  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.
