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

Abstract

Metallic glasses Fe77B23, Fe82B18, and Fe81B13.5Si5.5 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<0.1 nm−1 which could be fitted with Guinier radii RG∼40 nm. This SANS decreased rapidly in intensity with applied field. The change in SANS on annealing correlated directly with changes in bulk coercivity Hc and domain wall density seen in electron microscopy: For stress-relieved Fe82B18 and Fe81B13.5Si5.5, SANS and Hc 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<q<0.3 nm−1 suggest that the phase separation and chemical inhomogeneity in these glasses, both as-cast and annealed, are limited.