INFLUENCE OF SURFACE-ROUGHNESS ON MAGNETIC-PROPERTIES OF FE-SI-B AMORPHOUS-ALLOYS

Influence of surface roughness on magnetic properties of Fe78Si9B13 an d Fe78Si14B8 amorphous alloy ribbons was investigated. Magnetic induct ion in an external field of 800A/m, B8 of Fe78Si9B13 ribbon increased slightly with decreasing surface roughness, while iron loss W13/50, at 1.3T 50Hz excitation, remained almost at the same level. In Fe78Si14B 8 amorphous alloy, however, quite different behaviors were observed. B oth B8 and W13/50 were improved remarkably with decreasing surface rou ghness of the ribbon. Fe78Si14B8 amorphous ribbon showed as good a mag netic performance as Fe78Si9B13 only if it had smooth surface. The dra stic improvement of iron loss with decreasing surface roughness was ma inly due to the decrease in hysteresis loss. According to the analysis of the iron loss and surface roughness of the ribbons, it was conside red that gentle and large undulations of the ribbon surface did not pr event domain wall from moving, but steep and small irregularities such as air pockets pinned domain wall. These behavior seems to be caused by the difference of mechanism of domain wall pinning in these two amo rphous alloys.