Spin wave excitations of Nd in Nd2CuO4

We performed inelastic-neutron-scattering experiments to determine the dispersion of the Nd spin wave excitations in $\rm Nd_2CuO_4$. The results were analysed with the help of a random phase approximation model calculation. We were able to find a set of exchange interactions that describes both the observed energies and the intensities of the excitations. Our result indicates that the interaction of the Nd spins is opposed to the ordering enforced by the Nd-Cu exchange. We argue that this will lead to an instability of the Nd ordering in the Ce-doped systems which might be important for the onset of high γ-values