154 CHAPTER 14. SOFT-MAGNETIC MATERIALSdue to structural relaxation, one has to destroy the domain pattern by means of an external
field during annealing. The beneficial influence of field annealing is shown in Fig. 14.2.6,
curve C. Stress release has led to the disappearance of the comparatively large coercivity,
whereas the field alignment of the local anisotropies induced by structural relaxation has
led to the enhanced remanence. One of the advantages of amorphous alloys is their high
electrical resistivity, which leads to low eddy-current losses up to very high frequencies.
It is interesting to compare the effect of magnetic annealing of amorphous alloys with
the thermomagnetic treatment of the Fe–Ni alloys discussed above. In both cases, anneal
ing causes changes due to atomic rearrangements. In the Fe–Ni alloys, the corresponding
atomic motions proceed by normal diffusion requiring temperatures higher than 450°C. The
structural rearrangements in the metastable amorphous alloys occur below 400°C. In both
cases, the main effect of the external field is to destroy the domain structure and to align
all local fields and hence all thermally induced anisotropies in one direction, that is, in the
direction of the external field.