Magnetism of two-phase magnetic systems composed of nanograins embedded in an amorphous matrix

Soft magnetic nanocrystalline alloys have excellent soft magnetic behaviour that is interpreted as a consequence of the averaging out of the magnetocrystalline anisotropy of the ferromagnetic grains via the exchange magnetic interactions through the residual amorphous matrix. Thus, the macroscopic soft magnetic behaviour is basically determined by the structural and magnetic characteristics of the crystalline phase. However, the contribution of the amorphous matrix cannot be completely disregarded and under certain circumstances plays the dominant role in the magnetic behaviour of these exchange coupled systems. The magnetic hardening experimentally detected for low crystalline volume fractions and around the ferro-paramagnetic transition of the amorphous phase will be analyzed in terms of the reduction of the exchange transmission capability of the residual amorphous matrix. In particular, the magnetic transition associated with magnetic decoupling between the ferromagnetic crystallites around the Curie point of the residual amorphous phase, will be analyzed in deeper detail, i.e., the shift of the transition above the Curie point of the residual amorphous phase and the effect of the inclusion of metal transition impurities (Co, Cr) in the magnetic decoupling phenomena.