DOMAIN-STRUCTURE, PINNING CENTERS AND MAGNETIZATION PROCESSES IN AMORPHOUS AND NANOCRYSTALLINE FE73.5CU1NB3SI15.5B7 RIBBON

A detailed analysis of the M-H loops and the corresponding dM/dH versu s H curves for a Fe73.5Cu1Nb3Si15.5B7 ribbon has been performed for di fferent stages of successive annealing (T-a less than or equal to 540 degrees C). The application of the model for the influence of the core current generated fields H-p on the process of magnetization of ferro magnetic ribbons showed that in the amorphous state (T-a less than or equal to 300 degrees C) only a fraction of the main (inner) domain str ucture participates in the process of magnetization. Further annealing strongly reduces the local anisotropy and the average pinning strengt h of the domain walls [S-u] which results in a very low coercive field H-c for 400 degrees C less than or equal to T-a less than or equal to 500 degrees C. Simultaneously, the maximum magnetization M-m becomes almost equal to the saturation magnetization M-s (approximate to 1.3 T ) already in low magnetizing field (H-0 = 100 A/m). The minimum of H-c (T-a = 450 degrees C) is associated with the formation of nanocrystal line Fe3Si grains. High M-m and maximum permeability mu(max) and a low angle [delta] (between the domain magnetizations and the ribbon axis) shows that the whole domain structure is very simple in this range of T-a. Further annealing (T-a > 500 degrees C) increases [S-u] and [del ta] (which increases H-c) and reduces drastically mu(max) which is con sistent with the earlier results for similar samples.