Temperature dependence of magnetization reversal in magnetostrictive glass-coated amorphous microwires

The temperature dependence of the magnetic behaviour of Fe-based glass-coated amorphous microwires with positive and large magnetostriction constant (around 30 ppm at room temperature) has been studied in the temperature range from 2 to 390 K. For long enough microwires (about 10 mm), hysteresis loops are squared shaped denoting the existence of a single domain structure and the magnetization reversal by a single Barkhausen jump. In the case of short microwires (around 2 mm) drastic changes are observed at low temperature where such magnetic bistability is lost. This is interpreted considering the influence of shape anisotropy: for short wires the demagnetizing field becomes large enough to destroy the single domain structure. On the other hand, the changing magnetoelastic anisotropy induced by coating when reducing measuring temperature is also considered. ular emphasis is additionally done to study the dependence of the switching field for magnetization reversal and that of its fluctuations on temperature and frequency of exciting field.