Interface nanostructure of Cu-added Nd-Fe-B sintered magnets processed by high magnetic fields

Akiya, Takahiro*; Kato, Hiroaki*; Takeda, Masayasu  ; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Sagawa, Masato*; Koyama, Keiichi*; Miyazaki, Terunobu*

Sintered Nd-Fe-B magnets consist of NdFeB main phase with about 5m diameter and Nd-rich grain boundary phase. It is well known that the coercivity of sintered Nd-Fe-B magnets is highly dominated by this Nd-rich phase, which is reported to change from discontinuous to continuous arrangement by a low temperature annealing around 500600C. We have shown that the coercivity of sintered Nd-Fe-B magnets can be further increased by applying a high magnetic field during the annealing. We found that such a coercivity enhancement phenomenon occurred only when a small amount of Cu is added, and when the annealing temperature is around 500C or 550C. In this paper, we report on the results of interface nanostructure analysis by DSC and Small Angle Neutron Scattering experiments to investigate the reason magnetic field effect occurs only in Cu-containing samples at specific annealing temperatures.