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• Fe 84 Zr x B 16- x (x = 6, 8, and 10 at. %) alloys show pronounced β relaxation characteristic. • A positive correlation between the β relaxation and structural heterogeneity appears in Fe-based amorphous alloys. • With increased Zr/B ratio, β relaxation is easily activated and structure becomes more heterogeneous. • Alloys with easily activated β relaxation or more heterogeneous structure possess poor soft magnetic properties. Dynamic relaxation is an universal feature in amorphous alloys. However, few studies have been conducted on β relaxation of Fe-based amorphous alloys as most of them have insignificant β relaxation characteristics. In this work, the variation in β relaxation, structural heterogeneity, and soft magnetic properties are investigated in Fe-Zr-B amorphous alloys with pronounced β relaxation. β relaxation and structural heterogeneity are characterized by the ratio of β and α relaxation temperature (i.e., T β /T α) and correlation length, respectively. With the increase of Zr/B ratio, the value of T β /T α and the correlation length tend to decrease. Alloys with easily activated β relaxation or more heterogeneous structure possess poor soft magnetic properties, i.e., a significant reduction in saturation magnetic flux density and an increase in coercivity. [ABSTRACT FROM AUTHOR]

• The nanoscale structural heterogeneity and magnetic properties were analyzed by atomic force microscopy and Mössbauer spectroscopy. • The nanoscale structural heterogeneity of Fe 80 Si 9 B 11 amorphous alloy attenuates monotonically with a decrease in cooling rate. • The annihilation of flow units induces the enhancement in ferromagnetic exchange interaction and weakening of magnetic anisotropy. • The ameliorated magnetic properties with decreasing cooling rate can be attributed to the degeneration of nanoscale structural heterogeneity. Despite that the nanoscale structural heterogeneity of amorphous alloys has been confirmed by advanced experimental observations and theoretical simulations, the underlying link between the structural heterogeneity and magnetic properties remains poorly known. In this work, the effect of cooling rate on the nanoscale structural heterogeneity and magnetic properties of Fe 80 Si 9 B 11 amorphous ribbons (Fe-Si-BAR) was studied by atomic force microscopy and Mössbauer spectroscopy. The results show that the degeneration of nanoscale structural heterogeneity substantially induces an improvement in soft magnetic properties with decreasing cooling rate. Specifically, the volume fraction of flow units reduces significantly with the decrease of cooling rate, and some of the flow units annihilate and transform to the ideal elastic matrix. The structural densification and reduction of the number density of quasidislocation dipole result in an enhancement in ferromagnetic exchange interaction and weakening of magnetic anisotropy. Therefore, the saturation magnetic flux density increases and coercivity decreases with reducing cooling rate. Our results provide new insight into understanding the structural mechanism in the ameliorated magnetic properties of Fe-based amorphous alloys with decreasing cooling rate. [ABSTRACT FROM AUTHOR]

• 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]

Metallic glasses are structurally heterogeneous on the atomic and nano scales. However, few investigations have been conducted on how the structural heterogeneities in these two scales co-evolve during annealing. In this work, the atomic and nanoscale structural heterogeneity evolution accompanying the magnetic softness is systematically discussed based on the literature and our previous synchrotron X-ray diffraction and atomic force microscopy results. We revealed the co-evolution mechanism of structural heterogeneities on the atomic and nano scales during annealing via the insight of percolation theory from the point of view of the local five-fold symmetry of the clusters. The results indicate that the reduction of atomic-scale structural heterogeneity during annealing is accompanied by an increase in the degree of local five-fold symmetry of the clusters and an alteration in their connection patterns. As the local five-fold symmetry of clusters in Fe-based metallic glasses reaches the percolation threshold, the nanoscale liquid-like regions tend to transform into solid-like regions. The great degree of percolation causes the pronounced weakening of the nanoscale structural heterogeneity accompanying changes in the shape and number of the liquid-like regions. The reduction of the number of liquid-like regions causes a reduction in vertical anisotropy and magnetic softening due to a more uniform and less free volume within the sub-circular shaped liquid-like region. • The evolution of the atomic/nano scale structural heterogeneity and its relation to the magnetic softness was discussed • The co-evolution mechanism of structural heterogeneities on the atomic and nano scales during relaxation is revealed. • The shape of liquid-like regions tend to become nearly circular during relaxation contributing to magnetic softening. [ABSTRACT FROM AUTHOR]

• The relaxation-induced evolution of nanoscale structural heterogeneity is analyzed by atomic force microscopy in Fe 80 Si 9 B 11 metallic glass. • The degeneration of nanoscale structural heterogeneity induces the improvement of soft magnetic properties. • The soft magnetic properties can be optimized by selectively tailoring the intrinsic structural heterogeneity of Fe-based metallic glass. Despite the mesoscopic isotropic nature of metallic glasses, there is a certain degree of structural heterogeneity down to the nanoscale. However, how structural heterogeneity affects the magnetic properties is still unclear. In this work, the relaxation-induced structural heterogeneity and magnetic properties evolution of Fe 80 Si 9 B 11 metallic glass were investigated by atomic force microscopy (AFM) and Mössbauer spectroscopy. We revealed that the correlation-length of nanoscale heterogeneity relates closely with the ferromagnetic exchange interaction together with the magnetic anisotropy, providing experimental evidence of the intrinsic link between the nanoscale structural heterogeneity and magnetic properties for Fe-based metallic glasses. The degeneration of nanoscale structural heterogeneity induces the enhancement of the ferromagnetic exchange interaction and weakening of the magnetic anisotropy. Our results have a vital significance in understanding the structure-property relationship of metallic glass. [ABSTRACT FROM AUTHOR]