Process for producing magnetic powder having high coercive force
AssigneeTDK Electronics Co., Ltd.
InventorsShinji Umeki, Kazuo Takada
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Abstract
A magnetic iron oxide powder which has high coercive force and stable magnetic characteristics is produced by forming a surface layer of the magnetic iron oxide powder which comprises a cobalt compound as a main component. The magnetic iron oxide powder is treated with an aqueous solution of a cobalt ion for two times or more to form at least two surfaces comprising the cobalt compound.
Claims1
A process for producing a magnetic iron oxide powder with at least two surface layers, each layer comprising a cobalt compound, which comprises forming on .gamma.-Fe.sub.2 O.sub.3 powder a first surface layer by treating said .gamma.-Fe.sub.2 O.sub.3 powder with an aqueous solution of cobalt sulfate, subjecting the resultant single-layered product to an extended heating period in boiling aqueous alkali solution, forming on said single-layered product a second surface layer by treating said single-layered product with an aqueous solution of cobalt sulfate, subjecting the resultant twice-layered product to an extended heating period in boiling aqueous alkali solution, and recovering the at least twice-layered product.
Dependencies are inferred from the claim text.