JPH11175944A - Magnetic recording medium and magnetic storage device - Google Patents

Abstract

(57) [Problem] To provide a magnetic recording medium with low medium noise and capable of recording at an extremely high areal recording density excellent in electromagnetic conversion characteristics with high coercive force. An underlayer and a magnetic layer are provided on a substrate.
And the underlayer 12 and the magnetic layer 13 are both Co and C
The magnetic recording medium contains at least r, further has an underlayer 12 mainly having an amorphous structure, and has a region having a high oxygen concentration near the surface of the underlayer 12 on the side of the magnetic layer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic storage device used for an external storage device or the like of a computer system and a magnetic recording medium used therefor, and more particularly to a magnetic storage device having a magnetic recording medium compatible with a high recording density and a magnetic storage device having the same. The present invention relates to a magnetic recording medium to be used.

[0002]

2. Description of the Related Art In recent years, as the amount of information has increased, the tendency of magnetic storage devices to have higher densities, larger capacities, higher speed access, and smaller sizes has been increasing year by year. Accordingly, the diameter of the magnetic recording medium has been reduced, and the surface recording density has been steadily increasing. Further, the relative speed between the magnetic recording medium and the magnetic head has been reduced, and the conventional inductive type for recording and reproducing has been used. With magnetic heads, sufficient reproduction output and S / N cannot be secured.
Therefore, as a magnetic head for recording and reproducing information,
For example, a magneto-resistive magnetic head (MR head) has been used which can obtain a high reproduction output without depending on the relative speed between the magnetic recording medium and the magnetic head. In this magnetic head, a reproducing element and a recording element are independently formed, an MR head having a magnetoresistance effect (MR effect) as a reproducing element, a coil for changing magnetic flux as a recording element, and a coil for collecting the magnetic flux. It is often used as a composite magnetic head composed of an induction type thin film head having a pair of magnetic cores.

This MR head detects a physical phenomenon in which the electric resistance of a magnetoresistive layer from a recording medium changes according to the direction of magnetization as a change in the resistance, and converts a magnetic signal on the magnetic recording medium into an electric signal. It converts and reproduces information. Since the reproduction output of the MR head does not depend on the relative speed between the magnetic recording medium and the magnetic head, it is suitable for efficiently reproducing a signal recorded at high density on a small-diameter magnetic recording medium.

As an MR head for reproducing information utilizing such an MR effect, a conventionally known magnetic head having a small magnetoresistance is determined by an angle formed between a magnetization direction of a single magnetic film (single-layer film) and a current direction. Anisotropic magnetoresistance (AM
R) An AMR head using the effect has been commercialized, and at least two layers of magnetic films (multilayer film) for realizing magnetic recording with a high recording density of 3 gigabits per square inch or more, which are being commercialized recently. Using giant magnetoresistance change (GMR) caused by an angle change of the magnetization direction of
Development of an MR head is underway.

The MR head for reproducing information by utilizing the MR effect has an extremely high reproduction sensitivity and is suitable for high-density magnetic recording. However, since the sensitivity to noise as well as the reproduction signal from the magnetic recording medium also increases, the magnetic recording medium is required to have lower noise than ever.

On the other hand, a thin film magnetic recording medium in which a thin film of a metallic magnetic material is formed on a substrate by sputtering is used as the magnetic recording medium, but is suitable for high-density recording in order to cope with the above magnetic head. It is essential to develop a magnetic recording medium with high coercive force and low noise. In order to maintain the performance of the magnetic storage device within a certain range in various environments, it is necessary to reduce the rate of change of the coercive force with respect to the ambient temperature. Also, in order to reduce the noise of the magnetic recording medium, the crystal grains of the magnetic recording medium are made small and the particle diameters are made uniform.
Further, it is important to reduce the magnetic interaction between the crystal grains.

[0007] In the magnetic recording medium currently put into practical use,
Co-Cr-Pt, Co-Cr as the material of the recording magnetic layer
-Cot such as Pt-Ta, Co-Cr-Pt-B, etc.
An alloy layer having a high saturation magnetic flux density Bs and a high coercive force Hc is used. These Co alloy layers have a dense hexagonal filling structure (hcp structure) with the c-axis direction as the easy axis of magnetization. A crystal orientation in which the c-axis is oriented in the film plane is desirable for an in-plane magnetic recording medium.

[0008] However, such an orientation can be achieved by direct formation of C on the substrate.
O does not easily occur even if formed. Therefore, EUROPIAN
PATENT APPLICATION (European Patent) 0
As described in JP-A-140513, both the underlayer and the magnetic layer of the magnetic recording medium having the underlayer and the magnetic layer provided on the substrate have the same structure.
contains at least one element in addition to o and Cr, and
There has been proposed an in-plane magnetic recording medium in which the crystal lattice plane of Cr having a body-centered cubic structure (bcc structure) as a base layer has good matching with Co.

Further, as a prior art for increasing the coercive force, Japanese Patent Application Laid-Open No. Hei 4-15910 discloses that Ti, Z
r, Hf, V, Nb, Ta, Cr, Mo, W and Y
It has been shown that Hc can be improved by forming an amorphous or microcrystalline intermediate layer made of and then forming a metal underlayer and a magnetic layer thereon.

Japanese Patent Application Laid-Open No. 5-135343 discloses that a rare earth element, Ta, Y, Nb, Hf
It is shown that Hc can be improved by forming an oxygen-isolating intermediate layer containing at least one element selected from the group consisting of a metal underlayer and a magnetic layer thereon.

On the other hand, it is known that increasing the Cr concentration in the magnetic layer to reduce the magnetic interaction between the magnetic crystal grains is effective in reducing the medium noise. This is because the unit of magnetization reversal becomes smaller, the change in magnetization can be recorded more steeply in the transition region of magnetization, the noise at the time of reproduction is small, and a high S / N can be obtained. For this purpose, the minimum unit of the magnetization reversal needs to be as small as possible. However, if the minimum unit of the magnetization is excessively reduced, there is a problem that the coercive force Hc decreases. The minimum unit of the magnetization reversal can be evaluated by the product (vIs) of the activation volume v and the saturation magnetization Is.

In order to further reduce noise, Japanese Patent Laid-Open Publication No. 8-77543 discloses a technique in which crystal grains of a magnetic recording medium are made smaller to increase the fluctuation field (Hf) at a magnetic field strength equal to the remanent coercive force or coercive force. It is proposed in the gazette.

As a prior art for lowering the noise of a medium, Japanese Patent Application Laid-Open No. 7-57238 discloses that a thickness of 5 to 80 angstroms (Å) and a thickness of Cr (11
0) Cr-containing intermediate layer mainly composed of orientation (additive: O,
C, N, B, Ti, Mo, Zr, Hf, Si, Nb, A
It is shown that medium noise can be reduced by forming a base layer and a magnetic layer thereon after forming l, Y, V, Mn, Ag, and Gd).

Further, Japanese Patent Application Laid-Open No. 62-293511 discloses that a metal containing at least one element such as Ti, Zr, Ta or the like is deposited on a nonmagnetic substrate in order to improve the adhesiveness of a metal underlayer. A magnetic recording medium is disclosed in which an intermediate layer made of an oxide and whose oxygen concentration in a thickness direction decreases in the direction of a metal underlayer is formed, and a metal underlayer and a magnetic layer are formed thereon.

[0015]

The above-mentioned European Patent 0140
In the prior art described in Japanese Patent No. 513, it is possible to completely orient the easy axis of magnetization in the film plane, but there is a limit in maintaining epitaxial growth and at the same time miniaturizing crystal grains. Therefore, there is a problem that the electromagnetic conversion characteristics cannot be sufficiently obtained at a high linear recording density.

The prior art described in the above-mentioned JP-A-4-15910 and JP-A-5-135343 is disclosed in
When a magnetic recording medium manufactured using this method is combined with an MR head to produce a magnetic storage device having a high recording density of 2 gigabits or more, a medium using a glass substrate has a large medium noise and a sufficient electromagnetic wave. There is a problem that conversion characteristics (S / N) cannot be obtained.

In order to maintain the performance of the magnetic storage device within a certain range in various environments, it is necessary to reduce the rate of change of the coercive force of the magnetic recording medium with respect to the ambient temperature.
The prior art described in Japanese Patent Application Laid-Open No. 8-77543 is
Although noise during reproduction is small and a high S / N is exhibited, there is a problem that the temperature change rate of the coercive force increases and the performance of the magnetic storage device changes with temperature. When the medium noise is reduced by increasing Hf in this manner, the temperature change rate of the coercive force tends to increase. This is because, in a magnetic recording medium having a large Hf, the frequency of reversal of magnetization by an external magnetic field strongly depends on the ambient temperature.

In the prior art described in the above-mentioned Japanese Patent Application Laid-Open No. 7-57238, the film thickness must be controlled at a thinness of 5 to 80 angstroms (Å). There was a problem that control was difficult. Desirably, the thickness of each layer is at least 100 angstroms (Å) or more.

Further, the prior art described in Japanese Patent Application Laid-Open No. 62-293511 can improve the adhesiveness of the metal underlayer, but has a problem in that the effect of reducing the medium noise is not recognized.

An object of the present invention is to provide a magnetic recording medium which has a low medium noise and which can record at an extremely high areal recording density and has excellent coercive force and electromagnetic conversion characteristics.
Still another object of the present invention is to provide an inexpensive, small-sized, large-capacity, and reliable magnetic storage device using a magnetic recording medium having an extremely high areal recording density.

[0021]

In order to achieve the above object, a magnetic recording medium according to the present invention comprises an underlayer and a magnetic layer laminated on a substrate, and both the underlayer and the magnetic layer contain Co and Cr. At least, the underlayer mainly has an amorphous structure, and a region having a high oxygen concentration is provided near the surface of the underlayer on the magnetic layer side.

The underlayer preferably contains at least one element selected from Zr and Ta. Zr and T
a is 4 at. % Is preferable.
4 at. If the content is less than 10%, it is difficult to form an amorphous structure. The upper limit of the amount is such that the total amount of Zr, Ta and Cr is 50 at. % Is preferred.
The underlayer may have a structure in which the oxygen concentration is higher near the surface on the magnetic layer side than at the center in the thickness direction. Further, the magnetic recording medium preferably has a coercive force measured in the circumferential direction of 120 kA / m or more.

According to another aspect of the present invention, there is provided a magnetic storage device comprising: a magnetic recording medium; a driving unit for driving the magnetic recording medium in a recording direction; a magnetic head including a recording unit and a reproducing unit. Means for moving the magnetic head relative to the magnetic recording medium, and recording / reproducing signal processing means for obtaining a recording signal input to the magnetic head and a reproducing signal output from the magnetic head. A base layer and a magnetic layer are laminated on a substrate, the base layer and the magnetic layer both contain at least Co and Cr, the base layer has a mainly amorphous structure, and the base layer has a magnetic layer. A region having a high oxygen concentration is provided near the surface on the side.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described in detail with reference to the drawings. <Embodiment 1> FIG. 4 is a perspective view showing a magnetic storage device according to an embodiment of the present invention. The magnetic storage device includes a magnetic recording medium 203, a spindle motor 202 as a driving unit for driving the magnetic recording medium 203 in a recording direction, a magnetic head 204 including a recording unit and a reproducing unit, and the magnetic head 204 mounted on the magnetic recording medium 203. It has a guide arm 205 as means for making relative movement with respect to it, and a recording / reproducing signal processing circuit 201 for reproducing a signal input to the magnetic head 204 and reproducing an output signal from the magnetic head 204. Note that an actual magnetic storage device has a plurality of magnetic recording media 203 and a plurality of guide arms 205 and a plurality of magnetic heads 204 corresponding to each magnetic recording medium 203. The magnetic head 204 constituting the magnetic storage device according to the present invention is not only an MR head using the anisotropic magnetoresistance effect (AMR), but also a spin valve type MR head using the giant magnetoresistance effect (GMR). Applicable.

<Embodiment 2> FIG. 1 is a schematic sectional view showing the layer structure of a magnetic recording medium according to this embodiment. The substrate 11 has a diameter of 2.
5 inch 0.635 mm thick chemically strengthened soda lime glass was used. After the substrate was washed, a thin film was continuously formed using a stationary facing type sputtering apparatus. First, the substrate is evacuated to vacuum and without preheating, Co-35a
t. % Cr-5 at. % Mo-5 at. An underlayer 12 having a thickness of 25 nm and made of a% Zr alloy was formed at an Ar gas pressure of 2.7 Pa. After the formation of the underlayer, 10 vol. Substrate temperature in low vacuum with 2% addition
The substrate was heated to a temperature of 00 ° C. Further, under a vacuum containing no oxygen, a magnetic layer 13 made of a Co—Cr—Pt alloy was formed to a thickness of 20 nm, and then a carbon protective film 14 having a thickness of 10 nm was formed by DC sputtering. After film formation,
The surface protrusions were mechanically removed so that low flying was guaranteed, and a material obtained by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material was applied as a lubricating film 15.

A sample piece was cut out from the above magnetic recording medium so that the vertical and horizontal lengths became 8 mm each, and the coercive force at room temperature was measured with a sample vibration magnetometer. As a result, the coercive force measured in the circumferential direction by a plurality of measurement results was 120 kA / m or more. Further, as a result of measuring the X-ray diffraction, no diffraction peak was obtained other than the diffraction peak obtained from the magnetic layer. The element distribution in the depth direction was measured by Auger electron spectroscopy. As a result, it was found that the oxygen concentration was high at the interface between the Co—Cr—Mo—Zr alloy underlayer and the magnetic layer.

The magnetic layer is made of Co-C instead of the above material.
r-Pt, Co-Cr- Pt-SiO 2, Co-Cr-
Pt-Ta, Co-Cr-V-Pt, Co-Cr-Pt
-Ti, Co-Cr-Ta, Co-Ni-Cr, Co-
Although an alloy containing Co as a main component such as Cr-Pt-Mn can be used, it is particularly preferable to use a Co alloy containing Pt in order to obtain a high coercive force. Also, Sm-C
o, a magnetic alloy containing a rare earth element such as Fe-Sm-N can also be used. Further, the magnetic layer may be composed of a plurality of magnetic layers directly or via a non-magnetic intermediate layer.

Further, as a protective layer, a carbon film to which hydrogen is added, silicon carbide, tungsten carbide, (W-Mo)
It is preferable to use a film made of a compound such as —C, (Zr—Nb) —N, or a mixed film or a laminated film of these compounds and carbon, because the sliding resistance and the corrosion resistance can be improved. Also, after forming these protective layers, plasma etching using a fine mask or the like to form fine irregularities on the surface, or a compound, using a target of a mixture to cause projections on the protective layer surface, It is preferable to form irregularities on the surface by heat treatment because the contact area between the head and the medium can be reduced, and the problem of the head sticking to the medium surface during CSS operation is preferable.

COMPARATIVE EXAMPLE 1 A substrate temperature of 20 was formed in a low vacuum containing oxygen without forming an underlayer on the cleaned substrate.
The substrate was heated to 0 ° C. Further, without intentionally adding oxygen, the following was performed in the same manner as in Example 2 to obtain Ar
Using a gas, a Co—Cr—Pt alloy magnetic layer having a thickness of 20 nm was formed, and then a carbon protective film having a thickness of 10 nm was formed by a DC sputtering method. In this case, the coercive force measured in the circumferential direction did not exceed 120 kA / m. This is presumably because the surface state of the substrate was not stabilized even when the substrate was heated in a vacuum, and as a result, the crystal growth direction of the magnetic layer could not be controlled.

Example 3 Ni-P with 2.5 inch diameter
After washing the substrate on a plated 0.8 mm thick Al alloy substrate in the same manner as in Example 2, a thin film was continuously formed using a stationary facing type sputtering apparatus. First, the substrate was evacuated to a vacuum and without preheating, Co-37 at. % C
r-5 at. % Ta-5 at. An underlayer 12 made of a% Zr alloy and having a thickness of 30 nm was formed. After that, 10vo
l. Substrate temperature is 200 ° C in a low vacuum with oxygen
The substrate was heated so that Further Co-17a
t. % Cr-8 at. % Pt-4 mol. % Of SiO ₂ alloy magnetic layer 13 22 nm, then the thickness of 9nm carbon protective film 14 was formed by DC sputtering. After the formation of the protective film, the surface protrusions are mechanically removed so that low flying is guaranteed, and a material obtained by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material is used as a lubricant film 1.
5 was applied.

A sample piece was cut out from the above-mentioned magnetic recording medium so that each of the vertical and horizontal lengths became 8 mm, and the coercive force was measured with a sample vibration magnetometer. As a result, the coercive force measured in the circumferential direction was 120 kA /
m or more. Further, as a result of measuring the X-ray diffraction, no diffraction peak was obtained other than the diffraction peak obtained from the magnetic layer. The element distribution in the depth direction was measured by Auger electron spectroscopy. As a result, it was found that the interface between the underlayer and the magnetic layer had a high oxygen concentration.

The magnetic recording medium was incorporated in a magnetic storage device that rotates at a high speed of 10,000 rpm or more. As a result, it was clarified that the magnetic recording medium was less deformed in spite of the high-speed rotation as compared with the case where a conventionally formed magnetic recording medium having a thickness of 0.635 mm was incorporated.

Example 4 The composition of the target used to form the underlayer in Example 2 was Co-42 at. % C
r-10 at. An underlayer was formed instead of the% Ta alloy.
The formation of the underlayer was performed by heating. Then 10
vol. 200 ° C. in a low vacuum with the addition of
The substrate was heated. A magnetic recording medium was experimentally manufactured under the same conditions as in Example 2 except for the above.

Samples were cut out from these magnetic recording media so that the vertical and horizontal lengths became 8 mm each, and the coercive force at 24 ° C. and the activation magnetic moment vIs were measured with a sample vibration type magnetometer. As a result, the coercive force measured in the circumferential direction of all the samples became 120 kA / m or more, but when the X-ray diffraction was measured on a magnetic recording medium heated to 250 ° C. or more, it was obtained from the magnetic layer. It became clear that the 00 · 2 diffraction intensity was the highest among the diffraction peaks. From these results, it is evident that considering the in-plane magnetization component, it is preferable to lower the substrate temperature during formation of the underlayer because the 0. 02 diffraction intensity does not become the strongest among the X-ray diffraction peaks. Was.

On the other hand, as a result of measuring the activation magnetic moment vIs, vIs increases as the substrate temperature decreases. To realize high-density magnetic recording, if the substrate temperature is too low, noise increases, which is not preferable. It became clear. It is considered that the reason why vIs increased with the decrease in the substrate temperature was that the fluctuation of the Cr concentration in the magnetic layer was reduced due to the decrease in the substrate temperature. From these conflicting results, it is considered that the substrate temperature is preferably set to approximately 100 to 200 ° C. This optimum substrate temperature depends on the composition of the amorphous alloy used for the underlayer. This is because the crystallization temperature of the amorphous alloy depends on the composition, and the activity for oxygen is different.

Example 5 Co-35 at. % Cr-5
at. % Mo-5 at. 25n thickness made of% Zr alloy
m, an underlayer 12 of 2.0, 1.4, 0.7, 0.3 Pa
Except that it was formed so as to have an Ar gas pressure of
A magnetic recording medium was formed in the same manner as in Example 2.

A sample piece was cut out from this magnetic recording medium so that each of the vertical and horizontal lengths became 8 mm, and the coercive force at room temperature was measured with a sample vibration magnetometer. As a result, when the underlayer was formed at 0.7 Pa and 0.3 Pa, the coercive force measured in the circumferential direction by a plurality of measurement results included 120 kA /
m. This is presumably because the surface shape of the underlayer is made smooth by lowering the discharge gas pressure when the underlayer is formed, and the crystal growth direction of the film epitaxially grown thereon is different from that in the second embodiment. The formation of the underlayer is preferably performed at a gas pressure in the range of 1.0 Pa to 3.0 Pa.

<Embodiment 6> FIG. 1 is a schematic sectional view showing the layer structure of a magnetic recording medium according to this embodiment. The substrate 11 has a diameter of 2.
5 inch 0.635 mm thick chemically strengthened soda lime glass was used. After the substrate was washed, a thin film was continuously formed using a stationary facing type sputtering apparatus. First, the substrate is evacuated to vacuum and without preheating, Co-30a
t. % Cr-5 at. 25nm thick made of% Zr alloy
Was formed so that the Ar gas pressure was 2.7 Pa. Thereafter, the substrate was heated so that the substrate temperature became 270 ° C., and the substrate was exposed to Ar gas containing 1 mol% oxygen at 0.6 Pa for 3.5 seconds. Further, the Co-Cr-6% Pt alloy magnetic layer 13 is
0 nm and then an 8 nm thick carbon protective film 14
It was formed by a sputtering method. After the formation of the film, surface protrusions were mechanically removed to ensure low flying, and a lubricating film 15 was applied by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material.

A sample piece was cut out from the above-mentioned magnetic recording medium so that the vertical and horizontal lengths became 8 mm each, and the coercive force at room temperature was measured with a sample vibration type magnetometer. As a result, the coercive force measured in the circumferential direction by a plurality of measurement results was 120 kA / m or more. Further, as a result of measuring the X-ray diffraction, as in the case of Example 2, no diffraction peak was obtained other than the diffraction peak obtained from the magnetic layer. The element distribution in the depth direction was measured by Auger electron spectroscopy. As a result Co
It was found that the oxygen concentration was high at the interface between the -Cr-Mo-Zr alloy underlayer and the magnetic layer.

Comparative Example 2 In the same manner as in Example 6, after cleaning the substrate, a thin film was continuously formed using a stationary facing type sputtering apparatus. First, the substrate was evacuated to a vacuum and without preheating, Co-30 at. % Cr-5 at. % Zr alloy with a thickness of 25 Pa
It was formed so as to have an r gas pressure. Thereafter, the substrate is heated so that the substrate temperature becomes 270 ° C., and without being exposed to Ar gas containing 1 mol% oxygen, Co-
A Cr-6% Pt alloy magnetic layer 13 is formed directly on the heated substrate to have a thickness of 50 nm, and then has a thickness of 8 n.
m of the carbon protective film 14 was formed by DC sputtering. After the formation of the film, surface protrusions were mechanically removed so that low flying was guaranteed, and a material obtained by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material was applied as a lubricant 15.

FIG. 3 shows the result of X-ray diffraction measurement of a sample piece cut out from the above-mentioned magnetic recording medium so that each of the vertical and horizontal lengths was 8 mm. As is apparent from these results, when the Co—Cr—Pt magnetic layer was continuously formed on the underlayer without being exposed to Ar gas containing 1 mol% oxygen, the hcp structure of 00 · 2 Strong diffraction intensity, h
The 10.0 diffraction intensity of the cp structure was at the noise level.
On the other hand, in the case of Example 6 which was exposed to Ar gas containing 1 mol% oxygen at 0.6 Pa for 3.5 seconds, the 00 · 2 diffraction intensity of the hcp structure decreased as compared with the case of Comparative Example 2. , H
The 10.0 diffraction intensity of the cp structure was relatively increased.
This measurement result supports that the in-plane component of the magnetization is increasing.

Example 7 A magnetic recording medium was manufactured under the same conditions as in Example 4 except that the substrate temperature immediately before forming the underlayer was fixed at 100 ° C. and the substrate temperature was changed immediately before forming the magnetic film. Was prototyped. As in the case of Example 4, a sample piece was cut out from each of these magnetic recording media so that the length and width were each 8 mm, and the coercive force and the activation magnetic moment vIs at 24 ° C. were measured using a sample vibrating magnetometer. Was measured.
As a result, the coercive force measured in the circumferential direction was 1 for all samples.
It was 20 kA / m or more. The activation magnetic moment vIs decreased as the substrate temperature increased. In order to realize high-density magnetic recording, it is not preferable that the substrate temperature immediately before forming the magnetic layer is too low, because noise increases. When X-ray diffraction was measured on a magnetic recording medium heated to 250 ° C. or higher, the 00 · 2 diffraction intensity did not become the highest among the diffraction peaks obtained from the magnetic layer. From these results, the substrate temperature immediately before forming the magnetic layer is approximately 200 ° C. or higher, more preferably, approximately 300 ° C., and 380 ° C.
It is considered good to set the following. The optimum substrate temperature depends on the composition of the amorphous alloy used for the underlayer, the thin film forming apparatus and the process, and the like. The optimum substrate temperature depends on the composition of the amorphous alloy used for the underlayer because the crystallization temperature of the amorphous alloy depends on the composition and the activity with respect to oxygen is different. It is a well-known fact that the above optimum substrate temperature depends on the process and the process.

In the magnetic recording medium of the present invention, in order to facilitate nucleation of the magnetic layer and to form many nuclei, a region having a high oxygen concentration is provided at the interface between the underlayer and the magnetic layer (near the surface of the underlayer). Have. Here, the oxygen concentration may be added to such an extent that the additional elements other than Co contained in the underlayer are oxidized, and the oxygen concentration is good enough that Co contained in the underlayer is not significantly oxidized.

When the coercive force of the magnetic recording medium measured by applying a magnetic field in the circumferential direction of the magnetic recording medium is set to 120 kA / m or more, sufficient signal intensity at a high recording density can be obtained, and isolated reproduction can be performed. The output resolution for the output of the wave can be increased. By using a magnetic recording medium whose base layer mainly has an amorphous structure, a low-noise magnetic recording medium for a magnetic storage device having a recording density of 2 gigabits per square inch or more can be realized.

The substrate is not limited to a thickness of 0.635 mm in the case of a diameter of 2.5 inches, but is not limited to a thickness of 0.51 mm in the case of a glass magnetic recording medium considering high-density mounting.
The following substrates can be used. Also, 10,0
To realize high-speed rotation exceeding 00 rpm, Ni-
It is also possible to use a P-plated Al alloy having a thickness of about 0.8 mm as the substrate.

The material used for the underlayer is Co-35 at.
% Cr-5 at. % Mo-5 at. % Zr, Co-37
at. % Cr-5 at. % Ta-5 at. % Zr, Co
-40 at. % Cr-8 at. % Mo-5at% Ta-
10 at. % Zr, Co-42 at. % Cr-10a
t. % Ta alloy or the like containing at least Co and Cr and having a mainly amorphous structure is preferable since the surface can be oxidized. 35a Cr to Co
t. % To 40 at. The addition of% is for eliminating the magnetization of Co. At least one selected from Zr and Ta
The reason why these elements are included is that a metal-metal based amorphous film can be formed by adding these elements. Although it is possible to form an underlayer of an amorphous film by adding a semimetal such as Si, B, P, etc., the underlayer of an amorphous film formed by adding these elements easily rusts, Even after the substrate is washed with water, the remaining water cannot be removed even by vacuum heating, which may cause a change with time, and there is a problem in the corrosion resistance. For this reason, the underlayer is made of Zr, Ta as described above.
A metal containing at least one element selected from
It is preferably a metal-based amorphous film.

The thickness of the underlayer is preferably in the range of 10 to 50 nm, more preferably in the range of 15 to 30 nm. Since the underlying layer has a significantly amorphous structure, an adhesive layer 21 of Cr or the like is formed between the substrate and the underlying layer 12 as shown in FIG. Even if it does not affect the effect of the present invention.

If the underlayer is formed by a usual high-frequency sputtering method, the substrate surface temperature easily rises and the underlayer is easily crystallized. Therefore, it is desirable to form the underlayer by magnetron sputtering. Further, from the viewpoint of reducing the medium noise, it is desirable to increase the discharge gas pressure when forming the underlayer, and at the same time, lower the substrate temperature to promote the spatial separation of the underlayer surface by the self-shading effect of sputtered particles. . After oxidizing the surface of the amorphous underlayer formed in this manner, a Co-based magnetic film is formed, and a Co-based magnetic film is formed.
The dispersion of the c-axis, which is the axis of easy magnetization of the alloy, in the direction normal to the film surface is represented by ω
Measured at -scan. As the X-ray source, a characteristic X-ray (Kα ray) of copper via a Ni foil was used. The divergence slit and the scattering prevention slit are each 0.5 degrees, and the light receiving slit is 0.15.
mm. The scanning speed was 2 degrees / minute. As a result, 0
It was found that the half width of the 02 reflection intensity was 30 degrees or more, the in-plane component of magnetization was considerably large, and the in-plane component of the easy axis was large.

The magnetic layer is made of Co-Cr-Pt, Co-Cr
-Pt-Ta, Co-Cr-Pt-B, Co-Cr-P
t-V, Co-Cr-Pt-Mn, Co-Cr-Pt-
An alloy containing Co as a main component and containing Pt, such as a Ta-Nb alloy, is preferable because the coercive force can be increased. Oxide and Ni
Co- containing an alloy containing no Cr as a magnetic layer
The coercive force measured in the in-plane direction of the film on the amorphous underlayer could be improved even with the Ni-Pt-Si-O system. However, the activation magnetic moment related to the magnetization reversal unit is 1.2 fe.
It was necessary to increase the amount of silicon oxide to be added in order to make mu (femto emu) or less. As a result, the residual magnetic flux density was reduced, and when silicon oxide was added, the output resolution was greatly reduced at a high linear recording density. From these examination results, an alloy containing Co as a main component and containing at least Cr and Pt is preferable as an alloy constituting the magnetic layer. Cr concentration is 18 at. % Or more, 25 at. % Is preferable because the medium noise is further reduced.

Further, it is preferable that carbon is formed to a thickness of 5 nm to 30 nm as a protective layer of the magnetic layer, and a lubricating layer of an adsorbing perfluoroalkyl polyether or the like is further provided to a thickness of 2 nm to 10 nm. A magnetic recording medium capable of high-density recording of 2 gigabits or more per square inch can be obtained.

[0051]

According to the magnetic recording medium of the present invention, the medium S
/ N can be increased, so that medium noise can be sufficiently reduced, and sufficient signal strength at a high recording density can be obtained by increasing the coercive force.
The output resolution with respect to the output of the isolated reproduction wave can be increased, and recording can be performed at an extremely high areal recording density.

Further, by combining this magnetic recording medium with an MR head, a technique for positioning the magnetic head with high accuracy, and the like, an inexpensive, compact, large-capacity, highly reliable magnetic storage having an extremely high areal recording density. A device is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a layer configuration of a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a layer configuration of a magnetic recording medium according to another embodiment of the present invention.

FIG. 3 is a graph showing the results of X-ray diffraction measurement of magnetic recording medium samples according to an example of the present invention and a comparative example.

FIG. 4 is a perspective view showing a magnetic storage device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Substrate 12 ... Underlayer 13 ... Magnetic layer 14 ... Protective film 15 ... Lubricating film 21 ... Adhesive layer 201 ... Recording / reproducing signal processing circuit 202 ... Spindle motor 203 ... Magnetic recording medium 204 ... Magnetic head 205 ... Guide arm

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshifumi Matsuda 2880 Kozu, Odawara-shi, Kanagawa Prefecture Within the Hitachi, Ltd. Storage Systems Division (72) Inventor Yoshio Yaku 2880 Kozu, Kozu, Odawara-shi, Kanagawa Hitachi, Ltd. Within the Storage System Division (72) Koji Sakamoto 2880 Kozu, Odawara City, Kanagawa Prefecture Within the Storage Systems Division Hitachi, Ltd. (72) Toshio Hishinuma 2880 Kozu, Kozu, Odawara City, Kanagawa Prefecture Storage System Division, Hitachi, Ltd.

Claims (3)

[Claims] 1. A magnetic recording medium comprising a substrate, an underlayer disposed on the substrate, and a magnetic layer disposed on the underlayer, wherein the underlayer and the magnetic layer both contain at least Co and Cr. A magnetic recording medium, wherein the underlayer has a mainly amorphous structure, and a region having a high oxygen concentration is provided near the surface of the underlayer on the side of the magnetic layer. 2. The magnetic recording medium according to claim 1, wherein the underlayer has at least one element selected from the group consisting of Zr and Ta. 3. A magnetic recording medium, a driving unit for driving the magnetic recording medium in a recording direction, a magnetic head including a recording unit and a reproducing unit, and means for moving the magnetic head relative to the magnetic recording medium. 3. The magnetic storage device according to claim 1, wherein the magnetic recording medium includes: a recording signal input unit for obtaining a recording signal input to the magnetic head and a reproduction signal output from the magnetic head. A magnetic storage device, which is a recording medium.