| 摘要 |
PURPOSE:To obtain a magnetic powder whose coercive force is controlled to an appropriate value, whose saturated magnetization amount is large and which can be used suitably for vertical magnetic recording and high-density recording by a method wherein a hexagonal-system ferrite magnetic powder is used as a nucleus and magnetite is applied to its surface. CONSTITUTION:A hexagonal-system ferrite magnetic powder is used as a nucleus, and magnetite is applied to its surface. For example, barium ferrite is dispersed in an aqueous solution where ferrous sulfate has been dissolved and this dispersed solution is poured into a reaction container equipped with a stirrer; while this solution is stirred continuously, the barium ferrite is dispersed and an alkaline aqueous solution of a prescribed quantity is added. This mixed solution is heated; and when it starts boiling, an aqueous solution of potassium nitrite as an oxidizing agent is dripped gradually thereon; after a prescribed quantity has been dripped, this reaction solution is kept at its boiling point for one hour while it is being stirred; magnetite is applied to the surface of a barium ferrite magnetic powder. This powder is rinsed sufficiently and then dried; a magnetite-applied barium ferrite magnetic powder is obtained. |
