Process for producing cobalt-modified ferromagnetic iron oxide

摘要

A process for preparing cobalt-modified ferromagnetic iron oxide by modifying ferromagnetic gamma -Fe2O3 particles with cobalt, wherein prior to cobalt modification treatment, the ferromagnetic gamma -Fe2O3 is heat treated at a temperature in the range of from about -200 DEG C. to +30 DEG C. of the critical temperature at which partial transition of gamma -Fe2O3 into alpha -Fe2O3 occurs and which reduces the saturation magnetization to 99% of the saturation magnetization measured before the heat treatment, and the atomic ratio of Fe++/Fe+++ after the cobalt modification is 0.00 to 0.10.