| 摘要 |
PURPOSE:To obtain W-phase type hexagonal ferrite particles having considerably improved coercive force and squareness ratio by calcining a mixture consisting of the carbonate or oxide of a specified metal, the oxide of a specified metal and iron oxide and by carrying out physical pulverization and annealing. CONSTITUTION:At least one kind of compound selected among the carbonates and oxides of Ba, Sr, Pb and Ca is mixed with at least one kind of compound selected among the oxides of Cu, Zn, Ni, Co, Mn, Mg and Fe and compounds convertible into the oxides by heating and iron oxide or an iron compound convertible into iron oxide by heating. The mixture is calcined, physically pulverized, and annealed to manufacture W-phase type platelike ferrite particles having improved coercive force and squareness ratio. When the particles are used as magnetic particles for a magnetic recording medium, high-density magnetic recording can be attained while using a coated tape having high productivity. Since each of the particles has its axis of easy magnetization in a direction perpendicular to the platelike surface, the particles are made suitable for a vertical magnetic recording system by magnetic orientation. |
