PURPOSE: To obtain the magnetic powder excellent in dispersibility and saturation magnetization, reduced in temp. change of coercive force and electric resistance, and useful for magnetic recording material for high-density recording by applying specific treatment to a fine particles having magnetoplumbite-type crystalline structure.
CONSTITUTION: Fine particles composed of hexagonal magnetoplumbite-type ferrite represented, preferably, by a formula (where A means Ba, Sr, and Pb, M means Co, Ni, Zn, Cu, Bi, Ti, Zr, Sn, Nb, V, Mo, and W, and the symbols n, x, and α stand for 0.9-1.2, >0-<4, and -2-0, respectively) and having a magnetoplumbite-type crystalline structure in which particle size is regulated to ≤0.1μ are suspended in water. Subsequently, an aqueous solution containing ions of one or more metals selected from Co, Ni, Zn, and Cu and Fe2+ and aqueous alkali (e.g. NaOH) are added to the resulting suspension to form a mixed suspension, which is subjected to heating treatment at 50-200°C, washed, filtered, and then subjected to heat treatment at 100-500°C in a nonoxidizing atmosphere, such as N2.
HASHIMOTO KAZUO
FUJIMOTO TETSUYA
SATAKE AKIRA
