The field‐annealing effect on magnetoimpedance of a zero magnetostrictive metallic glass

A commercially made metallic glass, VAC6030, was used for the magnetoimpedance (MI) measurement. Some samples were annealed at a temperature (Ta=340 °C) slightly below its Curie point, and cooled in a transverse or longitudinal field. The frequency of the probe current was from 10 kHz to 10 MHz. MI is defined as ΔR/R≡[R(0)/R(Hs)]−1 and ΔX/X≡[X(0)/X(Hs)]−1, where Hs is the saturating field along sample length, R is the resistance, and X is the reactance. At relatively low frequencies MI is mostly inductive, at relatively high frequencies it is resistive, and a crossover could be defined at a characteristic frequency f0. When the sample is in the as‐cast state, f0=890 kHz. If samples have been field annealed, f0 could be shifted either downward or upward; f0 becomes 30 kHz after a transverse anneal, and 8 MHz after a longitudinal anneal. The field annealing would also change the magnitudes of MI. In theory, if f