Magnon dispersion in MnWO4

The four magnon branches in the antiferromagnetic ground state of MnWO4 wer e measured by inelastic neutron scattering for two directions. On the basis of a model including isotropic Heisenberg exchange and uniaxial anisotropy , analytical expressions were derived for the dispersion relations in the s pin-wave approximation using the Holstein-Primakoff and Bogoliubov transfor mations. By comparison between observed and calculated excitation energies, a very reliable determination of model parameters was possible. In the fra mework of this model, the spin deviations at absolute zero and the propagat ion vector slightly below the transition temperature are calculated.