Nanoscale structural heterogeneity and magnetic properties of Fe-based amorphous alloys via Co and Ni additions.

• The nanoscale structural heterogeneity was analyzed by small-angle X-ray scattering and atomic force microscopy. • The microalloying of Co and Ni exhibits an opposite effect on the nanoscale structural heterogeneity. • The variation of mechanical behavior further proves the evolution of the nanoscale structural heterogeneity with Co and Ni substitution. • The evolution of magnetic properties induced by microalloying can be attributed to the variation of nanoscale structural heterogeneity. Nanoscale structural heterogeneity is a critical parameter for understanding the structure-property relationships in amorphous alloys. Herein, the small-angle X-ray scattering and atomic force microscopy were utilized to quantitatively investigate the nanoscale structural heterogeneity of the Fe 80- x M x Si 9 B 11 (M = Co and Ni; x = 0, 2, 4) amorphous alloys. The results show that the nanoscale structural heterogeneity of the amorphous alloys increases prominently with Ni substitution, but gradually decreases with the increase of Co content. Such evolution of structural heterogeneity was further verified by the changes in mechanical behavior. The microalloying of Ni can increase the plastic deformation ability and reduce the microhardness, whereas an opposite effect is found in the Co-doped alloys. Finally, Mössbauer spectroscopy reveals an enhancement in ferromagnetic exchange interaction and magnetic anisotropy with Co substitution, while the microalloying of Ni leads to a deteriorative result. Such variations in magnetic properties can be attributed to the evolution of nanoscale structural heterogeneity with Co and Ni additions. Our observation serves as a link between the nanoscale structural heterogeneity and magnetic properties, providing a new sight into understanding the structural origin of the changes in magnetic properties of Fe-based amorphous alloys. [ABSTRACT FROM AUTHOR]