Impact of local arrangement of Fe and Ni on the phase stability and magnetocrystalline anisotropy in Fe-Ni-Al Heusler alloys

TL;DR

This study uses density functional calculations to explore how atomic arrangement and Ni substitution affect phase stability and magnetocrystalline anisotropy in Fe-Ni-Al Heusler alloys, revealing new insights for magnetic material design.

Contribution

It systematically analyzes the influence of atomic arrangement and Ni substitution on structural and magnetic properties, proposing new pathways for enhancing FeNi-based permanent magnets.

Findings

Ni-rich alloys tend to decompose into Fe2NiAl and FeNi phases.

Replacing Ni with Al alters ground state structure and increases MAE.

Predicted Fe2NiAl has nearly cubic structure with high uniaxial MAE.

Abstract

On the basis of density functional calculations, we report on a comprehensive study of the influences of atomic arrangement and Ni substitution for Al on the ground state structural and magnetic properties for Fe$_2$Ni$_{1+x}$Al$_{1-x}$ Heusler alloys. We discuss systematically the competition between five Heusler-type structures formed by shuffles of Fe and Ni atoms and their thermodynamic stability. All~Ni-rich Fe$_2$Ni$_{1+x}$Al$_{1-x}$ tend to decompose into a dual-phase mixture consisting of Fe$_2$NiAl and~FeNi. The~successive replacement of Ni by Al leads to a change of ground state structure and eventually an increase in magnetocrystalline anisotropy energy~(MAE). We predict for stoichiometric Fe$_2$NiAl a ground state structure with nearly cubic lattice parameters but alternating layers of Fe and Ni possessing an uniaxial MAE which is even larger than tetragonal L1$_0$-FeNi. This opens an alternative route for improving the phase stability and magnetic properties in FeNi-based permanent magnets.