Ishihara Sangyo Kaisha, Ltd.

Shigeru Takatori

Arata Koyama

Tokuo Suita

Nobusuke Takumi

Makoto Ogasawara

Kiyoshi Asano

Kouichi Tamura

Cobalt-containing magnetic iron oxide particles extremely suitable for magnetic recording mediums, especially for image recording mediums and a process for producing the same from the precursor, .gamma.-FeOOH which is advantageous in industry are disclosed. Cobalt-containing magnetic iron oxide particles satisfying the following equations (1), (2) and (3):

Cobalt-containing magnetic iron oxide and process for producing the same

A process for producing magnetic ion oxide particles for magnetic rcording which comprises heat-treating a magnetic iron oxide particles of magnetite, berthollide or maghemite as a starting materials, in the presence of a zinc component or both a zinc component and a silicon component at a temperature of 400.degree. to 700.degree. C. in a specific atmosphere, and if necessary, subjecting the heat-treated particles to wet treatment and/or dry treatment, thereby doping the particles with zinc ions resulting in magnetic iron oxide particles having an improved saturation magnetization, a proportion of said zinc ions being 2 to 9 at. % by weight relative to the total amount of iron ions.

Process for producing magnetic iron oxide particles for magnetic

Growing community of inventors

Moriyama, Japan

Shigeru Takatori