Annealing effects on the magnetization reversal and domain wall dynamics in bistable amorphous glass-covered microwires

We study the mechanism of domain wall depinning and propagation in Fe77.5Si7.5B15 amorphous glass-covered microwires. These samples are ferromagnetic and spontaneously present the striking property of magnetic bistability, with the magnetization reversal process characterized by a single giant Barkhausen jump. This process allows one to easily measure the velocity of a domain wall propagating along the sample as a function of applied magnetic field and temperature and thus determine the wall mobility and the influence of different damping mechanisms on the domain wall dynamics. A discussion on the effects of thermal treatment on the wall mobility is presented. Domain wall velocities of the order of 850 m s-1 are measured. The temperature dependence of the wall mobilities established at 300 and 77 K, for as-cast and annealed samples, clearly shows a damping mechanism arising from the structural relaxation mechanism and from domain wall/atomic defect interactions, the second one playing a major role in the dissipative dynamics of magnetization reversal through depinning and domain wall propagation in Fe77.5Si7.5B15 microwires