| 摘要 |
PURPOSE:To provide a magnetic powder for magnetic recording medium composed of a hexagonal ferrite low in dissolution property of alkaline earth element and to provide a producing method therefor. CONSTITUTION:The magnetic powder for magnetic recording medium is the hexagonal ferrite expressed by a general formula AFe(12-X)MXO19. (In the formula. A is one kind selected from Ba, Sr and Ca, M is one or more kind selected from In, Al, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Nb, Sb and Ta and X is number of 1-2, 5. Subsequently the same.) And on the surface, sulfate of Ba, Sr or Ca is formed. And the producing method is constituted by mixing a starting material containing Fe2O3, M, AO and B2O3 so that ratio of AO is excess and after heating and melting, by rapidly cooling to form a amorphous body, by heat treating to deposit a substituted hexagonal ferrite and by treating with dilute sulfuric acid or aq. sulfate solution to form sulfate of Ba, Sr or Ca on the surface of the hexagonal ferrite. |
