be used. preferable.
[0046]
Since the lattice constant of the Cr layer is small, the lattice constant of Cr is increased by adding Mo, W, V, Ti or the like, as in the case of a Cr-Mo, Cr-W, Cr-V, or Cr-Ti alloy. It is preferable to match the lattice constant with the Co alloy of the magnetic layer from the viewpoint of improving the SNR characteristics of the magnetic recording medium.
[0047]
The addition of B to the above-described Cr layer or Cr alloy layer is effective for crystal refinement, and is preferable from the viewpoint of improving the SNR characteristics of the magnetic recording medium.
[0048]
Regarding the crystal orientation of the Cr layer or Cr alloy layer of the nonmagnetic underlayer 3, it is preferable that the (100) plane be the preferential orientation plane. As a result, since the crystal orientation of the Co alloy of the magnetic layer formed on the nonmagnetic underlayer is stronger (11.0), the magnetic properties such as the coercive force (Hc) are improved, and the recording / reproducing properties such as the SNR are improved. Is obtained.
[0049]
In addition, “•” in the crystal plane notation indicates an abbreviation of the Miller-Brabé index indicating the crystal plane. That is, in a hexagonal system such as Co to represent a crystal plane, it is usually represented by (hkil) and four indices. Among them, "i" is defined as i =-(h + k). In a format in which the part of “i” is omitted, it is described as (hk · l).
[0050]
The magnetic layer 4 is preferably a Co alloy mainly composed of Co whose lattice is sufficiently well matched to, for example, the (100) plane of the nonmagnetic underlayer immediately below, and is preferably a material having an hcp structure. For example, it is selected from Co-Cr-Ta-based, Co-Cr-Pt-based, Co-Cr-Pt-Ta-based, Co-Cr-Pt-B-Ta-based, and Co-Cr-Pt-B-Cu-based alloys. It is preferable to include any one of them.
[0051]
For example, in the case of a Co—Cr—Pt-based alloy, it is preferable that the Cr content be in the range of 10 at% to 25 at% and the Pt content be in the range of 8 at% to 16 at% from the viewpoint of improving the SNR.
[0052]
For example, in the case of a Co-Cr-Pt-B-based alloy, the Cr content is in the range of 10 at% to 25 at%, the Pt content is in the range of 8 at% to 16 at%, and the B content is 1 at% to It is preferable to be within the range of 20 at% from the viewpoint of improving the SNR.
[0053]
For example, in the case of a Co-Cr-Pt-B-Ta alloy, the content of Cr is in a range of 10 at% to 25 at%, the content of Pt is in a range of 8 to 16 at%, and the content of B is 1 at%. % To 20 at%, and the Ta content is preferably in a range of 1 at% to 4 at% from the viewpoint of improving the SNR.
[0054]
For example, in the case of a Co-Cr-Pt-B-Cu alloy, the Cr content is in the range of 10 at% to 25 at%, the Pt content is in the range of 8 at% to 16 at%, and the B content is 2 at%. % To 20 at%, and the Cu content is preferably in the range of 1 at% to 4 at% from the viewpoint of improving the SNR.
[0055]
If the thickness of the magnetic layer 4 is 15 nm or more, there is no problem from the viewpoint of thermal fluctuation, but it is preferably 40 nm or less from the demand for high recording density. If the thickness exceeds 40 nm, the crystal grain size of the magnetic layer increases, and favorable recording / reproducing characteristics cannot be obtained. The magnetic layer may have a multilayer structure, and the material thereof may be a combination using any one of the above. In the case of a multilayer structure, the layer immediately above the nonmagnetic underlayer is made of a Co-Cr-Pt-B-Ta alloy, a Co-Cr-Pt-B-Cu alloy, or a Co-Cr-Pt-B alloy. Is preferable from the viewpoint of improving the SNR characteristics of the recording / reproducing characteristics. The uppermost layer is preferably made of a Co-Cr-Pt-B-Cu-based alloy or a Co-Cr-Pt-B-based alloy from the viewpoint of improving the recording / reproducing characteristics and the SNR characteristics.
[0056]
It is preferable to provide a nonmagnetic intermediate layer between the nonmagnetic underlayer 3 and the magnetic layer 4 for the purpose of promoting epitaxial growth of a Co alloy. The effect of improving magnetic characteristics such as coercive force and the effect of improving recording / reproducing characteristics such as SNR can be obtained. The non-magnetic intermediate layer may contain Co and Cr. When a Co—Cr alloy is used, the content of Cr is preferably in the range of 25 at% to 45 at% from the viewpoint of improving the SNR. The thickness of the nonmagnetic intermediate layer is preferably in the range of 0.5 nm to 3 nm from the viewpoint of improving the SNR.
[0057]
An antiferromagnetic coupling layer may be provided between the nonmagnetic underlayer 3 and the magnetic layer 4 in order to improve the thermal demagnetization of the magnetic recording medium. The antiferromagnetic coupling layer is formed from a stabilizing layer and a nonmagnetic coupling layer. For the stabilizing layer, use a magnetic Co-Ru alloy, Co-Cr alloy, Co-Cr-Pt alloy, Co-Cr-Pt-B alloy, Co-Cr-Ta alloy, etc. Can be. It is preferable to use Ru for the non-magnetic coupling layer. It is preferable that the Ru film thickness is about 0.8 nm because the antiferromagnetic coupling strength has a maximum value.
[0058]
When the magnetic layer 4 contains B, it is preferable that the Cr concentration in the region where the B concentration is 1 at% or more is 40 at% or less near the boundary between the nonmagnetic underlayer and the magnetic layer. This is because Cr and B can be prevented from coexisting at a high concentration, and the generation of a covalent compound of Cr and B can be suppressed as much as possible. As a result, a decrease in the orientation in the magnetic layer can be prevented.
[0059]
The protective film 5 can be made of a conventionally known material, for example, a simple substance of carbon or SiC or a material containing these as a main component. The thickness of the protective film is preferably in the range of 1 nm to 10 nm from the viewpoint of reduction of magnetic spacing or durability when used in a high recording density state. Magnetic spacing refers to the distance between the read / write element of the head and the magnetic layer. The electromagnetic conversion characteristics improve as the magnetic spacing decreases. Since the protective film exists between the read / write element of the head and the magnetic layer, it becomes a factor for expanding the magnetic spacing.
[0060]
If necessary, a lubricating layer made of, for example, a perfluoropolyether fluorine-based lubricant can be provided on the protective film 5.
[0061]
The magnetic layer of the magnetic recording medium of the present invention preferably has a magnetic anisotropy index (OR) of 1.05 or more (more preferably 1.1 or more). The magnetic anisotropy index is represented by (circumferential holding force / radial holding force).
[0062]
When the magnetic anisotropy index is 1.05 or more, the effect of improving magnetic properties such as coercive force and the effect of improving electromagnetic conversion properties such as SNR and PW50 can be obtained. The magnetic anisotropy index is defined as the ratio of the coercive force (Hc) in the circumferential direction to the coercive force in the radial direction. However, since the coercive force of the magnetic recording medium is increased, the magnetic anisotropy index becomes higher. Sometimes measured too low.
[0063]
In the present invention, in order to supplement this point, the magnetic anisotropy index of the residual magnetization is also used. The magnetic anisotropy index (MrtOR) of the remanent magnetization is defined as the ratio of the remanent magnetization (Mrt) in the circumferential direction to the remanent magnetization (Mrt) in the radial direction (MrtOR = Mrt in the circumferential direction / Mrt in the radial direction). (Mrt). When the magnetic anisotropy index of the residual magnetization amount is 1.05 or more, more preferably 1.1 or more, the effect of improving magnetic properties such as coercive force and the effect of improving electromagnetic conversion properties such as SNR and PW50 are obtained. Can be
[0064]
Note that the upper limit of the values of OR and MrrtOR is ideally when all the magnetic domains of the magnetic film are oriented in the circumferential direction. In this case, the denominator of the magnetic anisotropy index is 0, and Become.
[0065]
A VSM (Vibrating Sample Magnetometer) is used for measuring the magnetic anisotropy index and the magnetic anisotropy index of the residual magnetization.
[0066]
FIG. 2 shows an example of a magnetic recording / reproducing apparatus using the above magnetic recording medium. The magnetic recording / reproducing apparatus shown here includes a magnetic recording medium 20 having the configuration shown in FIG. 1, a medium driving unit 21 for driving the magnetic recording medium 20 to rotate, a magnetic head 22 for recording / reproducing information on / from the magnetic recording medium 20, A head drive unit 23 for moving the magnetic head 22 relative to the magnetic recording medium 20 and a recording / reproducing signal processing system 24 are provided. The recording / reproducing signal processing system 24 processes data input from the outside and sends a recording signal to the magnetic head 22, or processes a reproducing signal from the magnetic head 22 and sends the data to the outside. I can do it. The magnetic head 22 used in the magnetic recording / reproducing apparatus of the present invention includes not only a magnetoresistive (MR) element using an anisotropic magnetoresistive effect (AMR) as a reproducing element but also a GMR using a giant magnetoresistive effect (GMR). It is possible to use a head having elements and the like and suitable for higher recording density.
[0067]
Further, the magnetic recording / reproducing apparatus of the present invention is a magnetic recording / reproducing apparatus which is inexpensive and has a high recording density because a magnetic recording medium manufactured by directly texturing a glass substrate is used.
[0068]
Further, the magnetic recording / reproducing apparatus of the present invention uses a magnetic recording medium having a small average roughness and a small undulation, so that in addition to improving the electromagnetic conversion characteristics, the magnetic recording / reproducing apparatus can reduce spacing loss. The magnetic recording / reproducing apparatus has good error characteristics even when the head is used in a low flying state.
[0069]
According to the magnetic recording / reproducing apparatus, it is possible to manufacture a magnetic recording / reproducing apparatus suitable for high recording density.
[0070]
Next, an example of the production method of the present invention will be described.
[0071]
Either amorphous glass or crystallized glass can be used as the glass substrate. For example, amorphous glass is preferably used because, for example, when texture processing is performed, streaks enter more uniformly.
[0072]
It is desirable that the glass substrate has an average surface roughness Ra of 2 nm (20 angstroms) or less, preferably 1 nm or less.
[0073]
Further, it is preferable that the minute waviness (Wa) of the surface is 0.3 nm or less (more preferably, 0.25 nm or less). It is preferable for the flight stability of the magnetic head to use at least one of the chamfered part and the side part of the chamfered part of the end face having a surface average roughness Ra of 10 nm or less (more preferably 9.5 nm or less). . The minute waviness (Wa) can be measured as a surface average roughness in a measurement range of 80 μm using, for example, a surface roughness measuring device P-12 (manufactured by KLM-Tencor).
[0074]
First, the surface of the glass substrate is textured so as to form streaks having a linear density of 7500 (lines / mm) or more. For example, mechanical processing using fixed abrasive grains and / or free abrasive grains on the surface of a glass substrate such that a texture streak having a linear density of 7500 (lines / mm) or more is formed on the surface of the glass substrate (“ Texture is also applied in the circumferential direction by "mechanical texture processing." For example, a polishing tape is pressed against and brought into contact with the surface of the substrate, a polishing slurry containing abrasive grains is supplied between the substrate and the polishing tape, and when the substrate is rotated, texturing is performed by sending the polishing tape. Do it. The rotation of the substrate can be in the range from 200 rpm to 1000 rpm. The supply amount of the polishing slurry can be in the range of 10 ml / min to 100 ml / min. The feed speed of the polishing tape can be in the range of 1.5 mm / min to 150 mm / min. The particle size of the abrasive grains contained in the polishing slurry can be 0.05 μm to 0.3 μm as D90 (particle size value when the cumulative mass% corresponds to 90 mass%). The pressing force of the tape can be in the range of 1 kgf to 15 kgf (9.8 N to 147 N). These conditions are preferably set so as to form a texture streak having a linear density of 7,500 (lines / mm) or more (more preferably, 20,000 (lines / mm) or more).
[0075]
The surface average roughness Ra of the glass substrate 1 on which the texture streaks are formed is in the range of 0.1 nm to 1 nm (1 Å to 10 Å), preferably 0.2 nm to 0.8 nm (2 Å to 8 Å). It is desirable to be within.
[0076]
Texture processing with oscillation can be applied. Oscillation is an operation in which the tape is run in the circumferential direction of the substrate and, at the same time, the tape is rocked in the radial direction of the substrate. The oscillation condition is preferably set to 60 times / minute to 1200 times / minute.
[0077]
As a method of the texture processing, a method of forming a texture streak having a linear density of 7500 (lines / mm) or more can be used. In addition to the method using the mechanical texture described above, a method using fixed abrasive grains, a method using a fixed grindstone, The method used and the method using laser processing can be used.
[0078]
The sputtering conditions for forming the film are, for example, as follows. The degree of vacuum is 10 in the chamber used for formation. -4 Pa-10 -7 Exhaust until the pressure falls within the range of Pa. A glass substrate having a texture streak formed on its surface is accommodated in a chamber, and an Ar gas is introduced as a sputtering gas and discharged to form a sputter film. At this time, the supplied power is in the range of 0.2 kW to 2.0 kW, and a desired film thickness can be obtained by adjusting the discharge time and the supplied power.
[0079]
Preferably, a step of exposing the surface to an oxygen atmosphere is provided between the orientation adjusting film and the nonmagnetic underlayer. The oxygen atmosphere to be exposed is, for example, 5 × 10 -4 It is preferable to use an atmosphere containing an oxygen gas of Pa or more. Alternatively, a gas in which an atmosphere gas for exposure is brought into contact with water can be used. The exposure time is preferably in the range of 0.5 seconds to 15 seconds. For example, it is preferable to take out the orientation adjusting film from the chamber after the formation and expose the film to an outside air atmosphere or an oxygen atmosphere. Alternatively, it is also preferable to use a method in which air or oxygen is introduced into the chamber and exposed without removing the chamber from the chamber. In particular, the method of exposing in the chamber does not require a complicated process such as taking out from a vacuum chamber, so that the process can be continuously performed as a series of film forming processes including the formation of the nonmagnetic underlayer and the magnetic layer. preferable. In that case, for example, the ultimate vacuum degree is 10 -6 5 × 10 below Pa -4 It is preferable to use an atmosphere containing an oxygen gas of Pa or more. The upper limit of the oxygen gas pressure at the time of exposure with oxygen is, although exposure at atmospheric pressure is possible, preferably 5 × 10 -2 It is better to be Pa or less.
[0080]
By heating the glass substrate, the crystal orientation of the non-magnetic underlayer and the magnetic layer can be improved. The heating temperature of the glass substrate is preferably in the range of 100C to 400C. It is more preferable to heat after forming the alignment adjusting film.
[0081]
After the formation of the nonmagnetic underlayer, a magnetic layer having a thickness of 15 nm to 40 nm is similarly formed by a sputtering method using a sputtering target made of the material of the magnetic layer. Sputtering targets are Co-Cr-Ta, Co-Cr-Pt, Co-Cr-Pt-Ta, Co-Cr-Pt-B-Ta, Co-Cr-Pt-B-Cu. And those containing any one selected from the group consisting of: For example, in the case of a Co—Cr—Pt-based alloy, the Cr content can be in the range of 10 at% to 25 at%, and the Pt content can be in the range of 8 at% to 16 at%. For example, in the case of a Co—Cr—Pt—B—Ta alloy, the Cr content is in the range of 16 at% to 24 at%, the Pt content is in the range of 8 at% to 16 at%, and the B content is 2 at%. % To 8 at%, and the Ta content can be in a range of 1 at% to 4 at%. For example, in the case of a Co-Cr-Pt-B-Cu alloy, the Cr content is in the range of 16 at% to 24 at%, the Pt content is in the range of 8 at% to 16 at%, and the B content is 2 at%. % To 8 at%, and the Cu content can be in the range of 1 at% to 4 at%.
[0082]
Here, the crystal orientation of Cr or the Cr alloy of the nonmagnetic underlayer is preferably formed such that the preferential orientation plane indicates (100).
[0083]
When a non-magnetic intermediate layer is provided between the non-magnetic underlayer and the magnetic layer, a sputtering target using a Co-Cr-based alloy (Cr content is in the range of 25 to 45 at%) as a raw material. It is preferable to use At this time, when B is contained in the magnetic layer, the sputtering is performed under such a sputtering condition that the Cr concentration in the region where the B concentration is 1 at% or more and the Cr concentration is 40 at% or less near the boundary between the nonmagnetic underlayer and the magnetic layer. It is preferred to film.
[0084]
After forming the magnetic layer, a protective film, for example, a protective film containing carbon as a main component, is formed by a known method, for example, a sputtering method, a plasma CVD method, or a combination thereof.
[0085]
Further, if necessary, a perfluoropolyether fluorine-based lubricant is applied on the protective film by using a dipping method, a spin coating method or the like to form a lubricating layer.
[0086]
【Example】
(Example 1)
Amorphous glass GD-7 manufactured by Nippon Sheet Glass was used for the glass substrate. The size of the glass substrate is an outer diameter of 65 mm, an inner diameter of 20 mm, and a plate thickness of 0.635 mm.
[0087]
The glass substrate was subjected to mechanical texture processing. The conditions of the mechanical texture processing are as follows. As abrasive grains contained in the slurry, diamond abrasive grains having a D90 of 0.15 μm were used. The slurry was dropped at 50 ml / min for 2 seconds before processing started. A woven cloth made of polyester was used for the polishing tape. The feed of the polishing tape was 75 mm / min. The rotation speed of the disk was 600 rpm. The disk was rocked at 120 times / minute. The pressing force of the tape was 2.0 kgf (19.6 N). The processing time was 10 seconds. When the substrate surface was measured by AFM manufactured by Digital Instrument, a glass substrate having texture streaks having an average roughness Ra of 4 angstroms and a linear density of 25,000 lines / mm was obtained.
[0088]
After sufficiently washing and drying the substrate, it was set in a DC magnetron sputtering apparatus (C3010 manufactured by Anelva (Japan)). 2 × 10 vacuum reach -7 Torr (2.7 × 10 -5 After evacuation to Pa), a 1 nm lamination was performed at room temperature using a target made of a Co—W alloy (Co: 45 at%, W: 55 at%) as an alignment adjusting film.
[0089]
Thereafter, the substrate was heated to 250 ° C. After the heating, oxygen exposure was performed at 0.05 Pa for 5 seconds. As a nonmagnetic underlayer, a target made of a Cr-Ti-B alloy (Cr: 83 at%, Ti: 15 at%, B: 2 at%) was laminated to a thickness of 8 nm. The nonmagnetic intermediate layer was laminated to a thickness of 2 nm using a target made of a Co—Cr alloy (Co: 65 at%, Cr: 35 at%). A target made of a Co—Cr—Pt—B alloy (Co: 60 at%, Cr: 22 at%, Pt: 12 at%, B: 6 at%) is used as the magnetic layer, and the CoCrPtB alloy layer as the magnetic layer is formed to a thickness of 20 nm. A protective film (carbon) having a thickness of 5 nm was laminated. The Ar pressure during film formation was 3 mTorr (0.4 Pa). 20 nm of a lubricant composed of perfluoropolyether was applied by a dipping method to form a lubricating layer.
[0090]
Thereafter, a glide test was performed using a glide tester with a glide height of 0.4 μ inch under test conditions, and passed magnetic recording media were recorded using a read-write analyzer RWA1632 (manufactured by GUZIK (USA)). The reproduction characteristics were examined. The recording / reproducing characteristics were measured for electromagnetic conversion characteristics such as a reproduction signal output (TAA), a half-width of a solitary wave reproduction output (PW50), SNR, and overwrite (OW). For evaluation of the recording / reproducing characteristics, a composite thin-film magnetic recording head having a giant magnetoresistive (GMR) element in the reproducing section was used. The noise was measured by measuring the integrated noise from 1 MHz to a frequency corresponding to 375 kFCI when a 500 kFCI pattern signal was written. The reproduction output was measured at 250 kFCI, and calculated as SNR = 20 × log (reproduction output / 1 integrated noise from 1 MHz to 375 kFCI equivalent frequency). For measurement of coercive force (Hc) and squareness ratio (S *), a car effect type magnetic property measuring device (RO1900, manufactured by Hitachi Electronics Engineering, Ltd. (Japan)) was used. VSM (BHV-35, manufactured by Riken Denshi Co., Japan) was used for measurement of the magnetic anisotropy index (OR) and the magnetic anisotropy index (MrtOR) of the residual magnetization.
[0091]
(Examples 2 to 33)
The same treatment as in Example 1 was performed except that the alloy composition and the film thickness of the orientation adjusting film were as shown in Table 1.
[0092]
(Example 34)
As an alignment adjusting film, a target made of a Co-W alloy (Co: 45 at%, W: 55 at%) was also laminated at a normal temperature by 5 nm. An antiferromagnetic coupling layer was provided instead of the nonmagnetic intermediate layer. The stabilizing layer was laminated to a thickness of 2 nm using a target made of a Co-Ru alloy (Co: 80 at%, Ru: 20 at%). The non-magnetic coupling layer was formed to have a thickness of 0.8 nm by using a target made of Ru. Except for this, the same processing as in Example 1 was performed.
[0093]
(Comparative Examples 1 to 33)
The same processing as in Example 1 was performed except that the mechanical texture was not applied to the glass substrate, and the alloy composition and the film thickness of the alignment adjusting film were as shown in Table 2.
[0094]
(Comparative Examples 34 to 36)
The same treatment as in Example 1 was performed, except that the alloy composition and the film thickness of the orientation adjusting film were as shown in Table 2.
[0095]
Coercive force (Hc), squareness ratio, magnetic anisotropy index (OR), magnetic anisotropy index of residual magnetization (MrtOR), electromagnetic conversion characteristics of Examples 1 to 33 and Comparative Examples 1 to 36 Tables 1 and 2 show the results. Examples 1 to 7 show the tendency of the thickness of the orientation adjustment film Co—W-based alloy (Co: 45 at%, W: 55 at%). Good magnetic anisotropy in the circumferential direction is obtained when the film thickness is in the range of 25 to 300 angstroms, and the electromagnetic conversion characteristics are excellent. Further, when the film thickness is in the range of 25 to 100 angstroms, more favorable circumferential magnetic anisotropy is obtained, and the electromagnetic conversion characteristics are excellent. In Examples 8 to 30, the alloy composition of the orientation adjusting film was changed. Co-W based alloy, Co-Mo based alloy, Co-Ta based alloy, Co-Nb based alloy, Ni-Ta based alloy, Ni-Nb based alloy, Fe-W based alloy, Fe-Mo based alloy, Fe- Good circumferential magnetic anisotropy is obtained with an Nb-based alloy, and the recording / reproducing characteristics are excellent. In Examples 31 to 33, a ternary alloy was used for the alignment adjusting film. Co-W-Mo alloys, Co-W-Ta alloys, and Co-Ni-W alloys have good magnetic anisotropy in the circumferential direction, and have excellent electromagnetic conversion characteristics.
[0096]
In Comparative Examples 1 to 33, a glass substrate having no texture streaks formed on the surface was used, and the alloy composition of the alignment adjusting film in Examples 1 to 33 was used. Since no texture streaks are formed on the surface, none of them exhibit magnetic anisotropy. It can be seen that the electromagnetic conversion characteristics are also inferior to those of the examples.
[0097]
In Comparative Examples 34 to 36, a Ni—P-based alloy (Ni: 80 at%, P: 20 at%) was used as an alignment adjusting film on a glass substrate having texture streaks formed on the surface. Although magnetic anisotropy in the circumferential direction is exhibited, good electromagnetic conversion characteristics have not been obtained due to low coercive force and squareness.
[0098]
[Table 1]
[0099]
[Table 2]
[0100]
【The invention's effect】
The magnetic recording medium of the present invention is a magnetic recording medium having at least a glass substrate on which circumferential grooves are formed, an alignment adjusting layer, a non-magnetic underlayer, a magnetic layer, and a protective film in this order. A magnetic recording characterized in that the layer includes an alloy layer composed of one or more components selected from Co, Ni and Fe and one or more components selected from W, Mo, Ta and Nb. Since the medium is a medium, magnetic anisotropy in the circumferential direction is exhibited, and electromagnetic conversion characteristics are improved. As a result, a magnetic recording medium suitable for high recording density is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a magnetic recording medium of the present invention.
FIG. 2 shows a magnetic recording / reproducing apparatus using the magnetic recording medium of the present invention.
[Explanation of symbols]
1 Glass substrate
2 Alignment adjustment film
3 Non-magnetic underlayer
4 Magnetic layer
5 Protective film
20 Magnetic recording media
21 Medium drive unit
22 Magnetic head
23 Head drive unit
24 Recording / playback signal processing system

Claims (10)

  1. In a magnetic recording medium having an alignment adjusting layer, a non-magnetic underlayer, a magnetic layer and a protective film in this order on a glass substrate having a streak on its surface, the alignment adjusting layer is selected from Co, Ni and Fe. A magnetic recording medium comprising at least one kind and any one or more kinds selected from W, Mo, Ta and Nb.
  2. The orientation adjustment layer is made of a Co-W alloy, a Co-Mo alloy, a Co-Ta alloy, a Co-Nb alloy, a Ni-Ta alloy, a Ni-Nb alloy, a Fe-W alloy, or a Fe- alloy. 2. The magnetic recording medium according to claim 1, comprising at least one alloy selected from a Mo-based alloy and an Fe-Nb-based alloy.
  3. 3. The magnetic recording medium according to claim 1, wherein the thickness of the alignment adjusting film is in a range of 10 Å to 300 Å.
  4. The magnetic recording medium according to claim 1, wherein the glass substrate is an amorphous glass.
  5. The magnetic recording medium according to any one of claims 1 to 4, wherein the linear density of the streaks is 7500 (lines / mm) or more.
  6. The magnetic layer according to any one of claims 1 to 5, wherein the magnetic layer has a magnetic anisotropy index (retention force in the circumferential direction / retention force in the radial direction) of 1.05 or more. recoding media.
  7. The magnetic anisotropy index (remaining magnetization amount in the circumferential direction / remaining magnetization amount in the radial direction) of the residual magnetization amount is 1.05 or more, and is set to any one of claims 1 to 6. The magnetic recording medium according to the above.
  8. The non-magnetic underlayer comprises a Cr layer or a Cr alloy layer containing at least one selected from Ti, Mo, Al, Ta, W, Ni, B, Si and V. The magnetic recording medium according to any one of claims 1 to 7.
  9. The magnetic layer is made of a Co-Cr-Pt alloy, a Co-Cr-Pt-Ta alloy, a Co-Cr-Pt-B alloy, or a Co-Cr-Pt-BY alloy (Y is Ta or The magnetic recording medium according to any one of claims 1 to 8, comprising at least one selected from Cu).
  10. A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to claim 1; and a magnetic head for recording / reproducing information on / from the magnetic recording medium.
JP2002242518A 2002-08-22 2002-08-22 Magnetic recording medium, its manufacturing method and magnetic recording and reproducing device Pending JP2004086936A (en)

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SG200304489A SG123562A1 (en) 2002-08-22 2003-08-21 Method and system for validating detected rates ofreceived variable rate speech frames
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JP2005317181A (en) * 2004-03-31 2005-11-10 Hoya Corp Glass substrate for magnetic disk and magnetic disk
WO2006019063A1 (en) * 2004-08-16 2006-02-23 Showa Denko K.K. Magnetic recording medium and magnetic recording and reproducing device
WO2006095842A1 (en) * 2005-03-07 2006-09-14 Showa Denko K.K. Magnetic recording medium, production process thereof, and magnetic recording and reproducing apparatus
JP2007272995A (en) * 2006-03-31 2007-10-18 Hoya Corp Method for determining whether or not magnetic disk device and non-magnetic substrate are good, magnetic disk, and magnetic disk device
CN100414611C (en) * 2004-08-16 2008-08-27 昭和电工株式会社 Magnetic recording medium and magnetic recording and reproducing device
US7993497B2 (en) 2005-11-21 2011-08-09 Wd Media (Singapore) Pte. Ltd. Magnetic disk and magnetic disk manufacturing method

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KR0148842B1 (en) * 1993-07-22 1998-10-15 가나이 쯔또무 Magnetic recording medium, process for producing the same and magnetic recording system
US6582758B2 (en) * 2000-03-17 2003-06-24 Showa Denko Kabushiki Kaisha Process of producing a magnetic recording medium
US6821653B2 (en) * 2000-09-12 2004-11-23 Showa Denko Kabushiki Kaisha Magnetic recording medium, process for producing the same, and magnetic recording and reproducing apparatus
US6761982B2 (en) * 2000-12-28 2004-07-13 Showa Denko Kabushiki Kaisha Magnetic recording medium, production process and apparatus thereof, and magnetic recording and reproducing apparatus

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005317181A (en) * 2004-03-31 2005-11-10 Hoya Corp Glass substrate for magnetic disk and magnetic disk
WO2006019063A1 (en) * 2004-08-16 2006-02-23 Showa Denko K.K. Magnetic recording medium and magnetic recording and reproducing device
CN100414611C (en) * 2004-08-16 2008-08-27 昭和电工株式会社 Magnetic recording medium and magnetic recording and reproducing device
US7550211B2 (en) 2004-08-16 2009-06-23 Showa Denko K.K. Magnetic recording medium and magnetic recording and reproducing device
WO2006095842A1 (en) * 2005-03-07 2006-09-14 Showa Denko K.K. Magnetic recording medium, production process thereof, and magnetic recording and reproducing apparatus
US7993497B2 (en) 2005-11-21 2011-08-09 Wd Media (Singapore) Pte. Ltd. Magnetic disk and magnetic disk manufacturing method
JP2007272995A (en) * 2006-03-31 2007-10-18 Hoya Corp Method for determining whether or not magnetic disk device and non-magnetic substrate are good, magnetic disk, and magnetic disk device

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