The spin waves in single crystals of the layered van der Waals antiferromagnet CoPS3 have been measured using inelastic neutron scattering. The data show four distinct spin wave branches with large (≳14 meV) energy gaps at the Brillouin zone center indicating significant anisotropy. The data were modelled using linear spin wave theory derived from a Heisenberg Hamiltonian. Exchange interactions up to the third nearest-neighbour in the layered planes were required to fit the data with ferromagnetic J1=−1.37 meV between first neighbours, antiferromagnetic J3=3.0 meV between third neighbours, and a very small J2=0.09 meV between second neighbours. A biaxial single-ion anisotropy was required, with a collinear term Dx=−0.77 meV for the axis parallel to the aligned moment direction and a coplanar term Dz=6.07 meV for an axis approximately normal to the layered crystal planes.
@article{arxiv.2212.06479,
title = {Spin wave spectra of single crystal CoPS$_3$},
author = {A. R. Wildes and B. Fåk and U. B. Hansen and M. Enderle and J. R. Stewart and L. Testa and H. M. Rønnow and C. Kim and Je-Geun Park},
journal= {arXiv preprint arXiv:2212.06479},
year = {2023}
}