Magnetism and Néel skyrmion dynamics in GaV4S8−ySey

Abstract

We present an investigation of the influence of low levels of chemical substitution on the magnetic ground state and Néel skyrmion lattice (SkL) state in GaV 4 S 8-y Se y , where y = 0, 0.1, 7.9, and 8. Muon-spin spectroscopy (μSR) measurements on y = 0 and 0.1 materials reveal the magnetic ground state consists of microscopically coexisting incommensurate cycloidal and ferromagnetic environments, whereas chemical substitution leads to the growth of localized regions of increased spin density. μSR measurements of emergent low-frequency skyrmion dynamics show that the SkL exists under low levels of substitution at both ends of the series. Skyrmionic excitations persist to temperatures below the equilibrium SkL in substituted samples, suggesting the presence of skyrmion precursors over a wide range of temperatures.

Structure and magnetism of the skyrmion hosting family GaV4S8−ySey with low levels of substitutions between Holt1, Štefančič2, Ritter3 et al. 2020Phys. Rev. MaterialsSelf Cite5050View full textAdd to dashboardCite

“…Density functional theory results on substituted GaV 4 S 8−y Se y from Ref. [26] support the evidence for the alteration of exchange pathways based on substitution at different sites. These results are complementary to our previous studies [24] and highlight the progression of the ordered magnetism of the parent compounds towards the spin-glass-like state for compounds with 1 y 7.…”

“…The powder ac susceptibility phase diagrams shown in Ref. [26] for y = 0, 0.1, 7.9, and 8 contain features that can be associated with the skyrmion, cycloidal, and ferromagneticlike magnetic phases in these materials. The attribution of these features to magnetic phases in the substituted materials are supported by μ + SR measurements [26].…”

“…[26] for y = 0, 0.1, 7.9, and 8 contain features that can be associated with the skyrmion, cycloidal, and ferromagneticlike magnetic phases in these materials. The attribution of these features to magnetic phases in the substituted materials are supported by μ + SR measurements [26]. A comparison of the phase diagrams determined from ac susceptibility data for the two parent compounds would appear to suggest that for compositions of GaV 4 S 8−y Se y with 0 y < 0.2 and 7.8 < y 8 skyrmions lattices could be stabilized.…”

“…The extent of the skyrmion phase strongly depends on the orientation of applied magnetic field with respect to the crystallographic direction [6]. Muon spin rotation (μ + SR) measurements have shown that there are large differences in the magnetic ground states of GaV 4 S 8 and GaV 4 Se 8 , with GaV 4 Se 8 showing a peculiar increase in local magnetic fields with an increase of temperature [26,27].…”

Megahertz dynamics in skyrmion systems probed with muon-spin relaxation

“…However, only a handful of results have been reported where LF μSR is used to study the skyrmion lattice (SkL). Studied systems include Cu 2−x Zn x OSeO 3 [29] (which hosts Bloch skyrmions) and GaV 4 S 8−y Se y [30,31] (which hosts Néel skyrmions). Similar behavior is observed in these materials, with an enhanced and broadened peak in the muon-spin relaxation rate found at temperatures just below the critical temperature T c at those external magnetic fields that stabilize the SkL.…”