The coercivity dependence of giant magneto-impedance effect in Fe–Cu–Nb–Si–B based metallic alloy ribbon at different crystalline stages

Abstract We have studied the giant magneto-impedance (GMI) effect in one Fe-based FINEMET alloy ribbon with nominal composition Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 (at %). DTA experiments were conducted to identify the primary and secondary crystallization temperatures. XRD, SEM and EDAX were performed to identify the phases at various crystalline stages. Static magnetic properties of the ribbons were measured using a VSM. Coercivity was found to be a strong function of annealing temperature, and this, in turn depended on the size and type of the crystalline phases. The maximum MI effect of 103.4% was observed at annealing temperature of 600°C. It was found that a small change in DC coercivity as a result of annealing greatly changed the MI ratios of the crystalline ribbons. Annealing above the secondary crystallization temperature caused the precipitation of Fe 2 B and Fe 3 B phases, which induced magnetic hardening and eliminates MI sensitivity.