The dynamics and critical properties of FePS3, an Ising-like twodimensional magnet on a honeycomb lattice

Abstract

The MPS3 compounds (M = transition metal) are a family of materials where the M2+ ions lie in planes forming a honeycomb lattice. The planes are weakly bound by van der Waals forces and, when the M2+ carries a magnetic moment, the materials are good approximations of two-dimensional (2D) antiferromagnets. The FePS3 compound is of particular interest as it is a rare example of an Ising-like 2D magnet with honeycomb symmetry [1]. We have performed experiments with neutron scattering to investigate the magnon dynamics on both a powder [2] and, more recently, on a single crystal. We have further made extensive measurements of the critical dynamics of the compound. We will present our results, showing the magnon dispersion surface and the magnitudes of the exchange interactions along with the scaling behaviour of the magnetization and the anisotropy. The results will be contrasted with a sister compound, MnPS3, which is a good example of a Heisenberg-like 2D magnet. We will also discuss the possibilities for tricritical points and quantum phase transitions in this compound.