Macroscopic demagnetization of the sintered Nd-Fe-B magnets prepared by Tb grain boundary diffusion

Macroscopic demagnetization in sintered Nd-Fe-B magnets by Tb grain boundary diffusion (GBD) is investigated in comparison with non-GBD ones. Demagnetization curves, the coercivity distributions, Tb content, and magnetic fields of the magnets at various external fields (mu 0Hext) are analyzed. As mu 0Hext approaches coercivity of the GBD magnet, S-N poles form near the center, between and parallel to the original N-S poles, indicating the magnetization reversal near the center of the GBD magnet. This is distinguished from the non-GBD magnets where demagnetization occurs mainly in the pole surfaces. The mechanism for macroscopic demagnetization is discussed.