JPH0125211B

PURPOSE:To obtain the magnetic metal fine grain retaining corpuscular shape while having the proper value of coersive force by a method wherein two layers consisting of a metal layer of at least one kind metal selected from nickel, calcium or manganese, and a layer of a silicon oxide are adhered on the surface of metallic iron particles. CONSTITUTION:The wet cakes of alpha-oxy-iron hydroxide are suspended in water, an organic acid is added thereto to make hydrogen ion concentration thereof to 4.0pH or less. A metal salt is added thereto, then ammonium is added thereto to form slurry of 9.0-11.0pH. After aging is performed by heating at 70 deg.C or more, a silicic acid aqueous solution is added to be treated, and thus obtained slurry is separated according to the filtration method, etc. After thus obtained treated alpha-oxy-iron hydroxide is dried, it is heated to be reduced. Accordingly the magnetic metal fine grain adhered with the two layers of the metal layer and the silicon oxide layer can be obtained. Moreover the Si adhering ratio is made to 0.5-3.5wt%, and 0.8-1.3wt% is favorable, metal/Fe (the atomic weight ratio) or the metal compound is made to 1-10, the specific surface area is made to 30-70m /g, and 30-55m /g is favorable.