| 摘要 |
PURPOSE:To obtain magnetic powder undergoing no reduction in deltas and having superior transferability, an excellent form and high coercive force by simultaneously reacting needlelike magnetic iron oxide with Co<2+> and Fe<2+> in alkali to form a Co-Fe cpd. layer on the iron oxide surface. CONSTITUTION:Needlelike magnetic iron oxide as seed crystal represented by O< Fe<2+>/Fe<3+0.5 is dispersed in an aq. soln. contg. Co<2+> and Fe<2+>, and 3-12mol/l of alkali is added to the soln. The iron oxide and the ions are then reacted at 80- 100 deg.C in an oxidizing atmosphere to form a Co-Fe cpd. layer, on the iron oxide surface, e.g. obtd. by crystallization of cobalt ferrite. The ratio of Fe<2+>/Co<2+> in the dispersion is pref. adjusted to 4 or below. In case of Fe<2+>/Co<2+>>4, a nonmagnetic substance is formed to reduce magnetic quantity deltas. |
