Restructuring disorder: Transformation from the antiferromagnetic order in Fe2VSi to the ferromagnetic state in FeRuVSi by substitution of a non-magnetic element

TL;DR

This study demonstrates that substituting non-magnetic Ru for Fe in Fe2VSi prevents atomic disorder, restores ferromagnetic order, and enhances the potential for half-metallic ferromagnetism in Heusler alloys.

Contribution

It introduces a novel substitution strategy to suppress disorder and recover ferromagnetic order in Fe2VSi-based Heusler alloys, advancing the design of robust half-metallic ferromagnets.

Findings

Partial Fe substitution with Ru prevents anti-site disorder.

Restoration of ferromagnetic order in FeRuVSi.

Atomic disorder reduces spin polarization despite structural improvements.

Abstract

The delicate nature of the half-metallic ferromagnetic (HMF) property in Heusler alloys is often compromised by inherent structural disorder within the systems. Fe2VSi is a prime example, where such disorder prevents the realization of the theoretically proposed HMF state as the anti-site disorder leads to the formation of two anti-parallel magnetic lattices resulting in antiferromagnetic order. In this study, we propose an innovative and simple strategy to prevent this atomic disorder by replacing 50% of the magnetic element Fe by a large, isoelectronic, non-magnetic element, Ru. In this way, one of the magnetic sublattices of the antiferromagnetic lattice ceases to order while ferromagnetic order is restored, an essential criterion for exhibiting HMF properties. Through various experimental measurements and theoretical calculations, we have shown that such partial replacement of Fe by Ru prevents the cross-site substitution of V/Si sites and the system regains its ferromagnetic order. Our theoretical calculations suggest that a perfect structural arrangement in Fe and Ru would have restored the HMF property in FeRuVSi. However, the local atomic disorder of Fe and Ru was found to decrease the spin polarization value. The present work sheds light on the complex interplay between structural disorder and magnetic properties in Heusler alloys and provides insights for future design strategies in the pursuit of robust half-metallic ferromagnets.