Magnetic 3d-4f coupling in REBa2Cu3O7-delta

We present specific heat and inelastic magnetic neutron scattering data on REBa2CU3O7-delta (RE = rare earth). Independent of the oxygen content drastic anomalies are observed in the temperature behaviour of the magnetic neutron scattering response. The quasielastic linewidth is nearly independent of temperature up to about 100 K and then increases linearly. Below T approximate to 100 K the quasielastic scattering changes continuously from Lorentzian to Gaussian character. Together with the systematic variation of the 4f ordering temperatures found by specific heat measurements this suggests an increase of an indirect 3d-4f coupling with decreasing atomic number of RE and could therefore also explain the anomalies in PrBa2CuO7-delta.