Magnetic structure of polar magnet GaV$_4$Se$_8$ with N\'eel-type skyrmion lattice probed by $^{51}$V NMR

TL;DR

This study investigates the magnetic structure of GaV$_4$Se$_8$, revealing NMR signatures of various magnetic states and suggesting dynamic effects in the skyrmion lattice through $^{51}$V NMR measurements.

Contribution

It provides the first NMR analysis of the skyrmion lattice in GaV$_4$Se$_8$, highlighting domain-specific signals and the impact of skyrmion dynamics on NMR decay rates.

Findings

No NMR signal detected from the skyrmion lattice, indicating increased decay rates due to skyrmion dynamics.

Distinct NMR signals observed for cycloidal and conical magnetic states in different domains.

Magnetic cone structures close at the saturation field, leading to a single NMR peak.

Abstract

We report the magnetization and the $^{51}$V NMR measurements in the polar magnet GaV$_4$Se$_8$ in which a magnetic skyrmion lattice appears in the structural domain with the polar axis parallel to the magnetic field. Although we successfully separate the $^{51}$V NMR signals in the domain from those in the other structural domains, only the high-frequency region of NMR spectrum is observed due to a significant increase of the spin-echo decay rate in the low-frequency region. In $B_{\rm{ext}}\parallel[111]$, we find the NMR signals from the supermagnetized cycloidal state in the parallel domains as well as from the conical state in domains where the polar axis is tilted from the magnetic field. No NMR signal from the skyrmion lattice state is observed, suggesting a significant increase of the decay rate by additional low-energy excitations caused by dynamics of the skyrmions. In $B_{\rm{ext}}\parallel[001]$, where all the structural domains are magnetically equivalent, multiple NMR peaks converge into one peak at the saturation magnetic field. This field dependence is explained by the closing of magnetic cones as approaching the forced-ferromagnetic state.