Unusual nanogranular systems

Abstract Melt-spun Co 66 Nb 9 Cu 1 Si 12 B 12 metallic glass ribbon ( T C ≈150 K) was used to produce a series of nanocrystalline samples differing in the volume content of the crystalline phase as well as the sizes of the crystallites. An analysis of the zero-field-cooled (ZFC) and field-cooled (ZF) dependences of magnetization showed that at low temperatures the samples displayed mictomagnetic (cluster spin-glass) behavior, whereas on increasing temperature a majority of the existing crystallites, beginning from those of the smaller sizes, gradually became superparamagnetic. These characteristics also showed that the existing dipolar interactions between the crystallites decreased the energy barrier for thermal relaxation. This effect was also well visible in the dependences of the temperature derivative of the difference of ZFC and FC magnetizations which reflected a distribution of the blocking temperatures of the crystallites.