Spin and lattice dynamics in the van der Waals antiferromagnet MnPSe

Liao, J.*; Huang, Z.*; Shangguan, Y.*; Zhang, B.*; Cheng, S.*; Xu, H.*; Kajimoto, Ryoichi  ; Kamazawa, Kazuya*; Bao, S.*; Wen, J.*

Antiferromagnetic van der Waals family P ( = Fe, Mn, Co, and Ni; = S 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, a member of the P 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 ( meV, meV, meV) and one interplane parameter ( meV), and an easy-plane single-ion anisotropy term ( 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.