RARE EARTH-TRANSITION METAL-NITROGEN BASED MAGNET FINE POWDER AND METHOD FOR MANUFACTURING THE SAME

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PROBLEM TO BE SOLVED : To provide : rare earth-transition metal-nitrogen based magnet fine powder improved in magnetic property and excellent in stability of oxidation resistance by finely pulverizing magnet powder within a particular particle size range thereby forming a solid phosphate coating film on the surface of the resultant powder; and a method for efficiently manufacturing such magnet fine powder by pulverizing magnet coarse powder under a particular device condition. SOLUTION : Rare earth-transition metal-nitrogen based magnet fine powder is manufactured by a reduction diffusion method, and comprises 23.0-25.0 mass% of rare earth elements and 3.0-3.6 mass% of N with the balance consisting of substantially transition metal elements. The rare earth-transition metal-nitrogen based magnet fine powder is prepared by finely pulverizing magnet alloy powder together with an organic medium containing phosphoric acid by use of a media mixing mill. The rare earth-transition metal-nitrogen based magnet fine powder has an average particle diameter (D50) of 1-2 μm, provided that the percentage of particles having a size of 1 μm or smaller is 20-48%, and has a phosphate coating film formed on its surface and including 1 mass% or less of P in terms of the element. COPYRIGHT : (C)2014, JPO&INPIT