Quantification of the anomalous crystallization and soft magnetic properties of Fe–Si–B–P–Cu (Nanomet) by isothermal calorimetry

Abstract

The present study aimed to quantify the anomalous crystallization and soft magnetic properties of Fe–Si–B–P–Cu (Nanomet) alloy by isothermal calorimetry. The isothermal crystallization had slow kinetics at temperatures below the peak temperature of the exothermic event. The inhomogeneous distribution of pre-existing nuclei in the amorphous structure led to the anomalous crystallization, and hence, to a nonlinear Avrami plot with lowered localized Avrami exponents, attributed to temperature dependent crystallization kinetics. To the best of our knowledge, the presence of pre-existing magnetic nuclei was experimentally confirmed for the first time using ultra-high sensitive magneto-thermo-gravimetry (MTG). This is otherwise challenging, if not impossible, with conventional structural diffraction techniques. The incremental saturation magnetization (Ms) revealed how the volume fraction of the nanocrystallites intrinsically depends on both the annealing temperature and dwell time, and the significant change in the coercivity (Hc) confirmed the vital role the homogenous nucleation growth process has in order to achieve excellent soft magnetic properties.