Theoretical spin-wave dispersions in the antiferromagnetic phase AF1 of MnWO${}_4$ based on the polar atomistic model in P2

Abstract

The spin wave dispersions of the low temperature antiferromagnetic phase (AF1) MnWO${}_4$ have been numerically calculated based on the recently reported non-collinear spin configuration with two different canting angles. A Heisenberg model with competing magnetic exchange couplings and single-ion anisotropy terms could properly describe the spin wave excitations, including the newly observed low-lying energy excitation mode ${\omega }_2$=0.45 meV appearing at the magnetic zone centre. The spin wave dispersion and intensities are highly sensitive to two differently aligned spin-canting sublattices in the AF1 model. Thus this study reinsures the otherwise hardly provable hidden polar character in MnWO${}_4$.

7 pages, 5 figures