Nippon Telegraph and Telephone Public Corporation

Fujitsu Corporation

Seizi Hattori

Yoshikazu Ishii

Nobuo Inagaki

Koichi Makino

Takehiko Nakagawa

Wakatake Matsuda

Kazuo Kobayashi

Susumu Kawakami

Masayoshi Shinohara

Akira Nohara

Akira Terada

A thin film of ferrite for use as a magnetic recording medium includes (a) Cu and Ti or (b) Cu, Ti and Co. The inclusion of Ti extends upwards the upper limit of the range of temperature for reducing .alpha.-Fe.sub.2 O.sub.3 to Fe.sub.3 O.sub.4, whereas the inclusion of Cu extends downwards the lower limit of this range. Further, the inclusion of both Ti and Cu enables the stable production of .gamma.-Fe.sub.2 O.sub.3 over a wide range of temperature for oxidizing Fe.sub.3 O.sub.4 to said .gamma.-Fe.sub.2 O.sub.3. The inclusion of Co improves the magnetic properties of the ferrite.

Magnetic recording medium and process for producing the same

A method of roducing .gamma.-Fe.sub.2 O.sub.3 magnetic disk medium of continuous thin film is provided, in which a deposition source is deposited on an opposed Al-alloy substrate by means of a reactive vacuum deposition technique and the deposited film is thermally treated so as to be the magnetic disk medium. As the deposition source, a ferroalloy containing about 1 to 10 at.% Ti and about 0.5 to 5 at.% Co is employed.

Method of producing magnetic thin film

A thin film of ferrite for use as a magnetic recording medium includes up to ten atomic percent of Nb based on the total number of metallic atoms in the ferrite film. This thin film of ferrite further includes up to fifteen atomic percent of Cu in addition to the Nb. The inclusion of Nb improves the squareness ratio and the coercive force of the recording medium, and also enlarges the temperature range of reduction from .alpha. -Fe.sub.2 O.sub.3 to one of the ferrites, i.e. Fe.sub.3 O.sub.4. The inclusion of Cu lowers the reduction temperature below 300.degree. C. According to the invention, a magnetic recording medium exhibiting excellent required properties, such as a high coercive force and a high squareness ratio, can be produced by a reliable process.

A thin film of ferrite for use as a magnetic recording medium contain (a) Cu, (b) both Cu and Co, or (c) Cu, Co and Nb. The inclusion of Cu increases the temperature range for reduction from .alpha.-Fe.sub.2 O.sub.3 to one of the ferrites, i.e. Fe.sub.3 O.sub.4, and also lowers the above-mentioned reducting temperature. The addition of Co improves the magnetic properties of the ferrite. The simultaneous addition of Cu, Co and Nb provides .gamma.-Fe.sub.2 O.sub.3 with excellent magnetic properties, which are stable over wide temperature range for oxidizing the Fe.sub.3 O.sub.4 to the .gamma.-Fe.sub.2 O.sub.3.

Process for producing a magnetic recording medium

In the process of sputtering of an iron target in an atmosphere composed of a mixed gas containing a rare gas and oxygen, the oxygen partial pressure is regulated prior to both presputtering and main sputtering, by which ferromagnetic oxide Fe.sub.3 O.sub.4 is deposited on a substrate in one process. By setting the temperature of the substrate at 150.degree. to 250.degree. C, the coercive force and the squareness ratio of the oxide film is greatly enhanced. By using the oxide film as a medium of a magnetic disk storage, a magnetic recording and storage device of excellent characteristics can be obtained.

Method of making a magnetic oxide film

A magnetic oxide film manufacturing method is disclosed which involves the steps of sputtering a target made of iron and aluminum to form a film of non-magnetic iron oxide (.alpha.-Fe.sub.2 O.sub.3) and reducing the film to obtain a magnetic oxide film. When a target made of iron and aluminum is employed, it is possible to obtain a high coercive force magnetic oxide film which is highly adhesive to a substrate, excellent in surface roughness and less than 0.3.mu.m in thickness. Accordingly, it is possible to obtain a magnetic disk of high magnetic recording density.

Growing community of inventors

Ibaragi, Japan

Seizi Hattori