METHOD FOR PREPARING RARE-EARTH PERMANENT MAGNET

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PURPOSE : A method for preparing a rare-earth permanent magnet is provided to improve a coercive force of a R-Fe-B based permanent magnet without reduction of a residual magnetic flux density. CONSTITUTION : A method for preparing a rare earth permanent magnet includes the steps of : heat-treating a sintered magnet body and powder at a temperature equal to or less than a sintering temperature of the sintered magnet body in vacuum or in an inert gas for 1 minute to 100 hours to absorb at least one or at least two of R2, R3, and R4 in the powder in positioning the powder containing at least one compound or at least two compounds selected from an oxide of R2, a fluoride of R3, and an oxyfluoride of R4 wherein each of R2, R3, and R4 is at least one element or at least two elements selected from rare earth elements including Sc and Y, T for the sintered magnet. The sintered magnet is composed of R1aTbBcMdOeCfNg. The R1 is at least one element or two elements selected from the rare earth elements including Sc and Y. The T is one element or two elements selected from Fe and Co. The M is at least one element or at least two elements selected from a group consisting of 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 to g represent atomic percents of an alloy and are in the range : 12= 12.5+(e+f+g)×0.67-c×0.11, on a surface of the sintered magnetic body. © KIPO 2008