Direct evidence for cycloidal modulations in the thermal-fluctuation-stabilized spin spiral and skyrmion states of GaV4S8

White, J. S. and Butykai, Ádám and Cubitt, R. and Honecker, D. and Dewhurst, C. D. and Kiss, László Ferenc and Tsurkan, V. and Bordács, Sándor (2018) Direct evidence for cycloidal modulations in the thermal-fluctuation-stabilized spin spiral and skyrmion states of GaV4S8. PHYSICAL REVIEW B, 97 (2). ISSN 2469-9950

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Abstract

We report small-angle neutron scattering studies of the lacunar spinel GaV4S8, which reveal the long-wavelength magnetic states to be cycloidally modulated. This provides direct support for the formation of N´eel-type skyrmions recently claimed to exist in this compound. In striking contrast with all other bulk skyrmion host materials, upon cooling the modulated magnetic states transform into a ferromagnetic state. These results indicate all of the modulated states in GaV4S8, including the skyrmion state, gain their stability from thermal fluctuations, while at lower temperature the ferromagnetic state emerges in accord with the strong easy-axis magnetic anisotropy. In the vicinity of the transition between the ferromagnetic and modulated states, both a phase coexistence and a soliton-like state are also evidenced by our study.

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