Reinforced Large Barkhausen and Matteucci Effects and Magnetoelastic Waves in Cold-Drawn and Then Torsion Annealed Amorphous Wires

The authors propose new methods for reinforcing the large Barkhausen and Matteucci effects in amorphous magnetostrictive wires. Cold-drawn and then torsion-annealed (CDTA) wires (Fe77.5Si7.5B15, 50 ¿m dia.) generate AC voltage pulses ep´ (Matteucci voltages) of between 35 and 75 mV across the ends of 200-mm long wires under 2 Oe, 60 Hz external fields. The critical wire length 1* for the large Barkhausen (LB) effect is about 25 mm, facilitating the construction of small-size field sensors. The critical field H* for the LB effect is 0.3 to 0.9 Oe. The value of ep´/l* for the CDTA wires is more than 200 times that of as-prepared 125 ¿m dia. wires. Magnetoelastic wave propagation characteristics are also remarkably improved in CDTA wires.