Theoretical study of magnetic properties and hyperfine interactions in $\sigma$-FeV alloys

TL;DR

This study uses electronic structure calculations to analyze magnetic moments and hyperfine interactions in $\sigma$-FeV alloys, comparing ferromagnetic and antiferromagnetic models to experimental data.

Contribution

It provides a detailed theoretical analysis of magnetic properties and hyperfine interactions in $\sigma$-FeV alloys, highlighting the importance of local magnetic configurations.

Findings

Hyperfine fields depend strongly on local magnetic arrangements.

Theoretical hyperfine fields for Fe overestimate, V underestimate experimental data.

Combining models reproduces the linear correlation between magnetic moments and hyperfine fields.

Abstract

Electronic structure Korringa-Kohn-Rostoker calculations for the $\sigma$-phase in Fe$_{100-x}$V$_x$ were performed in compositional range of its occurance ($\sim 34 \le x \le \sim 65$). Fe and V magnetic moments and hyperfine fields were determined for five inequivalent lattice sites in two models of magnetic structure, namely ferromagnetic FM and so-called anti-parallel one, APM, dominated by antiferromagnetic coupling. The average magnetic moments calculated for FM state overestimate the experimental data, whereas the corresponding quantities computed for APM state, underestimate them. Such a behavior remains in line with total energy values being similar for both models. The calculations showed that both average magnetic moments and hyperfine fields (on Fe and V atoms) vary with a number of Fe atoms in the nearest neighbor shell, $NN_{Fe}$, starting from critical values of $NN_{Fe}$, characteristic of each site. The calculated hyperfine fields for Fe and V showed an important role of valence contributions, being strongly dependent on local magnetic moments arrangements. In the case of Fe, the computed hyperfine fields are overestimated with respect to the Mossbauer data, while the corresponding values for V are underestimated with respect to the NMR results. However, the linear correlation between average magnetic moment and hyperfine fields, observed experimentally in FeV $\sigma$-phase, can be well reproduced when combining theoretical results for the two above-mentioned magnetic structure models.