COBALT-CONTAINING IRON OXIDE PIGMENT, ITS PRODUCTION AND MAGNETIC RECORDING MEDIUM CONTAINING THE SAME

摘要

PURPOSE:To produce a cobalt-containing iron oxide pigment which is improved in a magnetic characteristic with lower cobalt content and having high coercive force. CONSTITUTION:In the cobalt-containing iron oxide pigment consisting of a cobalt containing iron oxide core part and the cobalt-containing iron oxide surface part containing the higher concn. cobalt than the core part, the average concn. of the cobalt dispersed within the range of 50wt.% of the innermost side of above core part is 0.1-1.0wt.% expressed in terms of cobalt per iron oxide incorporated within the range of 50wt.% of the innermost side of the core part, and the Fe<2+> content in the core part is 16-22wt.% per iron oxide incorporated in the core part, and the cobalt concn. in the surface part within the range of 10wt.% of the outmost side of the pigment is at least 5 times in average of the cobalt concn. within the range of 50wt.% of the innermost of the core part.