Quasi-Two-Dimensional Magnon Identification in Antiferromagnetic FePS3 via Magneto-Raman Spectroscopy

TL;DR

This study uses magneto-Raman spectroscopy to identify a magnon mode in FePS3, revealing its magnetic properties and behavior under temperature and magnetic field variations, advancing understanding of 2D antiferromagnetic materials.

Contribution

The paper demonstrates that a Raman-active mode previously thought to be a phonon is actually a magnon, providing new insights into FePS3's magnetic excitations and symmetry properties.

Findings

Identification of a 3.7 THz magnon mode in FePS3

Magnetic field and temperature dependence of the magnon

Determination of the g-factor as approximately 2

Abstract

Recently it was discovered that van der Waals-bonded magnetic materials retain long range magnetic ordering down to a single layer, opening many avenues in fundamental physics and potential applications of these fascinating materials. One such material is FePS3, a large spin (S=2) Mott insulator where the Fe atoms form a honeycomb lattice. In the bulk, FePS3 has been shown to be a quasi-two-dimensional-Ising antiferromagnet, with additional features in the Raman spectra emerging below the Neel temperature of approximately 120 K. Using magneto-Raman spectroscopy as an optical probe of magnetic structure, we show that one of these Raman-active modes in the magnetically ordered state is actually a magnon with a frequency of of approximately 3.7 THz (122 cm-1). Contrary to previous work, which interpreted this feature as a phonon, our Raman data shows the expected frequency shifting and splitting of the magnon as a function of temperature and magnetic field, respectively, where we determine the g-factor to be approximately 2. In addition, the symmetry behavior of the magnon is studied by polarization-dependent Raman spectroscopy and explained using the magnetic point group of FePS3.