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

摘要

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): 20 -16.70 0.10 <+>/total Fe where SSA is a BET specific surface area (m<2>/g), and V is a magnetic switching unit (cm<3>), can be produced by producing iron oxide particles having a concentration of Fe<2><+> of 0.10 to 0.36 as expressed by Fe<2><+>/total Fe from the precursor, gamma -FeOOH, and coating a cobalt compound or a combination of a cobalt compound and other metal compounds on the surfaces of the iron oxide particles.