Magnetic recording medium and process for producing the same
AssigneeFujitsu Limited
InventorsSeizi Hattori, Koichi Makino, Takehiko Nakagawa, Masayoshi Shinohara
Life of this patent
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Abstract
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.
Claims12
A process for producing a magnetic recording medium of a thin film of ferrite, comprising the steps of:
- forming a thin film of .alpha.-Fe.sub.2 O.sub.3 containing Cu in an amount of from 1 to 15%, Ti in an amount of from 1 to 10% and Co in an amount of from 1 to 10%, based on the number of atoms of Fe of said ferrite;
- reducing said .alpha.-Fe.sub.2 O.sub.3 to Fe.sub.3 O.sub.4 by heating said .alpha.-Fe.sub.2 O.sub.3 at a temperature in the range of from 225.degree. to 400.degree. C. in a reducing atmosphere;
- and,
- oxidizing said Fe.sub.3 O.sub.4 to .delta.-Fe.sub.2 O.sub.3 by heating said Fe.sub.3 O.sub.4 at a temperature in the range of from 150.degree. to 450.degree. C. in an oxidizing atmosphere.
A process for producing a magnetic recording medium of a thin film of ferrite, comprising the steps of:
- forming a thin film of .alpha.-Fe.sub.2 O.sub.3 containing Cu in an amount of from 2.5 to 7.5%, Ti in an amount of from 2.5 to 7.5% and Co in an amount of from 2 to 8%, based on the number of atoms of Fe of said ferrite,
- reducing said .alpha.-Fe.sub.2 O.sub.3 to Fe.sub.3 O.sub.4 by heating said .alpha.-Fe.sub.2 O.sub.3 at a temperature in the range of from 250.degree. to 350.degree. C. in a reducing atmosphere;
- and,
- oxidizing said Fe.sub.3 O.sub.4 to .gamma.-Fe.sub.2 O.sub.3 by heating said Fe.sub.3 O.sub.4 at a temperature in the range of from 200.degree. to 450.degree. C. in an oxidizing atmosphere.
A method of reducing a film of .alpha.-Fe.sub.2 O.sub.3 within a broadened temperature range comprising
- forming said film to comprise Cu from 1 to 15% and Ti from 1 to 10%, based on the number of Fe atoms of said film, and
- reducing said film to Fe.sub.3 O.sub.4 in a reducing atmosphere at a temperature between 225.degree. and 400.degree. C.
A method of oxidizing a thin film of Fe.sub.3 O.sub.4 to .gamma.-Fe.sub.2 O.sub.3 at a temperature within a broadened temperature range to have a coercive force over 500 Oe and a squareness ratio over 0.5 comprising
- forming said thin film of Fe.sub.3 O.sub.4 to comprise 1 to 15% Cu, 1 to 10% Ti and 1 to 10% Co based on the number of atoms of Fe of said Fe.sub.3 O.sub.4, and
- oxidizing said thin film of Fe.sub.3 O.sub.4 to .gamma.-Fe.sub.2 O.sub.3 in an oxygen-containing atmosphere at a temperature in the range from 150.degree. to 450.degree. C.
Dependencies are inferred from the claim text.