| 摘要 |
PURPOSE:To obtain super-fine particles in uniform particle size having an excellent magnetic characteristic as the coating film type magnetic medium for vertical magnetic recording by generating magnetite fine particles coprecipitating Pb, Ba, Sr by the wet method allowing coexistence of silicate and then baking such particles at a particular temperature. CONSTITUTION:An aqueous solution containing one or more kinds of metal salts of Pb, Ba, Sr and ferrous salt in such a composition as generating hexagonal system ferrite and an aqueous solution containing one or more kinds of alkali hydroxide, alkali carbonate, ammonium and ammonium carbonate as the alkali agent are mixed under the condition for generating magnetite. On the occasion of oxidizing it with air, a water-soluble silicate is added to said mixed solution for coexistence and thereafter Si is deposited. Thereby, the magnetite coprecipitating Pb, Ba, Sr can be manufactured. This coprecipitated magnetite is washed by water, filtered and dried up, and then baked at a temperature of 400-900 deg.C in order to obtain the hexagonal system ferrite super-fine particles. |
