Atomic-scale mechanisms of annealing-induced coercivity modification in metallic glass

Amorphous Fe₈₀Si₉B₁₁ ribbons were annealed at various temperatures below the crystallization temperature. Annealing-induced coercivity modification mechanisms at atomic scale in metallic glass were investigated by synchrotron X-ray diffraction. The peak intensity of the pair distribution function initially decreases before a sharp rise with the increasing annealing temperature. The peak positions move to large distances due to the enhanced thermal oscillations, then shift to short distances because of structural relaxation. Based on the synchrotron X-ray diffraction and Fe K-edge-extended X-ray absorption fine structure experiments, reverse Monte Carlo method was applied to extract the distribution of Fe-centered clusters. The variation of the distribution of Fe-centered clusters confirms the results from synchrotron X-ray diffraction. The thermal oscillations of the atoms lead to the relief of residual stress. Heating up to a temperature higher than 523 K reconstructs the distribution of internal stress and gives compressive stress an advantage. The variation of the distribution of atomic-scale hydrostatic stress upon annealing is responsible for the modification of the coercivity.