Isothermal Annealing and Magnetic Properties of Fe70.5Cr3Cu1Nb3Si13.5B9 Amorphous Alloys

A thorough study has been performed on FINEMET type of ribbons with nominal composition of Fe70.5Cr3Cu1Nb3Si13.5B9 synthesized by rapid solidification technique. X- ray diffraction studies have been performed to identify the phases and to determine the grain size using Scherrer’s formula. Grain size increased with increasing annealing time and annealing temperature when the amorphous ribbon is annealed close to the crystallization temperature. The soft magnetic properties of this nanocrystalline alloy annealed at 425-560°C for 1 to 60 minutes at regular interval are investigated. Annealing time has great influence on permeability. The permeability increases gradually from 1 to 25 minutes then decreases. Curie temperature of the amorphous sample was found to be 276°C, which increased to 292°C gradually with increasing annealing temperature up to 475°C and then decreases for further increases. The results of the experimental observations are explained on the basis of existing theories of nanocrystalline amorphous metallic ribbons.