Effect of Cu Addition on Coercivity and Interfacial State of Nd-Fe-B/Nd-rich Thin Films

This study provides the effect of Cu addition on coercivity (H-cJ) and interfacial microstructure in Nd-Fe-B/Nd-rich thin films. All films were deposited by using ultra high vacuum (UHV) magnetron sputtering, and the Nd-Fe-B layer was oxidized under several atmospheres with different oxygen content. Then, the films were annealed at 250-550 degrees C under UHV. The films oxidized in low vacuum (10(-2)-10(-5) Pa) (under low oxygen state) exhibited the recovery of H-cJ by the annealing at 450 degrees C. On the contrary, the H-cJ of the films oxidized in Ar (under high oxygen state) decreased with increasing annealing temperature. However, the H-cJ increased drastically at the temperatures above 550 degrees C. In addition, the Cu added films, which were annealed at temperatures above 350 degrees C, showed higher coercivities than the films without Cu addition. The XRD analysis suggested the existence of C-Nd2O3 phase in the Cu added films annealed at 550 degrees C. It can be considered that the Cu addition decreases the eutectic temperature of Nd-rich phase and influences the interfacial state between Nd2Fe14B and Nd-rich phase.