METALLIC MAGNETIC POWDER FOR MAGNETIC RECORDING AND ITS PRODUCTION

摘要

PURPOSE:To easily produce the metallic magnetic powder for magnetic recording excellent in oxidation resistance by coating the surface of the hydrated iron oxide grain or iron oxide grain with manganese hydroxide, calcining the grain before or after coating and reducing the coating material. CONSTITUTION:The acicular hydrated iron oxide grain having >=55m2/g specific surface or the acicular iron oxide grain having >=40m<2>/g specific surface is treated with a manganese compd. and an alkali in a liq. phase at <=pH7.5 and >=60 deg.C. Consequently, the grain surface is coated with manganese hydroxide. A reduction promoter is preferably incorporated into the hydrated iron oxide or iron oxide before or after coating. The amt. of the coating manganese hydroxide is appropriately controlled to at least 0.5wt.% as Mn/Fe based on the iron in the metallic magnetic powder. The surface can be coated with silica, as required. The grain is calcined at 550-900 deg.C after or before coating. The coating material is then reduced. A metallic magnetic powder for magnetic recording excellent in oxidation resistance and stability and capable of maintaining an excellent magnetic characteristic for a long period is obtained in this way.