Dzyaloshinskii-Moriya interactions, N\'eel skyrmions and V$_4$ magnetic clusters in multiferroic lacunar spinel GaV$_4$S$_8$

TL;DR

This study combines ab initio calculations and simulations to analyze the magnetic interactions in GaV4S8, revealing the quantum nature of its magnetism and the stability of Neel skyrmions influenced by electronic correlations.

Contribution

It provides a detailed ab initio analysis of Dzyaloshinskii-Moriya interactions and magnetic states in GaV4S8, linking quantum effects to skyrmion stability.

Findings

Distributed-moment state explains skyrmion stability

Electronic correlations significantly affect DMI values

Quantum nature of magnetism is crucial for magnetic phase understanding

Abstract

Using ab initio density functional theory with static mean-field correlations, we calculate the Heisenberg and Dzyaloshinskii-Moriya interactions (DMI) for an atomistic spin Hamiltonian for the lacunar spinel, GaV$_4$S$_8$. The parameters describing these interactions are used in atomistic spin dynamics and micromagnetic simulations. The magnetic properties of the lacunar spinel GaV$_4$S$_8$, a material well-known from experiment to host magnetic skyrmions of N\'eel character, are simulated with these ab initio calculated parameters. The Dzyaloshinskii-Moriya contribution to the micromagnetic energy is a sum of two Lifshitz invariants, supporting the formation of N\'eel skyrmions and its symmetry agrees with what is usually expected for $C_{3\nu}$-symmetric systems. The are several conclusions one may draw from this work. One concerns the quantum nature of the magnetism, where we show that the precise magnetic state of the V$_4$ cluster is crucial for understanding quantitatively the magnetic phase diagram. In particular we demonstrate that a distributed-moment state of each V$_4$ cluster explains well a variety of properties of GaV$_4$S$_8$, such as the band gap, observed Curie temperature and especially the stability of N\'eel skyrmions in the experimentally relevant temperature and magnetic-field range. In addition, we find that electronic correlations change visibly the calculated value of the DMI.