JPH0822615A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having characteristics suitable for a fixed magnetic disk device using an MR head. CONSTITUTION:A nonmagnetic metallic underlayer 2, a magnetic layer 3, a protective film 4 and a lubricative film 5 are successively formed on a nonmagnetic substrate 1 to obtain the objective magnetic recording medium having <=7,000Gauss saturation magnetic flux density Bs. The magnetic layer 3 is formed with a Co alloy contg. at least 10-16at.% Cr, 3-6at.% Ta and <=4at.% Pi.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used in a fixed magnetic disk device or the like, and more specifically in MR.
The present invention relates to a magnetic recording medium suitable for a head.

[0002]

2. Description of the Related Art External information processing devices such as computers
The fixed magnetic disk device used as a storage device,
Conventionally, information is recorded / reproduced using the electromagnetic induction phenomenon.
Inductive magnetic heads have been used. this
Fixed magnetic disk using inductive magnetic head
The magnetic characteristics of the magnetic recording medium installed in the device are
In addition to having a large Hc, the residual magnetic flux density Br and the magnetic layer film
The product Br · δ with the thickness δ is required to be large. this
Increase the leakage flux generated from the magnetic recording medium.
And the reproducing voltage induced in the magnetic head by electromagnetic induction.
Is necessary to improve the reproduction characteristics. This
In order to meet these requirements, the magnetic layer material must be a coercive
The force Hc is as large as 2000 Oe or more and the saturation magnetic flux density is high.
Relatively large material with degree Bs of about 7500 Gauss or more
Fee, eg Co₈₆Cr₁₂Ta₂And Co _62.5Ni₃₀Cr
_7.5Have been commonly used.

Recently, an MR system head using the magnetoresistive effect (MR effect) for reproducing information has been developed. Instead of the inductive magnetic head, the information recording is performed by the inductive system head and the information is reproduced. A fixed magnetic disk device using the MR head, which is performed by the MR head, has been put to practical use. Since the MR type head has a very good sensitivity to magnetic flux, it does not require a large Br · δ, which has been required in the magnetic recording medium to improve the information reproducing characteristics, and, conversely, a strong magnetic field. When exposed, a problem arises in that the MR system head itself is damaged, so Br.delta. Of the magnetic recording medium must be reduced. Specifically, the magnetic recording medium for an inductive magnetic head has a Br · δ of 250 Gaus.
s · μm to 450 Gauss · μm, but M
Br · δ of the magnetic recording medium for the R head is 100 Gaus
s · μm to 200 Gauss · μm, and even lower.

Conventionally, such a magnetic recording medium for an MR head uses the same magnetic material as the magnetic recording medium for a conventional inductive magnetic head, and Br.delta. Is reduced by thinning the thickness of the magnetic layer. Was manufactured by the method.

[0005]

However, in the conventional technique in which the thickness of the magnetic layer is reduced to reduce Br · δ, the thickness of the magnetic layer is extremely reduced, and thus the steepness of the magnetization reaction is exhibited. There is a drawback that the coercive force squareness ratio S ^*, which is a parameter, becomes extremely small. Therefore, when information is recorded / reproduced using such a magnetic recording medium, D _50, which represents the linear recording density, is disadvantageous for high-density recording, and the full width at half maximum PW ₅₀ of the reproduced signal is also increased. There was a problem.

The present invention has been made in view of the above points, and has a large coercive force Hc and a small Br · δ,
In addition, it has magnetic characteristics with a large coercive force squareness ratio S ^* ,
An object of the present invention is to provide a magnetic recording medium suitable for a fixed magnetic disk device using a head.

[0007]

SUMMARY OF THE INVENTION The above-mentioned object is achieved by the present invention.
According to the non-magnetic substrate, a non-magnetic metal underlayer, a magnetic layer,
Magnetic recording medium in which a protective film and a lubricating layer are formed in this order
In the magnetic layer, the magnetic layer of 10 atomic% to 16 atomic%
Cr, 3 atomic% to 6 atomic% Ta and 4 atomic% or less
It is formed of a Co alloy containing at least Pt below and has a saturation magnetic flux.
Density Bs is 7,000 Gauss (0.70 Tesla)
It is solved by the following magnetic recording medium
It Among them, the coercive force Hc is 2000 Oe or more,
The product Br · δ of the flux density Br and the magnetic layer thickness δ is 100 Ga.
Uss / μm, coercive force squareness ratio S ^*Is 0.9 or more
A magnetic recording medium according to the present invention is suitable.

[0008]

A magnetic layer is formed using a CoCrTaPt-based alloy, and the saturation magnetic flux density Bs is 7,000 Gauss (0.70).
The magnetic recording medium having a magnetic coercive force Hc, a small Br · δ and a large coercive force squareness ratio S ^* is suitable for an MR head by using a magnetic recording medium having a magnetic field density of less than Tesla). Is obtained.

In the case of magnetic characteristics such that Bs exceeds 7,000 Gauss, Br * δ is made small so as to be suitable for an MR head, for example, when it is made as small as 100 Gauss ^* μm, the value of S ^* is 0.85 or less. Therefore, the recording / reproducing characteristics are deteriorated when the MR head is used. This is because when the Br · δ is reduced, the film thickness δ of the magnetic layer becomes 150 Å or less, and accordingly, the grain size of the crystal forming the magnetic layer becomes extremely small, 150 Å or less, and the magnetic mutual relation between the crystal grains becomes large. It is considered that the action is relatively greatly reduced.

Even when Bs is 7,000 Gauss or less, it is difficult to obtain a large Hc exceeding 2000 Oe when using, for example, a well-known CoCrTa-based material as a magnetic material, and S ^* Since the value also decreases, it is not suitable as a magnetic recording medium. On the other hand, when a CoNiCr-based material containing a large amount of Ni is used as the magnetic material, noise of the medium during reproduction remarkably increases, which is also unsuitable.

The composition of the above CoCrTaPt-based alloy is such that Cr is 10 atomic% or more and 16 atomic% or less and Ta is 3 or less.
It is desirable that the content of Pt be 4 atomic% or less and the content of Pt be 4 atomic% or less. When the content of Cr is less than 10 atomic%, the Hc value is lowered, which is not suitable, and when it exceeds 16 atomic%, Cr is segregated to a large amount at the crystal grain boundaries during the sputtering deposition of the magnetic layer, resulting in a crystal. Since it reduces the magnetic interaction between grains, S ^*
This is unsuitable because it causes a decrease in the value. Further, when the Ta content is less than 3 atomic%, it is difficult to reduce the Bs value to 7,000 Gauss or less in the Cr content range of 16 atomic% or less, and the Ta content exceeds 6 atomic% and is large. If this happens, the Hc value will decrease, which is unsuitable. Also, P
If t is not contained, it is difficult to obtain the required magnetic characteristics, and if the content exceeds 4 atomic%, the medium noise becomes large, and the cost becomes high by using a large amount of expensive Pt. So inappropriate.

[0012]

Embodiments of the present invention will be described below.
FIG. 3 schematically shows the structure of the magnetic recording medium according to the present invention. The non-magnetic metal underlayer 2, the magnetic layer 3, and the protective film 4 are sequentially sputtered on the non-magnetic substrate 1, and a liquid lubricant is applied thereon to form a lubricating layer 5.

Example 1 A disk-shaped Al alloy substrate plated with Ni-P electroless plating was pressed against a surface of a disk-shaped Al alloy substrate with white alumina having an average abrasive grain size of 2 μm by a rubber roller to rotate the substrate. The first texture processing is performed, and then the slurry containing white alumina having an average abrasive grain size of 1 μm is dropped onto the flocking tape pressed against the surface of the substrate by the rubber roller, and the substrate is rotated to perform the second texture processing. Use as a base. On this substrate, a non-magnetic metal underlayer having a thickness of 750 Å Cr underlayer and a magnetic layer of Co ₈₀ Cr ₁₄ Pt ₂ Ta ₄ were formed by a transfer type DC magnetron sputtering method in an Ar gas atmosphere at a pressure of 5 mTorr in a chamber. The alloy layer was continuously formed. On top of that, by a transfer type DC magnetron sputtering method, a mixed gas in which Ar is mixed with CH ₄ at a 30% molar concentration is flown in the chamber at a flow rate of 20 SCCM and the pressure is 5
Carbon was sputter-deposited in an atmosphere kept at mTorr to form a protective film having a film thickness of 150Å. A perfluoropolyether-based lubricant was applied on the carbon protective film to form a lubricating layer having a film thickness of 18Å to 22Å, and the magnetic recording medium having the structure shown in FIG. 3 was produced. The thickness of the magnetic layer is such that the medium Br · δ is about 100 Gauss · μm (G · μm).
So that

The magnetic characteristics and the recording / reproducing characteristics of the magnetic recording medium of Example 1 thus manufactured were evaluated.
The magnetic characteristics were measured with a sample vibrating magnetometer (VSM), and the recording / reproducing characteristics were measured under the conditions shown in Table 1. Table 2 shows the measurement results of the magnetic characteristics, and Table 3 shows the measurement results of the recording / reproducing characteristics. Table 2 also shows the composition of the magnetic layer of each magnetic recording medium.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

As can be seen from Tables 2 and 3, the medium of Example 1 has a coercive force Hc of 2200 Oe and a coercive force squareness ratio S ^* value of 0. 0 even when Br · δ is about 100 G · μm. 91
3 was good, and the recording / reproducing characteristics were also good. In the above-mentioned manufacturing method, the magnetic layer is sputter-deposited using a target having various alloy compositions as a sputtering target for forming the magnetic layer, and various magnetic recording media having different alloy compositions of the magnetic layer are produced. The relationship between magnetic properties and alloy composition was investigated. The alloy composition of the magnetic layer was measured by ICP emission spectroscopy. Figure 1 shows the relationship between coercive force Hc and alloy composition.
Further, FIG. 2 shows the relationship between the coercive force squareness ratio S ^* and the composition.
Regarding the alloy composition, the abscissa of each figure shows the amount of Cr in Co as a
The amount of Ta and the amount of Pt in Co are 2 at% Ta and 3 at% Pt, 4 as parameters.
at% Ta and 3 at% Pt, 7 at% Ta and 3
At% Pt, 4 at% Ta, and 5 at% Pt are changed in four ways.

From FIGS. 1 and 2, the Cr content is 10 at%.
It can be seen that a high S ^* is obtained together with a high Hc in the range of -16 at% and Ta amount within the range of 3 at% to 6 at%.
When the recording / reproducing characteristics were evaluated, high H
Good characteristics were obtained within the composition range in which c, S ^* was obtained and further containing 4 at% or less of Pt. It became large and good recording / reproducing characteristics could not be obtained.

Comparative Example 1 In Example 1, the alloy composition of the magnetic layer was changed to Co ₈₆ Cr ₁₂ T.
Other than changing the a ₂ is A magnetic recording medium was manufactured in the same manner as in Example 1 to evaluate the magnetic properties and the recording and reproducing characteristics. The results are shown in Tables 2 and 3 together with the medium of Example 1. As seen in Tables 2 and 3, the saturation magnetic flux density Bs is 7700 Gauss, and the coercive force squareness ratio S ^* is 0.8.
It is as low as 3, and the recording / playback characteristics are poor.

Comparative Example 2 In Example 1, the alloy composition of the magnetic layer was changed to Co ₈₂ Cr ₁₄ T 2.
Other than changing the a ₄ will produce a magnetic recording medium in the same manner as in Example 1 to evaluate the magnetic properties and the recording and reproducing characteristics. The results are also shown in Tables 2 and 3. As can be seen from Tables 2 and 3, the saturation magnetic flux density Bs is 6700 Gaus.
However, since it does not contain Pt, the coercive force Hc is low and therefore the recording / reproducing characteristics are also poor.

Comparative Example 3 In Example 1, the alloy composition of the magnetic layer was changed to Co ₅₉ Ni ₂₅ C.
A magnetic recording medium was produced in the same manner as in Example 1 except that the magnetic recording medium was changed to r ₁₂ Ta _4, and the magnetic characteristics and the recording / reproducing characteristics were evaluated. The results are also shown in Tables 2 and 3. Table 2,
As shown in Table 3, the saturation magnetic flux density Bs is 6800G.
However, as shown in Table 3, noise during recording / reproduction is large, which is not preferable.

[0023]

According to the present invention, in a magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic layer, a protective film, and a lubricating layer are formed in this order on a nonmagnetic substrate, the magnetic layer is 10 atomic% or more. 16 atom% Cr and 3 atom% to 6 atom%
Of Co and at least 4 atomic% of Pt and having a saturation magnetic flux density Bs of 7,000 Gauss
The magnetic recording medium is (0.70 Tesla) or less. Such a magnetic recording medium has a Br · δ of 100 G ·
Even when it is as small as about μm, a high coercive force Hc and a high coercive force squareness ratio S ^* which could not be obtained in the past can be realized at the same time, and it is particularly suitable for a fixed magnetic disk device using an MR head.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a coercive force Hc of a magnetic recording medium according to the present invention and an alloy composition of a magnetic layer.

FIG. 2 is a diagram showing the relationship between the coercive force squareness ratio S ^{* of the} magnetic recording medium according to the present invention and the alloy composition of the magnetic layer.

FIG. 3 is a schematic sectional view of a magnetic recording medium according to the present invention.

[Explanation of symbols]

 1 Nonmagnetic Substrate 2 Nonmagnetic Metal Underlayer 3 Magnetic Layer 4 Protective Film 5 Lubrication Layer

Claims (2)

[Claims] 1. A magnetic recording medium comprising a non-magnetic metal underlayer, a magnetic layer, a protective film and a lubricating layer formed in this order on a non-magnetic substrate, wherein the magnetic layer comprises 10 atomic% to 16 atomic% of Cr, It is made of a Co alloy containing at least 3 atomic% to 6 atomic% Ta and 4 atomic% or less Pt, and has a saturation magnetic flux density Bs of 7,000 Gauss (0.70 Tesl).
a) A magnetic recording medium characterized by being: 2. A coercive force Hc of 2000 Oe or more, and a product of the residual magnetic flux density Br and a magnetic layer thickness δ, Br · δ, is 100 Gau.
2. The magnetic recording medium according to claim 1, wherein the coercive force squareness ratio S ^* is 0.9 or more and about ss.μm.