Creep-induced magnetic anisotropy and magnetostriction in a nanocrystalline Co based alloy

Co rich amorphous alloy (Vitrovac® 6025) ribbons have been current-annealed under a tensile stress of 500 MPa, applied along the ribbon axis. This results in a strong, creep-induced magnetic anisotropy with a hard ribbon axis, which increases as current density J increases. For high J, the magnetostriction constant showed a two component behavior as a function of measuring stress; one component for low stress (σ<100 MPa) and another one for high stress (σ>100 MPa). These results are interpreted in terms of structural relaxation (low J) and nanocrystallization (high J). Magnetostriction measurements appear as a very sensitive characterization tool.