Effects of annealing time on nanoscale structural heterogeneity and magnetic properties of Fe₈₀Si₉B₁₀Cu₁ amorphous alloy

Abstract

The evolution of nanoscale structural heterogeneity and its effect on magnetic properties of Fe₈₀Si₉B₁₀Cu₁ amorphous alloy during structural relaxation after being annealed for different times are investigated in this work. The nanoscale structural heterogeneity is found to degenerate gradually with relaxation by using the small-angle X-ray scattering and atomic force microscope. Combined with Mössbauer spectroscopy analysis results, the enhanced comprehensive soft magnetic properties of the relaxed alloys can be attributed to the degeneration of nanoscale structural heterogeneity. From the flow unit model, the volume fraction of flow units decreases with relaxation proceeding, and some of the flow units annihilate and transform into the ideal elastic matrix. On the one hand, the relaxed sample with greater packing density has stronger magnetic exchange interaction and higher saturation magnetic flux intensity. On the other hand, the number density of quasi-dislocation dipoles decreases with the annihilation of flow units in the relaxation process, leading the pinning effect of the domain wall to be weakened. Consequently, the magnetic anisotropy decreases after relaxation, which results in the reduction of coercivity. In this work, the structural mechanism of the evolution of magnetic properties in the relaxation process of Fe₈₀Si₉B₁₀Cu₁ amorphous alloy is investigated from the perspective of structural heterogeneity, which is helpful in establishing the correlation between the structure and magnetic properties of Fe-based amorphous alloys.