R-T-B BASED SINTERED MAGNET

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PROBLEM TO BE SOLVED : To provide an R-T-B based sintered magnet easy to machine even if main phase crystal grains are controlled to have a small average particle diameter. SOLUTION : An R-T-B based sintered magnet according to the present invention has : main phase crystal grains of an R-T-B based compound including as primary components, a rare earth element (R), at least one kind of iron group elements (T) including Fe, or Fe and Co as an essential element, and boron (B); and grain boundaries. The main phase crystal grains have an average particle diameter of 2.8 μm or less. Further, the R-T-B based sintered magnet has a N-rich phase higher than the main phase crystal grain in N atomic concentration at each grain boundary multipoint surrounded and formed by three or more main phase crystal grains. Of the number of such grain boundary multipoints in a cut section of the R-T-B based sintered magnet, the number of grain boundary multipoints having the N-rich phase accounts for 70% or more. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2018, JPO&INPIT