| 摘要 |
PURPOSE:To obtain a magnetic card having a high squareness ratio and recording density, by blending a compound of Ba and/or Sr with iron oxide, Al2O3, SiO2, BaCl2 and/or Bi2O3 in specific amounts and firing and pulverizing the resultant blend under given condition. CONSTITUTION:A mixture of a compound of Ba and/or Sr with Fe oxide is blended with Al2O3, SiO2, BaCl2 and Bi2O3 and the amounts thereof based on the above-mentioned Fe oxide (expressed in terms of Fe2O3) are adjusted as follows. 0.05-3wt.% Al2O3, 0.1-3wt.% SiO2, 0.95-25wt.% BaCl2 and/or 0.25-1.5wt.% Bi2O3. The obtained blend is then fired at 800-1,100 deg.C temperature and pulverized. Thereby the aimed magnetoplumbite type ferrite particulate powder having 0.2-0.7mum average particle diameter measured by the Fischer subsieve sizer method and >=0.92 orientation degree (Br/4piIs) is obtained. |
