Quasi-two-dimensional magnon identification in antiferromagnetic FePS3 via magneto-Raman spectroscopy
Amber D. McCreary, Jeffrey R. Simpson, Thuc T. Mai, Robert D. McMichael, Jason E. Douglas, Nicholas P. Butch, Cindi L. Dennis, Rolando Valdes Aguilar, Angela R. Hight Walker
Recently it was discovered that van der Waals-bonded magnets retain long range magnetic ordering even down to a monolayer thickness, opening many avenues in fundamental physics and potential applications of these fascinating materials. One example is FePS3, a high spin (S=2) Mott insulator shown to be a quasi-2D-Ising antiferromagnet in bulk, where new features in the Raman spectra emerge below the Neel temperature of approximately 120 K. Through magneto-Raman spectroscopy, we will show that one of these Raman-active modes in the magnetically ordered state previously referred to as a phonon is instead a magnon with a high frequency of 3.6 THz (121 cm-1). We observe the expected temperature dependence and splitting of the magnon under applied magnetic fields, determining the g-factor to be ≈2. In addition, the symmetry behavior of the magnon, which is not antisymmetric, is studied and explained using the magnetic point group of FePS3.