Local magnetic structure in fully and partially ordered V$_2$$X$Al Heusler alloys ($X$=Cr, Mn, Fe, Co, Ni)

Abstract

Multicomponent Heusler alloys exhibit various magnetic properties arising from their diverse atomic compositions and crystal structures. Identifying the general physical principles that govern these behaviors is essential for advancing their potential in spintronic applications. In this work, we combine density functional theory with atomistic Monte Carlo simulations to investigate the magnetic ground states, finite-temperature magnetic transitions, and electronic structures of fully-ordered $L2_1$-, $XA$-type, and partially-ordered V$_2X$Al ($X=$ Cr, Mn, Fe, Co, Ni) Heusler alloys. We propose the concept of magnetic motifs, defined as V-$X$-V triangular pathway connected by the nearest-neighbor (NN) exchange interactions $J_{\mathrm{V-}X}$. Within this framework, the magnetic ground states and transition temperatures across the V$_2X$Al family can be consistently understood. The magnetic order is primarily governed by the NN $J_{\mathrm{V-}X}$ interactions in the triangular motifs, while the transition temperatures are additionally influenced by $J_{X-X}$ couplings. Furthermore, the magnetic motifs are still proven to be effective in our calculations on partially-ordered V$_2$$X$Al alloys from $L2_1$ to $XA$-type structures. Our results suggest that the concept of magnetic motifs provides a unifying principle for understanding magnetic ordering in V-based Heusler alloys and could serve as a candidate guide for exploring magnetism and designing advanced spintronic materials in a broader class of Heusler systems.