| 摘要 |
PURPOSE:To improve coercive force with retaining good inversion magnetic distribution, by regulating the pH of the slurry dispersed with coated material obtd. by coating a specified powder with Al or Mn compd., to a fixed value and by heat-treating. CONSTITUTION:The slurry having 0.01-3M/l concn. of OH group is obtd. by dispersing the magnetic iron oxide (A) powder obtd. by partially reducing Fe3O4, etc., in an aq. liq. medium and by adding Co salt, ferrous salt and alkali. The slurry is treated at room temp. - 100 deg.C for 0.1-10hr in the non-oxidative atmosphere to obtain a slurry (B) dispersed with the coated material obtd. by coating the surface of (A) component with metal compd. contg. 0.5-30wt.% Co salt and ferrous salt. Then, the targeted coated material (C) is obtd. by adding with H2SO4, etc., to (B) component to adjust the pH of the slurry (B) to 7-10.5, by treating by furthermore adding AlCl3, MnSO4, etc., to coat with 0.01-3wt.% as A or Mn to (A) component. Then, the ferromagnetic iron oxide contg. cobalt is produced by treating (C) component by heating at 70-150 deg.C for 1-10hr. |
