Effect of the Si/B ratio on the magnetic anisotropy distribution of Fe73.5Si22.52xBxCu1Nb3 „x57,9,16… alloys along nanocrystallization

Abstract

The effect of the Si/B ratio on the magnetic anisotropy distribution of Fe73.5Si22.52xBxCu1Nb3 (x57,9,16) alloys has been studied. The influence of isochronal annealing on the hysteresis loop of the three studied alloys has been analyzed. They present two minima in coercivity: the first one can be ascribed to structural relaxation, and the second one is related to the averaging of the magnetocrystalline anisotropy, as predicted by the random anisotropy model. The relative importance of both minima changes with Si content: the lower the Si content, the more effective the structural relaxation and the less important the second minimum are. The mean value of the magnetic anisotropy distribution presents a similar behavior, evidencing the growing importance of the magnetoelastic anisotropy for the relaxed amorphous samples as the Si content is increased. From the evolution of the magnetic anisotropy distribution along nanocrystallization and the microstructural information obtained from transmission electron microscopy images, the behavior of the coercivity minima with changes in Si content can be ascribed to a different degree in compensation of magnetoelastic anisotropy due to the contributions of different signs coming from the nanocrystals and the amorphous matrix