Surface crystallization and frequency dependence of AC coercivity in Fe80B20 amorphous alloy

We report here, for the first time, the results of a study of the frequency dependence of coercivity (H-c(f)) at the surface of amorphous and partially crystallized Fe80B20 samples with different degrees of crystallization. H-c(f) shows a shape which does not depend on either the surface or bulk structure (i.e. crystalline or amorphous), consisting of a nearly constant value of H-c up to 100 Hz followed by a knee and a rapid increase as frequency is further increased. Our data are well fitted by a functional law H-c(f) proportional to f(alpha) with alpha = 0.45 for the amorphous sample and alpha = 0.49 for the partially crystallized samples. (C) 1998 Elsevier Science B.V. All rights reserved.