Spin and lattice dynamics of a van der Waals antiferromagnet MnPSe$_3$

TL;DR

This study investigates the spin and lattice dynamics of MnPSe3, revealing detailed magnon behavior and exchange interactions, while observing magnon-phonon band intersections without hybridization effects.

Contribution

The paper provides a comprehensive spin model for MnPSe3 based on inelastic neutron scattering, including detailed exchange parameters and anisotropy, and discusses magnon-phonon interactions.

Findings

Magnon bands are well characterized by a specific spin model.

Intersections of magnon and phonon bands observed without hybridization.

Exchange parameters and anisotropy constants are quantitatively determined.

Abstract

Antiferromagnetic van der Waals family $\rm \textit{M}P\textit{X}_{3}\ (M=Fe,\ Mn,\ Co,\text{ and}\ Ni; X=S\text{ and}\ Se)$ have attracted significant research attention due to the possibility of realizing long-range magnetic order down to the monolayer limit. Here, we perform inelastic neutron scattering measurements on single crystal samples of MnPSe$_3$, a member of the $\rm \textit{M}P\textit{X}_{3}$ family, to study the spin dynamics and determine the effective spin model. The excited magnon bands are well characterized by a spin model, which includes a Heisenberg term with three intraplane exchange parameters ($J_{1}=-0.73$~meV, $J_{2}=-0.014$~meV, $J_{3}=-0.43$~meV) and one interplane parameter ($J_{c}=-0.054$~meV), and an easy-plane single-ion anisotropy term ($D=-0.035$~meV). Additionally, we observe the intersection of the magnon and phonon bands but no anomalous spectral features induced by the formation of magnon-phonon hybrid excitations at the intersecting region. We discuss possible reasons for the absence of such hybrid excitations in MnPSe$_3$.