Spin dynamics in the skyrmion-host lacunar spinel GaV4S8

TL;DR

This study investigates the spin excitations in GaV4S8, revealing the interactions that lead to its complex skyrmion phase through neutron scattering and spin-wave modeling.

Contribution

It provides the first detailed analysis of spin excitations in GaV4S8, clarifying the roles of ferromagnetic and Dzyaloshinskii-Moriya interactions in its skyrmion phase.

Findings

Identification of spin-wave excitations consistent with a cluster model

Confirmation of ferromagnetic and antisymmetric DM interactions

Support for molecular cluster interaction picture

Abstract

In the lacunar spinel GaV4S8, the interplay of spin, charge, and orbital degrees of freedom produces a rich phase diagram that includes an unusual Neel-type skyrmion phase composed of molecular spins. To provide insight into the interactions underlying this complex phase diagram, we study the spin excitations in GaV4S8 through inelastic neutron scattering measurements on polycrystalline and single-crystal samples. Using linear spin-wave theory, we describe the spin-wave excitations using a model where V4 clusters decorate an FCC lattice. The effective cluster model includes a ferromagnetic interaction and a weaker antisymmetric Dzyaloshinskii-Moriya (DM) interaction between the neighboring molecular spins. Our work clarifies the spin interactions in GaV4S8 and supports the picture of interacting molecular clusters.