Spin dynamics of YMnO3 studied via inelastic neutron scattering and the anisotropic Hubbard model

We have investigated the spin dynamics of YMnO3 by inelastic neutron scattering and determined the spin-wave dispersion at low temperature. The spin-wave dispersions at low temperature have been analyzed with a simple nearest-neighbor anisotropic Heisenberg model and also by an anisotropic Hubbard model. Best fits are obtained only in the strong-coupling limit (U∕t>∼15), with planar exchange energy J=4t2∕U≃2.4meV, and anisotropy terms Dz=Ux′−Uz′≃0.32meV and Dy=Ux′−Uy′≃0.033meV. We have shown that in the strong-coupling limit, the anisotropic Hubbard model maps into the anisotropic Heisenberg model.