Nd-Fe-B焼結磁石の界面構造と局所結晶場

概要

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The phase boundary between tetragonal Nd_2Fe_<14>B phase and fcc Nd-rich phase in Nd-Fe-B sintered magnets was investigated with a high-resolution transmission electron microscope. Two types of crystallographic orientation relationships were detected between two phases in direct contact; (110)_<tetra.> // (110)_<fc> , [001]_<tetra.> // [223]_<fcc> and (110)_<tetra.> // (010)_<fcc> , [001]_<tetra.> // [102]_<fcc>. The atomic structure of the phase boundary, based on the coincidence site lattice model, was modeled, and agreed with the observed relationships. The effective anisotropic coefficient K_<eff> at the Nd sites near the boundary was calculated to be 2.72 × 10^6 J/m^3 by using the point charge model when no account was taken of the Nd-rich phase. K_<eff> increases to 4.37 × 10^6 J/m^3 when the point charge of Nd^<3+> in the Nd-rich phase is taken into account, since the positive charge of the cation enhances the magnetocrystalline anisotropy near the boundary, where the nucleation of the reverse domain may be suppressed.
社団法人日本磁気学会の論文
2002-10-01