Temperature effect on the MI ratio of Co 68.15Fe 4.35Si 12.5B 15 amorphous wires

Abstract

Study of temperature effects on magneto impedance (MI) ratio in Co 68.15Fe 4.35Si 12.5B 15 amorphous wires is here studied. Amorphous wires of 130 μm in diameter were prepared by in-rotating-water quenching technique. During MI measurements as a function of temperature, a decrease of MI ratio has been observed as the number of temperature sweeps increased. These wires have been subjected to different temperature sweeps beginning in 80 K until 300 K and slowly increasing the range until 400 K in order to detect a critical temperature. Such critical temperature has been found close to 375 K. The decrease of MI ratio is due to thermal diffusion and a change of the energy of the amorphous state as a consequence of the fact that the amorphous state is a meta stable state. It is believed that, at that temperature, atom diffusion and stress annealing take place and the state moves to a low-energy state following a dynamics in which the time when the sample is subjected to diffusion is important.