Temperature effects in Co-based amorphous wires

Abstract Irreversible temperature effects in the magneto impedance (MI) ratio of Co-based amorphous wires take place for temperatures below the Curie point. Results show that anisotropy changes are activated in a relatively low temperature range. As the temperature grows, [4] irreversible processes take place [A. Radkovskaya, A.A. Rakhmanov, N. Perov, P. Sheverdyaeva, A.S. Antonov, J. Magn. Magn. Mater. 249 (2002) 113] and the MI response is affected when the temperature sweep passes over 375 K as previously reported [O. Montero, V. Raposo, D. Garcia, H. Chiriac, J. Iniguez, J. Magn. Magn. Mater. 290–291 (2005) 1075]. Thermal stability for several Co-based compositions after several sweeps is studied when passing 375 K. Co-based samples are 12 cm long and diameters about 125 μ m . Cr and Mn are introduced in the compositions in order to observe different thermal behaviours. MI measurements were obtained with 1 mA of amplitude at four frequencies: 25, 50, 75 and 100 kHz for all wires. Magnetic after-effect (MAE) is also used to support the thermal activation of the irreversible processes.