Tuning magnetic properties, thermal stability and microstructure of NdFeB magnets with diffusing Pr-Zn films

Abstract

Grain boundary diffusion process (GBDP) serves as a promising approach in improving magnetic properties and thermal stability of NdFeB permanent magnets. Herein, non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported. The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated. Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m−1 to 1317.14 kA m−1 without any remanence reduction. Notably, the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio. The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment. The well-optimized rare earth-rich (RE-rich) grain boundary phases and high effective anisotropy field of (Nd,RE)2Fe14B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of NdFeB permanent magnets via GBDP treatment.