INFLUENCE OF CORE CURRENT ON MAGNETIZATION PROCESSES IN AMORPHOUS ANDNANOCRYSTALLINE FE73.5CU1NB3SI15.5B7 RIBBONS

The model for the influence of surface fields H-p generated by the cor e currents has been employed for the investigation of the magnetizatio n processes and the domain structure in an initially amorphous Fe73.5C u1Nb3Si15.5B7 ribbon which was successively annealed at selected tempe ratures T-a up to 540 degrees C. The analysis of the dM/dt vs. H curve s and the M-H loops showed that in the as-received state only a fracti on of inner domains with magnetizations I nearly parallel with the rib bon axis (i.e. with small angles [delta] between I and ribbon axis) pa rticipate 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 lo op shows that the annealing up to T-a = 450 degrees C reduces the aver age strength of pinning [S-u] of the domain walls whereas the angle [d elta] changes only a little with T-a. For T-a greater than or equal to 400 degrees C the maximum magnetization M-m practically reaches the s aturation magnetization M-s (approximate to 1.3 T) already in the magn etizing field H-0 = 100 A m(-1) which indicates rather simple domain s tructure with I mostly along the ribbon axis. At T-a = 450 degrees C H -c reached its minimum value, probably associated with the formation o f nano-sized Fe-Si particles. Further annealing (T-a > 450 degrees C) leads to rapid increase in both [S-u] and [delta], hence also in H-c, as already observed in the previous studies. (C) 1997 Elsevier Science S.A.