JPS62137720A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To securely stick a magnetic material to a substrate and to remarkably improve the coercive force of the magnetic material by using a chromium film as an underlying layer. CONSTITUTION:The underlying layer essentially consisting of chromium is provided on the substrate and the magnetic layer consisting of a cobalt-platinum alloy is provided on the underlying layer. The thickness of the underlying layer consisting of the chromium film is preferably in a 10-10,000Angstrom range. The effect of improving the coercive force is low and the ratio of the fluctuation of the coercive force to the change of the thickness is high if the thickness is <=10Angstrom . The magnetic recording medium having the stable coercive force is then not obtainable. The coercive force is substantially high and the fluctuation of the coercive force as compared to the change of the thickness is relatively small if the thickness of the chromium layer is within the 100-10,000Angstrom range and therefore, said range is more particularly preferable in general. There is no particular improvement of the coercive force if the chromium layer is made thicker than the specified range. In addition, such is uneconomical.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Sedentary Use) The invention relates to magnetic recording media such as magnetic disks, magnetic rams, and magnetic tapes.

(Prior Art) In recent years, there has been a strong desire for high-density recording media in magnetic recording media, and as a result, multi-layer thin film media in which a magnetic layer is a magnetic layer have been attracting attention.

As such continuous reading thin model magnetic recording media, those made of alloys such as cobalt-valine and cobalt-nickel-phosphorus are known.

In addition, new high-density information signal recording methods such as magneto-optical recording and perpendicular magnetic recording have been proposed and researched as a method for achieving even higher density. On the other hand, the conventional longitudinal recording (in-plane recording) method has a sufficient industrial track record as a recording method, and the improvement in recording density with this method is of great industrial significance.

Recently, in order to meet the demand for higher density, studies are underway on the Z5 technology, in which the floating spear of the magnetic head V is made smaller and recording/reproduction is performed with the magnetic head V almost in contact with the medium. When using a contact type magnetic head like this, a magnetic thin J
By increasing the total coercive force of the
It is known that t can be improved.

Conventional methods for obtaining a magnetically antimagnetic metal thin film using vacuum waves include: - magnetic material, #4 alloy abrasion, (heat treatment of bronze monument material), - tilted vapor deposition method, and - control by base material. , a method has been proposed.

However, when comparing the above-mentioned cobalt-phosphorous alloys, cobalt-nickel alloys, etc. at a film thickness of about 100 mm, the coercive force is only about 300 to 1000 F.V.

Cobalt-platinum alloy is known as an alloy with high coercive force in terms of specificity and convergence, but even this is limited to about 1000 oersted, which is still not a satisfactory coercive force. The disadvantage is that the adhesion to the underlying layer is insufficient. Additionally, a method using a vanadium-platinum-cobalt alloy or a tungsten-platinum-cobalt alloy (Japanese Unexamined Patent Publication No. 1988-88807), a method using a vanadium-platinum-cobalt alloy,
Method using cobalt-zoraceodymium alloy (JP-A-59
A method is known in which a ternary alloy such as Japanese Patent No. 227106 is attached to a substrate by sputtering.

(Problems to be Solved by the Invention) According to these methods, a magnetic thin film with a coercive force of up to 1300 oersted can be obtained, but when sputtering a six-element alloy, care must be taken to control the composition, and a slight Coercive force tends to fluctuate greatly due to errors in composition.

It is an object of the present invention to provide four aeration records that are made of an alloy with a simple composition and stably have a strong coercive force.

(Means for Solving the Problems) The present inventors have been thoroughly considering a method for treating the base of a magnetic material made of a cobalt-platinum alloy, and found that the base, Ii
It has been found that by using a chromium film as a chromium film, not only the above-mentioned magnetic substance is firmly attached, but also the coercive force of the magnetic substance is significantly increased. The magnetic recording medium of the present invention is based on the above findings. That is, the present invention is characterized in that a base layer containing chromium as a main component is provided on a substrate, and a magnetic material made of a cobalt-platinum alloy is provided on the base layer.

The present invention will be explained in detail below. The substrate of the present invention is a hard molded product such as an aluminum plate, a glass plate, a synthetic tree, or a plastic material, or a soft film such as an aluminum foil or a polyester film. The surface of the substrate must be thermally straightened and polished by conventional methods to sufficiently reduce waviness and unevenness.

The chromium of the underlayer may be deposited by either plating or sputtering, but its thickness is particularly important. The thickness of the base layer made of chromium film is 10^~1ooo
A range of o^ is desirable.

If it is less than 10, the effect of improving coercive force is small, and the rate of change in coercive force with respect to change in thickness is large, making it impossible to obtain a magnetic recording medium with stable coercive force.

When the thickness of the chromium layer is in the range of 100λ to 1oooooA, the coercive force is sufficiently high, and the change in coercive force due to changes in thickness is relatively small, so this range is generally particularly preferred. Even if the chromium layer is made thicker than this, the coercive force does not particularly increase, and this is uneconomical.

The magnetic layer made of a cobalt-platinum alloy in the present invention is deposited by sputtering. Cobalt 11 Δ /r
1 va c-* I++ If l mouth-
1% -1+J Il, L J? 7
n -- n ○ d 2 to 30% platinum is preferred. According to the experimental results of the present inventors, the coercive force of a magnetic layer made of cobalt and platinum is highest when the atomic ratio of cobalt is around 80%, and the coercive force decreases even if the cobalt content is higher or lower than that. There was a tendency to If the composition is outside the above range, the coercive force becomes too small, which is not preferable.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

The example substrate has an outer diameter of 90 mm, a thickness of 25.8 m, and a thickness of 1.5 m.
A 2 ms aluminum disk was prepared. After lapping the surface of the substrate, a hard layer of nickel and phosphorus with a thickness of 30 μm was provided by a non-core plating method. After mirror polishing the hard layer, the substrate was sputtered using a magnetron sputtering device (Tokuda A
It was fixed on a sample stand of CFS-sES Cedar manufactured by Seisakusho. Magnetoon sputtering equipment was activated, and the argon gas pressure was 2 x 10-2 torr.

A chromium film was deposited with gold 4 chromium as tarded under sputtering power of 4 W, <y" and DC sputtering conditions. Next, argon gas pressure was set to 2 x 10-2 torr.
.

Sputtering power 6 W/E, m2, RF sputtering conditions, cobalt-platinum (atomic ratio 82:18) t-tarded, cobalt-platinum alloy thickness 1000
A film of X was attached to form a magnetic recording medium.

The thickness of the chromium film can be increased from 10^ to ioooo by repeating the above process for preparing the magnetic recording medium and changing the chromium sputtering time in stages.

Seven magnetic recording media having different thicknesses were manufactured.

The coercive force of these magnetic recording media was measured. Coercive force was measured using a vibrating sample sensitometer (model BH) manufactured by Riken Denshi.
V-55) with a Gaussian external magnetic field of 15. In Table 1, the horizontal axis of measured coercive force and underlayer 7 is on a logarithmic scale. This graph shows that the coercive force increases markedly with the adhesion of chromium, and when the thickness of the chromium layer is 5000 oersted, the coercive force reaches 6500 oersteds, and when the chromium layer is thicker than this, the coercive force hardly increases and becomes stable. I understand that.

Next, among the above magnetic recording media, the recording/reproducing frequency % for the medium with a chromium layer thickness of 50 thick and the medium with 100 thick chromium layers.
The sex was measured. In this case, the magnetic head is an amorphous metal head (ring type), and the relative speed is 10 m/s.
ee, ) The rack width is 20 μm. Both the horizontal and vertical axes of the graph are on a logarithmic scale. From this graph, it is clear that the thicker the chromium layer, the smaller the drop in output in the high frequency range, the better the frequency characteristics, and therefore the higher the recording/reproduction capability.

Figure 6 shows the results of testing the adhesion force of the magnetic layer of the magnetic recording medium thus obtained. What is the tape peel test? Use a knife to carve one pitch of base lines on the media surface, 10 rows in each direction (100 rows in total), apply cellophane tape on top of it, then peel it off and check the number of rows that have peeled off on the media surface. A still life test is a test in which a magnetic disk is set in a disk drive device, the magnetic head is fixed only on a certain track of the magnetic disk, and the magnetic disk is rotated for a long period of time to see if islands fit into the trunk. The durability of the magnetic layer is investigated by examining the .

As shown in Table 6, the adhesion of the magnetic layer was strong in those having the chromium film underlayer.

Table 1 Table 2 Table 3 Comparative Example Compared to the example in which magnetic recording was performed using the same method and under the same conditions as in the practical example, except that the chromium film was not deposited by sputtering, the output in the high frequency range was significantly reduced. It was tough. Further, as shown in Table 6, the results of testing the adhesion force of the magnetic layer of this medium were determined to be weaker than in the practical example.

(Effects of the Invention) According to the present invention, a magnetic recording medium having high coercive force, excellent frequency characteristics, and high durability of the magnetic layer can be obtained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the thickness of the underlying chromium layer and coercive force, and FIG. 2 is a graph showing frequency characteristics. Patent Applicant Denki Kagaku Kogyo Co., Ltd. Figure 1 Thickness of 70 μm layer of bottom manure (people) Figure 2 Commissioner of the Japan Patent Office Michibe Uga1, Indication of the case Patent Application No. 276137 of 19552, Name of the invention Magnetic recording medium3, Person making the amendment Relationship to the case Patent applicant address ■100 Yurakucho, Chiyoda-ku, Tokyo Column 5 of Detailed Description of the Invention in Specification No. 1-4-1, Contents of Amendment

Claims (3)

[Claims] (1) A magnetic recording medium characterized in that an underlayer containing chromium as a main component is provided on a substrate, and a magnetic layer made of a cobalt-platinum alloy is provided on the underlayer. (2) The magnetic recording medium according to claim (1), wherein the underlayer has a thickness of 10 Å or more. (3) Claim 1, wherein the cobalt-platinum alloy has a composition of 70 to 98% cobalt and 2 to 30% platinum (atomic ratio), and the thickness of the magnetic layer is 300 Å to 5000 Å.
Magnetic recording medium described in Section 1.