| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide hexagonal magnetoplumbite type ferrite having small average plate size, an adequate coefficient of variation of the plate size, an adequate ratio of the plate size to the plate thickness and adequate coercive force, to provide a method for manufacturing the hexagonal magnetoplumbite type ferrite and to provide a magnetic recording medium in which the hexagonal magnetoplumbite type ferrite is used in a magnetic layer and which shows high short-wavelength output and low medium noise when reproduced by using an MR head. <P>SOLUTION: The hexagonal magnetoplumbite type ferrite, which has 10-30 nm average plate size, 5-25% coefficient of variation of the plate size, 1.5-4.5 ratio of the plate size to the plate thickness and 125-400 kA/m coercive force, is obtained by forming a coprecipitated matter of a desired hexagonal magnetoplumbite type ferrite composition by a reverse micelle method, coating the surface of the coprecipitated matter with an alkaline-earth metal compound, heating the coated coprecipitated matter in the air at 550-650°C, subsequently heating the heated coprecipitated matter at 650-900°C to obtain ferrite and cleaning the obtained ferrite. The magnetic recording medium is obtained by incorporating the hexagonal magnetoplumbite type ferrite in the magnetic layer as magnetic powder. <P>COPYRIGHT: (C)2007,JPO&INPIT |
