Surface and bulk magnetic anisotropy in amorphous alloys

摘要

Magnetic measurements of hysteresis loops and transverse susceptibilities have been done on as‐cast iron based amorphous alloys on the surface and in the bulk of the ribbons. Bitter technique has been used to obtain the domain patterns. a‐Fe78B13Si9 shows an anisotropy perpendicular to the ribbon plane with maze domain ‘‘island’’ structures. The surface measurements do not detect any difference in behavior compared to the observed bulk properties. a‐Fe81.5B14.5Si4 shows different behavior in the surface and in the bulk of the ribbon with a perminvar‐type hysteresis loop from the surface and magnetization perpendicular to the ribbon plane with well‐aligned closure domains. The analysis of the different magnetic experimental data and selective changes in the internal stresses produced by different treatments support a model of the layered character of the anisotropies in this sample with tensile stresses and in‐plane anisotropy in the surface and compressive stresses and anisotropy perpendicular to the ribbon’s surface in the bulk. Finally, a rough calculation shows that the thickness of the surface in‐plane anisotropy region is of the order of the surface roughness.