Magnetic Excitations in the Multiferroic N\'eel-type Skyrmion Host GaV$_4$S$_8$

TL;DR

This study uses broadband microwave spectroscopy to explore magnetic excitations in GaV4S8, revealing unique skyrmion-related modes influenced by strong uniaxial anisotropy, expanding understanding of multiferroic skyrmion hosts.

Contribution

It provides the first detailed microwave spectral analysis of Néél-type skyrmions in GaV4S8, highlighting the effects of uniaxial anisotropy on spin excitations.

Findings

Identified characteristic microwave modes in different magnetic phases.

Observed field-dependent transformation of excitation spectra in skyrmion phase.

Compared excitation spectra with Bloch-type skyrmion materials, noting key differences.

Abstract

Broadband microwave spectroscopy has been performed on single-crystalline GaV$_4$S$_8$, which exhibits a complex magnetic phase diagram including cycloidal, N\'eel-type skyrmion lattice, as well as field-polarized ferromagnetic phases below 13 K. At zero and small magnetic fields two collective modes are found at 5 and 15 GHz, which are characteristic of the cycloidal state in this easy-axis magnet. In finite fields, entering the skyrmion lattice phase, the spectrum transforms into a multi-mode pattern with absorption peaks near 4, 8, and 15 GHz. The spin excitation spectra in GaV$_4$S$_8$ and their field dependencies are found to be in close relation to those observed in materials with Bloch-type skyrmions. Distinct differences arise from the strong uniaxial magnetic anisotropy of GaV4S8 not present in so-far known skyrmion hosts.