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 degrees 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 (H-c) 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 H-c 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). (c) 2006 Elsevier B.V. All rights reserved.