Influence of Tensile Stress on the Surface Magneto-Optical Hysteresis Loops in Amorphous and (Nano)Crystalline Ribbons

The behavior of the surface magnetic anisotropy in the amorphous and (nano)crystalline ribbons is investigated using the magnetooptical (MO) methods. In this paper, the differential intensity MO method is extended by the specially designed sample holder suitable for applying the tensile stress in the ribbon axis. Measured surface hysteresis loops, represented as a function of tensile stress σ, offer an interesting insight into the magnetoelastic properties of the ribbon surface phases. These dependencies are studied and discussed in the case of the surface-crystallized Co₆₆Fe₄Si₁₅B₁₅ and the as-quenched amorphous Fe_77.5Si_7.5B₁₅ ribbons. It is shown that the response of the surface crystalline phases and the amorphous matrix on applied stress is significantly different. This is manifested by the changes in the value and sign of magnetostriction coefficient λ_s. Good agreement between the surface and bulk magnetostriction is obtained for the FeSiB ribbons that are amorphous in the volume as well as on the surface.