A Co- and Fe-containing ferromagnetic iron oxide powder having a high coercive force and improved stability to heat and pressure is produced by adding an aqueous alkali solution, an aqueous solution containing Co.sup.+2 ions, and an aqueous solution containing not more than 1 equivalent, based on the Co.sup.+2 ions, of Fe ions to a suspension of ferromagnetic iron oxide, and heating the mixture at a temperature of at least 80.degree. C in the presence of an oxidizing agent. The ferromagnetic iron oxide powder is especially suitable for producing magnetic recording media.
一种含有Co和Fe的
铁氧体粉末,具有高的矫顽力和改善的耐热性和耐压性,通过向
铁磁性
铁氧体悬浮液中添加
水溶性碱溶液、含Co.sup.+2离子的
水溶液和不超过1当量的含Fe离子的
水溶液,并在氧化剂存在下以至少80℃的温度加热混合物而制成。该
铁氧体粉末特别适用于生产磁性记录介质。