Evolution of coercivity during the early stages of Fe80B20 crystallization

We report a study of the evolution of coercivity (H-c) in partially crystallized Fe80B20 samples with an increasing number of crystallites obtained in a controlled way into ferromagnetic amorphous matrix. These samples allow to test existing models for interaction of domain walls with defects since it is possible to change only the number density of crystallites without modifying their dimensions. We observe that the evolution of H-c is mainly related to the nucleation frequency of grains and quite independent from their internal structure. The observed behavior of H-c can be accounted for by considering the dependence of coercivity on the number density of pinning sites and by assuming a two-dimensional bending of the domain walls during their motion. Moreover our results indicate that the changes occurring to the intergranular phase during annealing do not appreciably affect coercivity in the partially crystallized samples.