JPS58130438A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the wear resistance of a vertically magnetizable thin Co-Cr alloy film as a magnetic recording medium by forming a thin beryllium oxide film oriented vertically in the direction of the C axis on the surface of the Co-Cr alloy film. CONSTITUTION:A Co-Cr alloy film 3 as a vertical magnetization recording film is formed on a substrate 1 with a magnetic film 2 having small coercive force in-between. The film 2 includes a thin ''Permalloy '' film. An oriented thin beryllium oxide film 9 is then deposited on the film 3 in about 1,000Angstrom thickness by ionic plating, magnetron sputtering or other methods.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium in which a thin film of cobalt chromium oxide is formed with a button orientation perpendicular to the surface of the magnetic recording medium.

In recent years, with the development of VTRs and the popularization of computers, the density of magnetic recording tapes and magnetic recording disks has rapidly increased. Among them, the magnetic recording method called perpendicular magnetization recording is attracting the most attention. The recording medium used in the perpendicular magnetization recording method is as shown in FIG. A cobalt chromium alloy film 3 containing 3% is formed.The cobalt chromium alloy film 3 formed on the top has a property of being easily magnetized perpendicular to the substrate 1.To this new recording medium A magnetic head with a new structure is used for recording and reproducing.

The outline is shown in Figure 2. A tanzak-shaped permalloy film called a main magnetic pole 5 is formed on the top of the cobalt-chromium alloy recording medium 4, and on the opposite side there is arranged a magnetic pole called an auxiliary magnetic pole 6 in which a coil is wound around a rod-shaped ferrite. A magnetic head having this structure performs recording and reproduction on a sicobalt chromium alloy recording medium.

Cobalt chromium alloy has a hexagonal 2-close-packed crystal structure, and when a thin film is formed by sputtering at an argon pressure of about 0.01 Torγ, it becomes a cylindrical structure that stands perpendicular to the substrate surface. Magnetic anisotropy occurs. The situation is shown in Figure 3.

A cylindrical microcrystal 7 extending in the C-axis direction stands on a substrate 8. The clearer the α-axis is perpendicular to the substrate, the higher the magnetic anisotropy, the easier recording, and the higher the reproduction output. This deviation from the vertical direction can be measured by X-ray diffraction and is called a rocking curve, Δθ.

It is known for its characteristics. In other words, the rocking curve as shown in Figure 4 shows that the cobalt chromium thin film is normally
below. That is, most of the cylindrical microcrystals have their α-axes aligned within 5 degrees from the direction perpendicular to the substrate. Normally, in the case of a cobalt-chromium alloy thin film formed by sputtering on a PET substrate or an aluminum substrate, Δθ5G is 3 degrees or less.

Usually, a magnetic film with low coercive force, such as a thin film of permalloy, is further formed under the cobalt-chromium alloy thin film to enable high-density recording and achieve low noise and high reproduction output. Therefore, a thin film of permalloy or cobalt chromium alloy is usually formed on a flexible substrate such as PIT, each having a thickness of about 5000 angstroms, and the metal surface of the recording medium is left exposed. Because of this structure, the surface of the magnetic recording medium using conventional YFg203 exhibits a completely different phenomenon. In particular, when a recording/reproducing head slides on the surface, it is more susceptible to scratches than conventional magnetic recording media, and there are concerns about long-term reliability. The present invention eliminates this drawback and completes a highly reliable high-density magnetic recording medium.

An object of the present invention is to provide a highly reliable magnetic recording medium.

Another object of the present invention is to provide a magnetic recording medium with high recording density.

The invention will be explained below with reference to the figures.

FIG. 5 is a diagram illustrating the present invention in detail. The basic structure is the same as that of the conventional structure in that a permalloy film 2, which is a small coercive force magnetic film, and a cobalt chromium alloy film 4-3, which is a perpendicular magnetization recording film, are formed on the substrate 1, but the present invention further improves the structure. Oxidized IJ as a wear-resistant layer
By forming a lium thin film 9, reliability has been dramatically improved. That is, by forming a thin film of beryllium oxide BeO with a thickness of approximately 1,000 angstroms, it was possible to ensure reliability for more than 1 million buses on the same track. Whether the substrate 1 is rigid such as aluminum or flexible such as PFiT or polyimide, the effect of forming a beryllium oxide thin film is similarly obtained. A main magnetic pole 5 and an auxiliary magnetic pole 6 are fixed to both sides of the recording medium by sliders 10 made of a material such as titanium burr, so as to ensure smooth sliding on the recording medium.゛Reliability improves as the thickness of barylium oxide Be09 increases, but the thicker the layer, the longer the distance between the perpendicular magnetization recording film 2 and the tip of the main pole 5, which reduces the reproduction signal output and reduces noise. Therefore, the thickness of the beryllium oxide 13 go is determined in consideration of the characteristics of the perpendicular magnetic recording film 2 and the head. In FIG. 5, the head has a main magnetic pole 5. Auxiliary 5-Although the basic type in which the magnetic poles 6 are opposed to each other has been described, it goes without saying that the present invention has similar effects on heads that are improved from this basic type and on ring-type heads.

The crystal structure of aluminum oxide Beo is shown in Figure 3.
It has an hcp structure exactly the same as the crystal structure of the cobalt chromium thin film shown in FIG. 4, and the shortest interatomic distance on the α axis is 111f2. s2 angstroms, whereas that of beryllium oxide thin film is 2 angstroms.
．． It is very close to 7 angstroms. Therefore, by controlling the conditions for forming a beryllium oxide thin film, it is possible to epitaxially grow it on a cicobalt chromium film.

That is, the beryllium oxide thin film is oriented perpendicularly to the surface of the cobalt chromium thin film. At that time, Δθ5° takes a value similar to that of the cobalt chromium thin film. By forming the beryllium oxide thin film BeO with such orientation, the wear resistance was improved and the reliability was more than double that of the case without orientation. These oxidized PeIJI
Formation of the Jium thin film 61 is performed by ion blating, magnetron sputtering, etc., and a film with good orientation was obtained by magnetron sputtering. In the recording medium, the low coercive force magnetic film may be made of a material other than permalloy, but the effects of the present invention remain the same, and the same holds true even when there is no low coercive force magnetic thin film at all. The invention will be explained below with reference to examples.

Example 1 Permalloy film 5000 on a 50 micron thick PET substrate
Angstrom, cobalt chromium alloy film 6000
Argon partial pressure 3x Ill”-3 Torr,
The beryllium oxide thin film was formed to a thickness of 500 angstroms under an oxygen partial pressure of 2.times.X and Hl-'Torr, and the .DELTA..theta.5o of the beryllium oxide thin film was 5 degrees. When a head was mounted on this recording medium, the signal output normally decreased after about 100,000 passes, but no decrease in signal output was observed even after 2 million passes.

7-

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a conventional perpendicular magnetization recording medium. FIG. 2 is a diagram illustrating a magnetic head having a main magnetic pole and an auxiliary magnetic pole. FIG. 3 is a diagram illustrating the crystal structure of a cobalt chromium alloy thin film. FIG. 4 is a diagram explaining the rocking curve. FIG. 5 is a diagram explaining the present invention. 1. Substrate 2. Permalloy film 3. Perpendicular magnetization film
4. Magnetic recording medium 5. Main magnetic pole 6. Auxiliary magnetic pole
7...Cylindrical microcrystal 8...Substrate 9...Beryllium oxide thin film 10...Slider or more Applicant: Suwa Kozukosha Co., Ltd. 8- 1. Hatata 2. → θ

Claims (1)

[Scope of Claims] A thin film magnetic recording medium mainly made of an alloy of cobalt and chromium, characterized in that a benzene oxide thin film is formed on the surface of the cobalt chromium thin film. 2. The magnetic recording medium according to claim 1, wherein the C-axis direction of the crystal of the C21 beryllium oxide thin film is oriented perpendicular to the surface of the cobalt chromium alloy thin film.