COBALT-CONTAINING ACICULAR FERRIMAGNETIC IRON OXIDE OF IMPROVED REMANENCE STABILITY

摘要

In the production of acicular ferrimagnetic gamma -iron oxide containing about 0.5 to 10 atom % of cobalt including the steps of producing cobalt-containing iron oxide hydroxide, dehydrating the oxide hydroxide to oxide, reducing the oxide and re-oxidizing it into ferrimagnetic iron oxide, the improvement which comprises tempering the material at a temperature of about 600 DEG to 800 DEG C prior to dehydration or reduction, whereby the resulting ferrimagnetic iron oxide upon being thermally stressed retains more than 90% of its remanence.