| 简介 |
PROBLEM TO BE SOLVED : To provide ferromagnetic powder for a coated magnetic recording medium which allows forming a magnetic layer suitable for high density recording.
SOLUTION : The ferromagnetic powder for a coated magnetic recording medium is iron-based containing Co of more than 5 to 50 at.%, Al of 0.1 to 30 at.%, rare earth elements (including Y) of 0.1 to 10 at.%, a group 1a element of the periodic table less than 0.05 weight%, a group 2a element of the periodic table less than 0.1 weight% (including 0 weight%), and consists of flat needle-shaped grains each with a long axis of 0.01 to 0.40 μm in average length and an X-ray crystal grain diameter (Dx) of 50 to 250 angstroms, a short-axial cross section, which is taken along the direction perpendicular to the long axis, having a longer width and a shorter width, the ratio of which, a short axis aspect ratio, is substantially uniform in the direction of the long axis, measuring greater than 1, preferably greater than 1.5; the ratio (σs/Dx) of the saturated magnetic susceptibility (σs) and the X-ray crystal grain diameter (Dx) of the ferromagnetic powder being equal to or larger than 0.7.
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