| 摘要 |
PURPOSE:To reduce temperature dependency of coercive force of magnetic grains by composing from displacement hexagonal ferrite which has specific size range and coercive force and whose Fe atom is displaced with In of specific number of atoms per one chemical formula. CONSTITUTION:Magnetic powder consists of displacement hexagonal ferrite which has an average particle diameter of 0.02-0.2mum and a coercive force of 200-2000Oe and whose Fe atom is displaced with In of number of atoms of 0.05-1.0 per one chemical formula. Co-Ti displacement hexagonal ferrite crystal expressed by the following usual equation is a typical example; AFe12-2x-yCoxTixInyO19 (A is an element chosed from Ba, Sr, Pb and Ca.), where 0.2<=x<=1.2 and 0.05<=y<=1.0. To manufacture the magnetic powder, oxide and carbonation of each element necessary for forming hexagonal ferrite are dissolved together with glass formation substance, the melt is quenched to form glass, crystal grains of hexagonal ferrite are precipitated by heat treatment at a specified temperature, then glass composition is eliminated by heat treatment. Temperature characteristics of coercive force of magnetic powder and the recording medium using them can be thereby improved. |
