Influence of core current on magnetization processes in amorphous and nanocrystalline Fe 73.5Cu 1Nb 3Si 15.5B 7 ribbons

Abstract

The model for the influence of surface fields H p generated by the core currents has been employed for the investigation of the magnetization processes and the domain structure in an initially amorphous Fe 73.5Cu 1Nb 3Si 15.5B 7 ribbon which was successively annealed at selected temperatures T a up to 540 °C. The analysis of the dM/dt vs. F curves and the M-H loops showed that in the as-received state only a fraction of inner domains with magnetizations I nearly parallel with the ribbon axis (i.e. with small angles 〈δ〉 between I and ribbon axis) participate in magnetization process. The analysis of the effects of H p on the coercive field H c and the shift of the center C of the M-H loop shows that the annealing up to T a = 450 °C reduces the average strength of pinning 〈S u〉 of the domain walls whereas the angle 〈δ〉 changes only a little with T a. For T a ≥ 400 °C the maximum magnetization M m practically reaches the saturation magnetization M s ( 1.3 T) already in the magnetizing field H 0 = 100 A m −1 which indicates rather simple domain structure with I mostly along the ribbon axis. At T a = 450 °C H c reached its minimum value, probably associated with the formation of nano-sized Fe-Si particles. Further annealing ( T a > 450 °C) leads to rapid increase in both 〈 S u〉 and 〈δ〉, hence also in H, as already observed in the previous studies.