CURRENT ANNEALINGS AND MAGNETOIMPEDANCE IN CO-FE AMORPHOUS RIBBONS

Amorphous ribbons of composition (Co0.95Fe0.05)(100-x)Si0.4xB0.62x, wi th x = 25 and 30 were prepared by the melt-spinning technique. Current annealings at 600 mA were performed for annealing times between 15 s and 60 min. The magnetoimpedance response was investigated by submitti ng the ribbons to ac currents at frequencies in the 10-200 kHz range, with amplitudes between 1 and 15 mA (rms), and measuring their voltage response. The observed results show that a transverse anisotropy is i nduced by the thermal treatments, which can be evaluated by means of t he magnetoimpedance effect. Due to its lower Curie temperature, the x = 30 ribbons exhibited lower sensibility to the current annealings.