Tdk Electronics Company, Limited

Toshihiro Hamabata

Shinji Umeki

Kazuo Takada

Kazuaki Onuki

A magnetic iron oxide powder having high coercive force is produced by dispersing a magnetic iron oxide comprising a silicon component and a phosphorus component in an aqueous solution of a cobalt ion and adding a base to the dispersion to be an alkaline condition and heat-treating the dispersion whereby the cobalt ion is adsorbed and diffused in the surface layer of the magnetic iron oxide. A zinc component can be also incorporated in the crystal. The silicon component and the phosphorus component are preferably incorporated in the crystalline structure.

Process for producing magnetic powder having high coercive force

An alkali hydroxide is added to an aqueous solution of ferrous salt to form a precipitate and a part of the solution is separated to control a ratio of an anion to a ferrous component to less than 1 and the ferrous component is oxidized to acicular goethite with an alkali metal chlorate such as potassium chlorate.

Process for producing acicular goethite

An alkali hydroxide is added to an aqueous solution of ferrous salt to form a precipitate and a part of the solution is separated to control a ratio of an anion to a ferrous component to less than 1 and the ferrous component is oxidized to acicular goethite by bubbling air through the supernatant and precipitate.

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Tokyo, Japan

Toshihiro Hamabata