Magnetic anisotropy and magnetic ordering of transition-metal phosphorus trisulfides

Abstract

Here, a magnetic model with an unprecedentedly large number of parameters was determined from firstprinciples calculations for transition-metal phosphorus trisulfides (TMPS 3 's), which reproduced the measured magnetic ground states of bulk TMPS 3 's. Our Monte Carlo simulations for the critical temperature, magnetic susceptibility, and specific heat of bulk and few-layer TMPS 3 's agree well with available experimental data and show that the antiferromagnetic order of FePS 3 and NiPS 3 persists down to monolayers. Remarkably, the orbital polarization, which was neglected in recent first-principles studies, dramatically enhances the magnetic anisotropy of FePS 3 by almost two orders of magnitude. A recent Raman study [K. Kim et al., Nat. Commun. 10, 345 (2019)] claimed that magnetic ordering is absent in monolayer NiPS 3 but simultaneously reported a strong two-magnon continuum; we show that the criterion used to judge magnetic ordering there is invalid in monolayer NiPS 3 , thus providing an understanding of the two seemingly contradictory experimental results. The rich predictions on the magnetic susceptibility and specific heat of few-layer FePS 3 and NiPS 3 await immediate experimental verifications.