Coercivity enhancement of rapidly solidified Nd–Fe–B magnet powders

A high coercivity of 2.6 T is achieved in melt-spun Nd–Fe–B isotropic magnet powders by the grain boundary diffusion process using Nd80Cu20 and Nd82Al18 alloys. δM measurements indicate that Nd2Fe14B nanocrystals are magnetically decoupled after the diffusion process. Transmission electron microscopy revealed that the exchange decoupling is due to the formation of a thin Nd-rich phase at the grain boundaries. The mechanism of the coercivity enhancement is discussed based on microstructure observations and micromagnetic simulations.