Surface crystallization and frequency dependence of AC coercivity in Fe 80B 20 amorphous alloy

We report here, for the first time, the results of a study of the frequency dependence of coercivity ( H _c(ƒ) ) at the surface of amorphous and partially crystallized Fe ₈₀B ₂₀ samples with different degrees of crystallization. H _c(ƒ) 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(ƒ) ∝ ƒ ^α with α = 0.45 for the amorphous sample and α = 0.49 for the partially crystallized samples.