Spin-waves in CsMnF3

The spin-wave dispersion relations were determined by neutron inelastic scattering for the high symmetry directions (0 0 ξ) and (ξ 0 0) in the hexagonal antiferromagnet CsMnF 3 . The observed data were satisfactorily fitted to a theoretical model with two nearest-neighbour exchange constants, J 12 = 0.134 ± 0.003 THz and J 23 = 0.094 ± 0.0105 THz, and with one second-nearest-neighbour exchange constant, J 35 = −0.0138 ± 0.003 THz. An effective anisotropy field of −2700 ± 900 Oe along the crystal c axis was also included in the model. This field constrains the spins to the basal plane of the crystal and calculations show that magnetic dipole–dipole interactions can account for its observed magnitude.