Divergent effects of deep cryogenic treatment on the structure and soft magnetic properties of Fe-based metallic glasses

This study investigates the divergent effects of deep cryogenic treatment (DCT) on the structure and soft magnetic properties of two Fe-based metallic glasses (MGs), FeSiB and FeSiBCCr. Results show that DCT induces non-monotonic structural relaxation in both alloys, but their magnetic responses differ significantly. For FeSiB, coercivity ( H c ) decreases by 7.3% while permeability ( μ ) and saturation magnetization ( M s ) remain largely unchanged. In contrast, FeSiBCCr exhibits substantial improvements in both permeability (up 25% at 1 kHz) and saturation magnetization (up 9%, 164→178 emu/g), achieving synergistic property enhancement. Correlation analysis identifies average electronegativity as the key parameter governing changes in saturation magnetization, while mixing entropy and average atomic size difference primarily influence coercivity reduction. Mössbauer spectroscopy suggests that DCT is associated with the evolution of weakly magnetic local environments toward more magnetically ordered atomic configurations, which may contribute to the release of the initially suppressed magnetic moments. These findings elucidate the atomic-scale order modulation mechanism of DCT and provide preliminary indications for designing high-performance soft magnetic MGs through tailored compositions and post-processing.