| 摘要 |
PURPOSE:To improve an S/N by using Co-containing iron oxide magnetic powder containing Fe<2+> and Co<2+> on its surface so that atom ratios Fe<2+>/Co<2+> and Co<2+>/Fe<3+> are included in specific ranges respectively. CONSTITUTION:In a magnetic recording medium using magnetic powder obtained by forming magnetic iron oxide containing Co atoms on the surface of needle- shaped magnetic iron oxide powder as a recording element, Fe<2+> and Co<2+> are contained in the magnetic powder so that atom ratios Fe<2+>/Co<2+>>=3 and Co<2+>/ Fe<3+=0.015 are satisfied. The magnetic powder having 20m<2>/g or more specific surface area is preferably used. In a method producing cobalt-deposited magnetic iron oxide powder by adding magnetic iron oxide powder together with an alkaline solution into a suspension containing Co<2+> ions, Fe<2+> ions and other metallic ions and mixing these components, said magnetic powder can be produced by reacting respective components at the composition satisfying Fe<2+>/Co<2+> >=10 and Co<2+>/Fe<3+=0.015 in mole ratio. |
