GRADIENT FUNCTIONALITY RARE EARTH PERMANENT MAGNET

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PROBLEM TO BE SOLVED : To provide a rare earth permanent magnet having a gradient function in which both high electric resistance and high magnetic characteristics are satisfied. SOLUTION : In a sintered magnet body containing RaEbTcAdFeOfMg composition obtained by making an R-Fe-B based sintered magnet body absorb E component and fluorine atom from its surface, F is distributed such that the concentration of component increases from the center toward the surface of the magnet body. At the grain boundary surrounding the main phase crystal grains consisting of tetragonal (R, E)2T14A in the sintered magnet body, concentration of E/(R+E) contained in the grain boundary is higher in average than that in the main phase crystal grains, an acid fluoride of (R, E) exists down to a depth region of at least 20 μm from the surface of the magnet body in the grain boundary, acid fluoride particles of 1 μm or above are distributed at a rate of 2, 000 /mm2 or more in that region, the acid fluoride occupies 1% or more in surface integral ratio, and eddy current loss characterizing that the electric resistance at the surface layer of the magnet body is higher than the internal electric resistance is reduced. COPYRIGHT : (C)2007, JPO&INPIT