SPIN-WAVE EXCITATIONS OF ND IN ND2CUO4

We performed inelastic-neutron-scattering experiments to determine the dispersion of the Nd spin wave excitations in Nd2CuO4. The results we re analysed with the help of a random phase approximation model calcul ation. We were able to find a set of exchange interactions that descri bes 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 wil l lead to an instability of the Nd ordering in the Ce-doped systems wh ich might be important for the onset of high gamma-values.