| 摘要 |
PURPOSE:To develop hexagonal ferrite for a magnetic recording medium which is extremely fine and excellent in dispersibility and crystallinity and suitable for high-density recording by adding a specified flux to hexagonal powder which is obtained by subjecting a compd. contg. both trivalent Fe compd. and a specified compd. to hydrothermal treatment and heat-treating the mixture. CONSTITUTION:Both trivalent Fe compd. such as ferric chloride, ferric nitrate and ferric sulfate and a compd. contg. at least one kind of chloride, nitrate, hydroxide and carbonate of Ba, Sr and Pb are subjected to hydrothermal treatment for 1-5hr at 200-300 deg.C together with alkali such as KOH and NaOH and hexagonal ferrite powder having <=0.1mum particle diameter is produced. BaCl2 is individually mixed to this powder or after mixing BaCl2 with alkali halide such as NaCl and KCl, the mixture is mixed thereto in proportion of (1:3)-(1:20) for the hexagonal ferrite and heat-treated in air at 700-900 deg.C for 1-10hr. |
