| 简介 |
A functionally graded rare earth permanent magnet having a reduced eddy current loss in the form of a sintered magnet body having a composition R a E b T c A d F e O f M g is obtained by causing E and fluorine atoms to be absorbed in a R-Fe-B sintered magnet body from its surface. F is distributed such that its concentration increases on the average from the center toward the surface of the magnet body, the concentration of E/(R+E) contained in grain boundaries surrounding primary phase grains of (R, E) 2 T 14 A tetragonal system is on the average higher than the concentration of E/(R+E) contained in the primary phase grains, the oxyfluoride of (R, E) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 µm, particles of the oxyfluoride having an equivalent circle diameter of at least 1 µm are distributed in the grain boundary region at a population of at least 2, 000 particles/mm 2 , the oxyfluoride is present in an area fraction of at least 1%. The magnet body includes a surface layer having a higher electric resistance than in the interior. In the permanent magnet, the generation of eddy current within a magnetic circuit is restrained. |
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