Two-dimensional van der Waals compounds with magnetic ions on a honeycomb lattice are hosts to a variety of exotic behavior. The magnetic interactions in one such compound, $\mathrm{Mn}\mathrm{P}{\mathrm{Se}}_3$, are investigated with elastic and inelastic neutron scattering. Magnetic excitations are observed in the magnetically ordered regime and persist to temperatures well above the ordering temperature, $T_{\text{N}}=74\mathrm{K}$, consistent with low dimensional magnetic interactions. The inelastic neutron scattering results allow a model spin Hamiltonian to be presented that includes dominant intralayer interactions of $J_{1ab}=0.45$ meV, $J_{2ab}=0.03$ meV, $J_{3ab}=0.19$ meV, consistent with theoretical predictions. Despite the quasi-2D behavior, appreciable interlayer interactions of $J_c=0.031\left(5\right)$ meV are required to model the data. No evidence for anisotropy in the form of a spin gap is observed in the data collected. The measurements on $\mathrm{Mn}\mathrm{P}{\mathrm{Se}}_3$ are contrasted with those on $\mathrm{Mn}\mathrm{P}{\mathrm{S}}_3$ and reveal a large increase in the interlayer exchange interaction in $\mathrm{Mn}\mathrm{P}{\mathrm{Se}}_3$ that may stabilize the similar ordering temperatures in the bulk compounds.

• Received 16 October 2020
• Accepted 21 December 2020

DOI:https://doi.org/10.1103/PhysRevB.103.024414