MAGNETIC POWDER FOR COATING TYPE MAGNETIC RECORDING MEDIUM COPING WITH HIGH-DENSIFICATION AND MANUFA

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PROBLEM TO BE SOLVED : To overcome the problem in the magnetic powder for coating type magnetic recording medium that the variety of the size and shape of particles is increased and, further, the particles at fine grain side of a particle size distribution become not to have magnetism by the fluctuation of heat or super para and, as a result, an SFD is deteriorated when it is seen as a whole powder body when the particle volume of the magnetic particle is decreased corresponding to a short wavelength record in magnetic powder for coating type magnetic recording medium. SOLUTION : Needle type particles having a principal constituent of Fe containing Co, Al, R (R shows at least one kind of rare earth element containing Y) are constituted of needle particles having the average major axis length L of the particles L=10-80 nm, the average minor axis length D of the particles D=2-20 nm, the axial ratio L/D of the particles L/D=1.5-8. the major axis lengths distribution (reference deviation/average value×100)σL=≤25%, the minor axis lengths distribution of the particles (reference deviation/average value×100)σD≤25%, the crystallite (grain size of crystal) of particles Dx=50-160 Å, while the existing ratio of the super fine particles of 1 nm-10 nm with respect to the whole particles of the fine particle magnetic powder for the coating type magnetic recording medium is less than 15%. COPYRIGHT : (C)2006, JPO&NCIPI