Thermal analysis of nanostructured alloys obtained by Co-based amorphous ferromagnets

We are dealing with thermal and magnetic properties of nanostructured materials obtained by suitable thermal treatments of sort magnetic Co-based amorphous alloys of Metglas 2714A and Vitrovac 6025 below their conventional crystallization temperature. The ultrafine grain structures lead to superior soft magnetic properties: in homogeneously nanostructured samples of Metglas 2714A the average grain size giving the best soft magnetic properties is of about 2 nm, while in Vitrovac 6025 is about 10 nm. In soft nanostructured samples, structural and magnetic transitions are studied by means of differential thermal analysis, by thermogravimetry with low and non uniform magnetic field and by means of magnetization behavior as a function of the temperature. The results are compared with those of the precursor amorphous alloys and may be justified on the basis of the random anisotropy model generalized for two magnetic phase systems.