JPH05128480A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To economically and stably obtain a magnetic recording medium further improved in coercive force by specifying the ratio of a particle diameter of an under film to the particle diameter of a magnetic film to improve the orientation property of the magnetic layer. CONSTITUTION:A magnetic recording medium is constituted by providing the magnetic film made from a magnetic material with the under film made from Cr or a Cr alloy on a substrate made from a non-magnetic material. The ratio of the particle diameter of the under film to the particle diameter of the magnetic film is selected from region of 0.8-1.5. The magnetic film is made from a Co-Cr alloy and the particle diameter is desirably 30-50nm. The particle diameter is controlled in the region because coercive force is lowered as the orientation property is lowered and the magnetic domain walls becomes easily movable when the diameter is out of the region.

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 for recording and reproducing information with, for example, a magnetic head, and in particular, the orientation of the underlayer and the magnetic layer is improved to increase the coercive force. It was made to become.

[0002]

2. Description of the Related Art In a magnetic disk device, a magnetic head is opposed to a magnetic recording medium at minute intervals so that the magnetic head reads magnetic information recorded on the magnetic recording medium or magnetically records the magnetic information from the magnetic head onto the magnetic recording medium. It is supposed to do. When recording and reproducing by a magnetic disk device, the magnetic head and the magnetic recording medium are, for example, 0.2 to 0.3.
It is usual to keep the distance to a minute interval of μm. Therefore, a floating head slider is used to prevent friction, wear, and / or damage caused by collision between the magnetic head and the magnetic recording medium. That is, the magnetic head slider is configured to maintain a minute gap between the two by utilizing the hydrodynamic levitation force generated in the gap between the two due to the relative velocity with the surface of the magnetic recording medium.

In order to increase the recording density of magnetic recording media, various studies have been conducted to improve the coercive force of magnetic films. For example, since the thickness of the Cr underlayer interposed between the non-magnetic substrate and the magnetic film is greatly related to the improvement of the coercive force, in order to obtain a coercive force of 1000 Oe or more, 20
There is one in which a Cr underlayer of 00Å or more is formed. However, when forming a thick Cr underlayer by sputtering,
It takes a long time for production, which is not preferable. Therefore, it is proposed that a Cr underlayer having a thickness of 1000 Å is formed on a non-magnetic substrate, and a Co-Cr-Ta film is formed thereon.

As described above, Co--Cr is formed on the Cr underlayer.
A magnetic film of -Ta is formed on the Cr layer with CoN.
It is known that the magnetic characteristics are superior to those of a magnetic layer formed of i, CoNiCr, or the like. Further, in order to improve the magnetic characteristics, a magnetic layer of CoNiPt formed on a Cr layer is disclosed in JP-A-62-141628 and JP-A-6-61628.
It is disclosed in Japanese Patent Publication No. 1-142524, and generally, the amount of Pt added is set to 15% or more to improve the coercive force. Furthermore P
Since t is expensive, in a magnetic film formed on a substrate through a Cr layer, a quaternary element of CoCrPtTa is used and a coercive force is improved as a magnetic film with a small Pt addition amount. It is disclosed in Japanese Patent No. 256017.

[0005]

As described in the above-mentioned prior art, it is possible to obtain a coercive force of 1000 Oe or more by increasing the thickness of the Cr underlayer film or by using Co-Cr-Ta as the magnetic film. However, it is not fully satisfactory as an improvement in coercive force. Further, a material obtained by adding Pt to the material of the magnetic film is expensive and not economical. It is therefore an object of the present invention to economically and stably obtain a magnetic recording medium having an improved coercive force.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have earnestly studied how to improve the orientation of the Cr underlayer and the magnetic layer in order to improve the coercive force of the magnetic recording medium. Therefore, the thickness of the magnetic film made of Co-Cr-Ta was set to 50 nm, and an experiment was conducted to see how the coercive force was affected when the thickness of the Cr underlayer was changed, and the results shown in FIG. Obtained. Then, from FIG. 1, the Cr base film is about 10
It was found that a coercive force of 1300 Oe or more can be obtained when the thickness is 0 nm or more. In addition, the thickness of the Cr underlayer is 50
An experiment was conducted to see how the coercive force was affected when the thickness of the magnetic film made of Co—Cr—Ta was changed to be nm, and the results are shown in FIG. From FIG. 2, the coercive force is 1 when the thickness of the magnetic film is thin and 40 nm or less.
I knew that it would be over 300 Oe.

From the above results, it is considered that the crystal grain size increases as the thickness of both the Cr underlayer film and the magnetic film becomes thicker. Therefore, the grain sizes of the Cr underlayer film and the magnetic film of various thicknesses are microscopic photographs. confirmed. A microstructure photograph of Cr underlayers having different film thicknesses is shown in FIG. 3, and a microstructure photograph of a magnetic film (CoCrTa) formed on these Cr underlayers is shown in FIG.
It was shown to. Further, the Cr underlayer film is kept constant and the magnetic film (CoC
FIG. 5 shows micrographs when the film thickness of rTa) was changed. Even if the substrate temperature is different from room temperature to 200 ° C., the CoCrTa film has a larger grain size than the Cr film at the same film thickness, the base film shown in FIGS.
Conditions for obtaining a high coercive force when the Ta film is thin are shown in FIGS.
Therefore, the grain size of each Cr underlayer is increased, and CoC
The condition is that the rTa grain size is small, and it can be inferred that when the grain sizes of the Cr underlayer and the magnetic layer are close to each other, epitaxial growth is facilitated and the orientation is improved. Therefore, magnetic recording media were manufactured by changing the ratio of the grain size of the Cr underlayer and the grain size of the magnetic film, and the coercive force of each was measured. The results are shown in FIG. From Fig. 6, when the particle size ratio is 1, the coercive force is 15
It was confirmed that the above assumption was correct, since the particle size ratio was 0.8 to 1.5 and the coercive force was 950 Oe or more.

The present invention has been made based on the above experimental results. That is, in a magnetic recording medium in which a magnetic film made of a magnetic material is provided on the surface of a substrate made of a non-magnetic material via a base film made of Cr or a Cr alloy, the grain size of the underlayer and the grain size of the magnetic film are A magnetic recording medium having a ratio of 0.8 to 1.5. The magnetic film is Co
-Cr alloy is used and its grain size is 30-50nm
Is desirable. The particle size is limited to the above range because if it is out of the range, the coercive force is lowered because the orientation is lowered and the domain wall is easily moved.

[0009]

In the above magnetic recording medium, since the ratio of the grain sizes of the underlayer film and the magnetic film is 0.8 to 1.5, the orientation of the magnetic film is good and therefore the coercive force is improved. ..

[0010]

Example The surface of a substrate made of an aluminum alloy containing 4% by weight of magnesium was formed into a smooth surface by turning, to obtain a substrate having an outer diameter of 95 mm, an inner diameter of 25 mm and a thickness of 1.27 mm. Next, a Ni-P alloy plating film having a thickness of 5 to 15 μm is formed on the surface of this substrate, and the contact sliding characteristics (CSS) with the magnetic head or slider at the time of starting and stopping the magnetic recording medium are measured. Secure. The surface of the plated film deposited as described above is polished to be smooth, and texture processing is performed to prevent adsorption to the magnetic head or slider.

Next, after cleaning the substrate, a base film made of Cr and Co--
A magnetic film made of a Cr-Ta alloy and a protective film made of C are sequentially laminated to form a film. In this case, to form the Cr underlayer, the sputtering chamber was evacuated to 1 × 10 ⁻⁵ Toor or less, the substrate was heated at 200 ° C. for 30 minutes, and Ar gas was introduced to maintain the sputtering chamber at 5 mToor. Depending on the conditions of input power 2000 W and film formation rate 400 Å / min,
The film was formed to have a film thickness of 60 nm and the particle size was made to be approximately 40 nm. Next, on this Cr underlayer film, Co-Cr-T
The magnetic film made of a is applied in the same manner as above, and the input power is 2000
A film having a thickness of 50 nm was formed under the conditions of W and a film forming rate of 1000 Å / min, and the particle size was made to be approximately 50 nm. The protective film was formed on the magnetic film at a film thickness of 300 Å under the conditions of an applied power of 1000 W and a film formation rate of 80 Å / min.

When the coercive force of the magnetic recording medium manufactured as described above was measured, it was 1300 Oe. Although Co—Cr—Ta was used as the magnetic film in the above-mentioned examples, it can be easily inferred that similar results can be obtained with other Co—Cr alloys, and the underlayer film is not limited to Cr. It can be inferred that the same result can be obtained even if it is made of an alloy.

[0013]

In the magnetic recording medium of the present invention, the ratio of the grain size of the undercoating film to the grain size of the magnetic film is 0.8 to 1.5, so that the orientation of the magnetic film is good and stable. Thus, a magnetic recording medium having a large coercive force can be obtained.

[Brief description of drawings]

FIG. 1 is a relationship diagram between the thickness of a Cr underlayer and coercive force.

FIG. 2 is a relationship diagram between a Co—Cr—Ta magnetic film and coercive force.

FIG. 3 is a photomicrograph of a metallographic structure showing the grain sizes of Cr underlayers having different thicknesses.

FIG. 4 is a micrograph of a metallographic structure showing the grain sizes of Co—Cr—Ta magnetic films having different film thicknesses.

5A and 5B are photographs of metallographic structures in respective cases in which the thickness of the Cr underlayer film is constant and the thickness of the magnetic film is changed.

FIG. 6 is a graph showing the relationship between the ratio of the grain size of the Cr underlayer film to the grain size of the magnetic film and the coercive force.

Claims (2)

[Claims] 1. The surface of a substrate made of a non-magnetic material is provided with Cr.
Alternatively, in a magnetic recording medium in which a magnetic film made of a magnetic material is provided through a base film made of a Cr alloy, the ratio of the particle size of the base film to the particle size of the magnetic film is 0.8 to 1.5. A magnetic recording medium characterized by: 2. The magnetic recording medium according to claim 1, wherein the magnetic film is made of a Co—Cr alloy and has a particle size of 30 to 50 nm.