Effect of surface features of Fe-rich amorphous ribbons on the magnetic properties

The surface features of FE80.5(B,C,Si)19.5amorphous ribbons were measured by an optical method, and the permeability change by surface roughness and the relation between core loss and periodic surface roughness, which is called "fish scale", were investigated. The permeability decreased with increasing surface roughness and decreasing ribbon thickness. This deterioration, which is different from the changes by the residual stresses and the crystallization around air pockets, depended on the geometry of air pockets. The stronger fish scale with shorter pitch makes domain wall spacing smaller, and the eddy current loss decreases through the domain refinement. Domain wall spacing, 2L, was almost proportional to pt/(Rf+0.5), and eddy current loss, We, to pt²/(Rf+0.5), where t,p and Rf are ribbon thickness, the pitch of fish scale and the periodic roughness change of fish scale. So eddy current loss can be given by We α 2L.t The hysteresis loss increased as the surface roughness increased and the ribbon thickness decreased.