Direct evidence for structural origin of stress-induced magnetic anisotropy in Fe–Si–B–Nb–Cu nanocrystalline alloys

The structural origin of magnetic anisotropy in Fe–Si–B–Nb–Cu alloys annealed under a tensile stress of 200 MPa is studied by transmission x-ray diffraction. The diffraction peak of the (310) plane, whose normal vector is parallel to the tensile direction (ribbon direction), appears at a lower angle than the one perpendicular to it by about 0.1°. This indicates that the spacing of the (310) plane normal to the tensile direction is about 0.2% larger than the one parallel to it. This is direct evidence for the structural origin of the stress-induced magnetic anisotropy of nanocrystalline soft magnetic alloys.