Studies of chemical homogeneity and magnetic domain walls in Fe-based metallic glasses using small-angle neutron scattering

Abstract

Metallic glasses Fe₇₇B₂₃, Fe₈₂B₁₈, and Fe₈₁B_13.5Si_5.5 have been studied as a function of applied field and annealing condition using small‐angle neutron scattering (SANS). The data were taken at 300 K for momentum transfer q = 4πsinϑ/λ in the range 0.05–0.3 nm⁻¹. In zero field, all the samples produced similar patterns with intense isotropic SANS for q−1 which could be fitted with Guinier radii R_G∼40 nm. This SANS decreased rapidly in intensity with applied field. The change in SANS on annealing correlated directly with changes in bulk coercivity H_c and domain wall density seen in electron microscopy: For stress‐relieved Fe₈₂B₁₈ and Fe₈₁B_13.5Si_5.5, SANS and H_c decreased slightly, but they increased substantially in Fe₇₇B₂₃ after annealing. This scattering arises primarily from domain walls in accord with dynamical theory. The weak SANS for 0.1−1 suggest that the phase separation and chemical inhomogeneity in these glasses, both as‐cast and annealed, are limited.