Large Barkhausen Effect and Matteucci Effect in Cold-Drawn Amorphous Magnetostrictive Wires

A reinforced large Barkhausen effect and a Matteucci effect were obtained by subjecting cold-drawn amorphous magnetostrictive wires (Fe77.5Si7.5B15, produced by Unitika) to annealing under tension. The sharpness and amplitude of the voltage pulses induced in a pickup coil were proportional to the value of H^*-H0, where H^* is the critical field of domain nucleation at flux reversal, and H0 is the critical field for domain-wall displacement. The value of H^*-H0 increased to about ten times the value of as-prepared wires. The Matteucci voltage was also increased in the tension-annealed cold-drawn wires. The critical length of wires showing the Barkhausen effect was reduced to about 20 mm (vs. 60 mm for as-prepared wires). Small-size rotation sensors can be realized using the new wires.