Magnetic phases of skyrmion-hosting GaV$_4$S$_{8-y}$Se$_{y}$ ($y = 0, 2, 4, 8$) probed with muon spectroscopy

TL;DR

This study uses muon-spin spectroscopy to explore magnetic phases in GaV$_4$S$_{8-y}$Se$_{y}$, revealing distinct ground states, glassy behavior in intermediate compositions, and skyrmion lattice phases in specific materials.

Contribution

It provides new insights into the magnetic ground states and skyrmion phases of GaV$_4$S$_{8-y}$Se$_{y}$ using muon spectroscopy, highlighting differences between polycrystalline and single-crystal behaviors.

Findings

GaV$_4$Se$_{8}$ and GaV$_4$S$_{8}$ have distinct magnetic ground states.

Intermediate compositions show glassy magnetic behavior at low temperatures.

Skyrmion lattice phase observed in $y=0$ and 8 materials, with a smaller phase region in polycrystals.

Abstract

We present the results of a muon-spin spectroscopy investigation of GaV$_4$S$_{8-y}$Se$_{y}$ with $y=0, 2, 4$ and 8. Zero-field measurements suggest that GaV$_{4}$Se$_{8}$ and GaV$_{4}$S$_{8}$ have distinct magnetic ground states, with the latter material showing an anomalous temperature-dependence of the local magnetic field. It is not possible to evolve the magnetic state continuously between these two systems, with the intermediate $y=2$ and $4$ materials showing glassy magnetic behaviour at low temperature. The skyrmion lattice (SkL) phase is evident in the $y=0$ and 8 materials through an enhanced response of the muon-spin relaxation to the emergent dynamics that accompany the SkL. For our polycrystalline samples of GaV$_4$Se$_{8}$, this enhanced dynamic response is confined to a smaller region of the magnetic field-temperature phase diagram than the previous reports of the SkL in single crystals.