Dispersion of the Г 6 (1) -Г 6 (2) Nd crystal field excitation in Nd 2 CuO 4

We performed inelastic neutron scattering experiments to determine the dispersion of the Г 6 (1) -Г 6 (2) crystal field excitation in Nd2CuO4. Our results can be very well described within the random phase approximation model. This allows a direct determination of the exchange coupling constants between the Nd ions. The superexchange interactions mediated by the oxygen and copper-oxygen layers are determined to be significantly stronger than the in-plane exchange between the Nd ions.