AC loss analysis and domain structure in magnetostrictive amorphous wires

Abstract

Low-field ac susceptibilities of rotating water quenched amorphous Fe 77.5Si 7.5B 15 wires have been measured as functions of frequency and position. Anomalous eddy-current losses have been detected for different positions at the remanence state of samples with different lengths, related to the domain structures. An eddy-current loss model has been developed which combines the effects of magnetization rotations in a tubular shell, the displacements of a tubular domain wall in the core region, and the displacements of the shell-core boundary. Using this model, the ac losses have been analyzed, concluding that the radius of the boundary is 83% of the wire radius and the domain division makes a roughly parabolic axial position dependence of the average magnetization in the core, no matter if the wire is in the stable state or during magnetization reversal. Thus, the magnetization reversal should be controlled by domain wall pinning. In addition, magnetic relaxation and magnetomechanical coupling play important roles in the technical magnetization of such wires.