Dynamic magnetization processes in magnetostrictive amorphous wires

We have performed the theoretical studies on the longitudinal dynamic magnetization process of magnetostrictive amorphous wires characterized by a large single Barkhausen jump (magnetic bistability) based on our previous experimental measurements on these wires. The domain structures of these wire samples consist of a single domain inner core with axial magnetization surrounded by the outer domain shell with the magnetization oriented perpendicular (lambda(s >)0) or circular (lambda(s)< 0) to the wire axis. In the present work we use the resultant magnetization vector M tilting theta angle to z axis to describe the sample's domain structures. In terms of solving the Landau-Lifshitz-Gilbert equation followed by M the analytical solution of the dimensionless axial component of the magnetization m(z)=M-Z/M-s has been obtained, and m(z)[t(H-0,f(e)),tau,gamma] is a function of the field amplitude H-0, field frequency f(e), and the samples' material parameters such as the damping constant tau and the gyromagnetic ratio gamma. The function m(z)[t(H-0,f(e)),tau,gamma] allows us to study the dynamic properties of the magnetization process of a wire sample. It has been found that the switching time t(s), the switching field H-sw, and the dynamic coercive field H-dc depend on a magnetic field and material parameters. We found that the parameter alpha=gamma tau/(1+tau(2)) related to the rate of M, rotating the direction of the effective field, plays an important role in the magnetization process. By fitting the experimental data to the theoretical magnetization curve the value of the damping constant tau of the magnetostrictive amorphous wires can be estimated.