Temperature activated magnetic relaxations in Co-based amorphous wires

Abstract Magnetic after effect (MAE) of Co-based amorphous wires is analysed in temperatures from 80 to 400 K for four main frequencies: 25, 50, 75 and 100 kHz and currents between 0.2 and 0.6 mA. Time evolution of the impedance after a sudden change from the axial applied field is recorded. Maxima in temperature are observed in the isochrones for some wires. Low-temperature annealing, far below Curie point, is responsible for the irreversible magnetic changes in the wire. Reorientation of atom pairs and redistribution of free volumes in successive temperature sweeps result in a change of the magneto impedance, and a stabilisation of the response. MAE also sets the precision of magneto impedance measurements and is an effective tool for checking temperature activated processes and stability of devices based on amorphous wires.