CRYSTAL-FIELD EXCITATIONS AND SUPERCONDUCTIVITY IN ND1+XBA2-XCU3O7

The f-electron excitation spectra of Nd ions in superconducting NdBa 2Cu3O7 and semiconducting Nd 1.5Ba1.5Cu3O7 have been determined by inelastic neutron scattering. Transitions within the paramagnetic ground-state multiplet due to crystal-field splittings have been observed up to about 120 meV in these materials. The temperature dependence of the width of the low-lying transition at ∼21 meV shows significant differences in the superconducting and normal states. Adopting the CF level assignments for HoBa2Cu3O7, we rescaled the CF parameters to account for the larger radial wave functions of Nd3+ ions and obtained a level scheme for the Nd using the lowest 100 states of the f 3 configuration. The calculated level structures for REBa 2Cu3O7 (RE=Nd, Pr, Ho) are in good agreement with neutron and susceptibility measurements. Influence of superconducting ordering on crystal-field transitions in the Nd1+xBa 2-xCu3O7 system is also discussed.