The relationship between the crystallization process and the soft magnetic properties of nanocrystalline Fe–M–B–Cu (M=Zr, Nb) alloy

Abstract

The relationship between the crystallization process and the soft magnetic properties of nanocrystalline Fe84Nb3.5Zr3.5B8Cu1 alloy has been studied by comparison with that of Fe73.5Si13.5B9Nb3Cu1 alloy. When the annealing temperature Ta is slightly above the crystallization temperature, high permeability can only be obtained for Fe–Nb–Zr–B–Cu after annealing for very short times. The Ta dependence of the coercive force of Fe–Nb–Zr–B–Cu cannot be explained by the change of the grain size of the bcc phase. The soft magnetic properties of Fe–Nb–Zr–B–Cu is dominated by not only the grain size but also the Curie temperature of the intergranular amorphous phase. It is concluded that the magnetic softness of Fe–Nb–Zr–B–Cu is related directly to the degree of the reduction in the apparent anisotropy, while that of Fe–Si–B–Nb–Cu is strongly affected by the Si content of the bcc phase.