Fig. 3: Microstructural and nano-scale compositional analysis of Fe-enriched soft magnetic ribbons.

TEM images of a as-spun, b L-CL (annealed at 698 K), c H-CL (annealed at 746 K) samples. Each sample features a low-resolution bright-field image with an inset of corresponding SAED patterns shown in respective (i) and a high-resolution bright-field STEM image with an inset of corresponding nanobeam electron diffraction shown in respective (ii). The TEM images reveal an amorphous structure in the as-spun sample and the formation of nano-scale α-Fe crystals within a residual amorphous matrix in the annealed samples. APT elemental maps highlight B (green), Cu (orange), P (pink), and Si (blue) for the distinct samples: d as-spun, e L-CL, f H-CL. These maps show a uniform elemental distribution in the as-spun sample (d), the formation of Cu-clusters, and the nucleation of nano-scale α-Fe crystals embedded in an amorphous matrix (e, f), with an increased volume fraction of these crystals in the H-CL sample (f). Line compositional profiles, computed along the sky-blue cylindrical region marked in the respective APT maps of the samples: g as-spun, h L-CL, i H-CL, demonstrate uniform composition in the as-spun sample, with Fe-enriched regions forming in the annealed samples. Error bars indicate the standard deviations of the counting statistics in each bin of the profiles.