Magnetic Symmetry and Antiferromagnetic Resonance in CoO

Abstract

The irreducible corepresentations of the Shubnikov (magnetic) space group of ordered CoO ($\frac{{C}_{c}2}{c}$) have been deduced, and the magnon symmetries at various points in the Brillouin zone have been investigated. The antiferromagnetic resonance frequencies in CoO have been determined experimentally to be at 216.0, 221.0, and 248.0 ${\mathrm{cm}}^{\ensuremath{-}1}$ (each \ifmmode\pm\else\textpm\fi{} 0.2%). These results are compared with the neutron-scattering results and postulated magnon dispersion relations of Sakurai, Buyers, Cowley, and Dolling. It is suggested that the exchange constants ${J}_{1}$ and ${J}_{2}$ are about one order of magnitude smaller than previously assumed.