Effect of minor Co additions on the crystallization and magnetic properties of Fe(Co)NbBCu alloys

The effect of partial replacement of Fe by Co (up to 8%) on thermal stability, structure and magnetic properties of FeNbBCu alloys has been explored in this paper. The results indicate that Co reduces the stability against crystallization of the amorphous alloy and stabilizes the nanocrystalline phase prior to the further precipitation of metastable boride phases. Transmission Mössbauer spectroscopy reveals differences in the hyperfine interactions between the alloys: Co raises the mean hyperfine field of the amorphous state and differences in the nanocrystalline bcc-Fe(Co) environments between the alloys occur depending on the amount of Co near-neighbors in the bcc-Fe structure. The addition of Co has also a notable effect on the magnetic properties of both amorphous and nanocrystalline alloys increasing the Curie temperature, which shows a linear dependence with the Co composition, and the saturation polarization.