Direct evidence for cycloidal modulations in the thermal-fluctuation-stabilized spin spiral and skyrmion states of GaV 4 S 8

in Physical Review. B (2018), 97(2), 020401

We report small-angle neutron scattering studies of the lacunar spinelGaV4S8,which reveal the long-wavelength <br />magnetic phases to be cycloidally modulated. Upon cooling, these modulated phases ... [more ▼]

We report small-angle neutron scattering studies of the lacunar spinelGaV4S8,which reveal the long-wavelength <br />magnetic phases to be cycloidally modulated. Upon cooling, these modulated phases, including a recently <br />proposed Néel-type skyrmion phase, transform into a simple ferromagnetic state. These results indicate the <br />modulated phases in GaV4S8 gain their stability from thermal fluctuations, while at lower temperatures the <br />ferromagnetic state emerges in accord with the strong easy-axis magnetic anisotropy. Crucially, our study provides <br />microscopic evidence that the skyrmions in GaV4S8 indeed display a Néel-type helicity. More generally, our <br />approach can be applied to evidence the helicity of any bulk skyrmion phase. [less ▲]