Studies of structural and magnetic properties of glass-coated nanocrystalline Fe79Hf7B12Si2 microwires

In the present work we deal with the fabrication of thin of Fe79Hf7B12Si2 (low Si content) glass-coated microwire with a nanocrystalline structure and structural and coercivity characterization of such samples which can be considered as a new family of these nanocrystalline materials. Pieces of 10 cm of this microwire were annealed (300–600 °C during 1 h). The structural characteristics of the as-cast and annealed samples were determined, at room temperature, by X-ray diffraction (XRD) technique. XRD measurements allow to obtain the evolution of the grain size (15–35 nm) and relative volume fraction (5–60%) of the nanograins as a function of he annealing temperature in the annealed samples. Coercive field (Hc) of the as-cast and annealed samples has been evaluated from the hysteresis loop of the samples obtained by a conventional induction method at 100 Hz. Thermal dependence Hc is quite similar to that reported in other nanocrystalline Fe-based alloys. It slightly decreases from the as-cast state (relaxation process) showing small maximum at around 700 K (pre-nucleation of nanograins) decreasing significantly between 773–873 K (exchange coupling of the nanograins).