Low-energy magnetic dynamics of Nd-moments in Nd2CuO4

We have investigated the collective magnetic excitations of the Nd3+ ions i n Nd2CuO4 at temperatures below the Nd magnetic ordering. These excitations were measured on a single crystal, by inelastic neutron scattering, along the main directions of the Brillouin zone. It has been experimentally shown that the multiplicity for the modes along the AM line is higher than 2, wh ile a model with only Heisenberg interactions predict 2 fourfold degenerate modes. We discuss a more complete Hamiltonian for the dynamics of the Nd3 magnetic moments, introducing exchange coupling of pseudo-dipolar type. (C ) 1999 Elsevier Science B.V. All rights reserved.