| 简介 |
PROBLEM TO BE SOLVED : To provide a rare earth permanent magnet, high in performance and small in volume, which can be applied to a vibrating motor for a cellular phone and a high output and micro actuator required to a micro robot or a micro motor for internal body diagnosis.
SOLUTION : The Nd-Fe-B based sintering permanent magnet for a micro product shaped in cylinder or disk is characterized in that it has punctured internal surface which is formed by grinding sitering permanent magnet block raw material, in that a ratio of front surface area/volume is 3 mm-1 or more, and the volume is 20 mm3 or less simultaneously, in that (BH)max is recovered to 280 kJ/m3 or more by refining deterioration damage portion at grinding, and in that the refining is performed by displacing an Nd element of Nd2Fe14B main phase with R metal in such a way that the R metal (where, R is one kind or two kinds or more of rare earth elements selected from Nd, Dy, Pr, and Tb) is penetrated in spread inside the permanent magnet by a depth of 3 μm or more equivalent to a radius of crystal particle exposed to the most outer surface of the permanent magnet.
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