Stress-induced magnetic and structural anisotropy of nanocrystalline Fe-based alloys

The structural anisotropy of Fe–Si–B–Nb–Cu nanocrystalline alloys annealed under tensile stress was studied by x-ray diffraction techniques with transmission geometry. A clear difference was observed in the peak positions of the Fe–Si crystals under two different conditions: with the diffraction vector parallel or perpendicular to the applied stress. The strains calculated from the anisotropy of the peak positions show a linear response to the applied stress, independent of Si content, indicating that the observed structural anisotropy is due to a quenching of the elastic strain, not in the directional ordering of the Fe–Si pair. The induced magnetic anisotropy energy is well explained by the residual strains and their magnetostrictions.