Highly magnetic iron oxide powder

Compositions – Magnetic – Iron-oxygen compound containing

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C01G 4906

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048225096

ABSTRACT:
A highly magnetic isotropic iron oxide powder with a uniform particle size distribution and particle size in the range from 0.005 to 0.2 micrometer consists of a mixed iron oxide exhibiting gamma (Fe.sub.2 O.sub.3) and ferrite (Fe.sub.3 O.sub.4) structure, having the empirical formula Fe.sub.72-x O.sub.96, where x has a value between 2 to 7, an aspect ratio of at most 2:1 and a temperature coefficient of coercivity of less than -0.7% per degree Celcius. The mixed oxide is optionally a cobalt-modified mixed iron oxide containing 2-6% by weight of cobalt and is obtained by heating ultrafine, ferrite particles in a controlled, oxidizing atmosphere at a temperature of 240.degree. C. to 320.degree. C. for a period of one to three hours.

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patent: 4376714 (1983-03-01), Pingaud
patent: 4474653 (1984-10-01), Beer et al.
"Aging Effect of (.gamma.Fe.sub.2 O.sub.3).sub.x (Fe.sub.3 O.sub.4).sub.1-x Pigments in Magnetic Recording Tapes", Yasuo Imaoka et al., Ferrites: Proceedings of the International Conference, Jul. 1970, Japan.
"The Complete Handbook of Magnetic Recording" by Finn Jorgensen, pp. 192-193 (1986).
"IEEE Transactions on Matnetics", vol. MAG-22, No. 5, pp. 741-743 (1986).
"IEEE Transactions on Magnetics", vol. MAG-8, p. 648 (1972).
"IEEE Transactions on Magnetics", vol. MAG-18, No. 6, 1083 (1982)-`High Coercivity Particulate Magnetic Media In-Situ Partial Reduction of gamma Fe.sub.2 O.sub.3 and Modified gamma Fe.sub.2 O.sub.3 ' by V. M. De Palma et al.

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