FUNCTIONALLY GRADED RARE EARTH PERMANENT MAGNET

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PURPOSE : A functionally graded rare earth element is provided to efficiently enhance heat resistance by having magnetic structure that the coercivity of a surface layer of a magnet body is higher than that of the inside of the magnet body. CONSTITUTION : A functionally graded rare earth permanent magnet is a sintered magnet body having a composition of R1aR2aTcAdFeOfMg. R1 is one or two kinds selected from rare earth elements including Sc and Y and excluding Tb and Dy, R2 is one or two kinds selected from the Tb and Dy, T is one or two kinds selected from Fe and Co, A is one or two kinds selected from B and C, M is one or two kinds selected from Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, and W, and a - g are atom percents of alloy in a range of 10<=a+b<=15, 3<=d<=15, 0.01<=e<=4, 0.04<=f<=4, 0.01<=g<=11 and c is a balance. In a grain boundary unit surrounding a columnar grain composed of a (R1, R2)2T14A tetragon, the concentration of R2/(R1+R2) included in a grain boundary is averagely denser than that of R2/(R1+R2) of the columnar grain. The R2 is distributed so that the concentration thereof gets denser from the center of the magnet body toward the surface of the magnet body. The acid fluoride of (R1, R2) exists in the grain boundary unit to a depth of at least 20um from the surface of the magnet body of the grain boundary unit. A surface layer has higher coercivity than the inside of the magnet body. © KIPO 2006