Enhancement of coercivity for Nd-Fe-B thin films by the infiltration of Nd-Cu alloy cap layer

摘要

In order to understand the mechanism of coercivity (H_c) of Nd-Fe-B magnets,we have investigated the effect of thermal annealing treatment on Nd-Fe-B thin films with Nd-Cu alloy cap layers.A substantial enhancement of H_c from 19.0 kOe (1512 kAm~(-1)) to 26.1 kOe (2078 kAnT~(-1)) was obtained for the Nd-Fe-B/Nd_(36)Cu~(64)films after post-annealing at 400 °C.Through electron microscope observation,it was revealed that Nd and Cu enrichment is clearly observed in the grain boundary of the Nd-Fe-B layer,whereas the concentration of Fe was decreased there.These results suggest that the exchange coupling between Nd_Fe_(14)B grains is weakened by the infiltration of a non-magnetic element into the grain boundary after the optimum thermal annealing treatment.