| 摘要 |
PURPOSE:To obtain the title ferrite magnetic powder having high reproducibility of coercive force and high dispersibility by treating hexagonal ferrite magnetic powder to be used for magnetic recording contg. Fe and at least one kind of metal among Ba, Sr, and Pb as essential component, with a strongly acidic aq. soln. having a pH below a specified value. CONSTITUTION:Hexagonal ferrite magnetic powder to be used for magnetic recording contg. at least one kind of the above described metal as essential component and small amts. of several metals (Mg, Sc, Y, V, Ta, etc.) for the purpose of control of magnetic characteristics or other purposes is prepd. The magnetic powder is then treated by dipping in aq. soln. of HCl, HNO3, oxalic acid, etc. having <=3 pH, or by other process. The treated magnetic powder is washed with water, dried and heated, if necessary, at <=900 deg.C to remove residual trace amt. of acid by combustion and/or decomposition. As the result, dispersion of coercive force between lots of the obtd. hexagonal magnetic powder is extremely small, and the dispersibility is improved remarkably. Therefore, the saturation magnetic flux density (Bm) or luster of a magnetic tape produced therefrom is improved remarkably.
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