CRYSTAL-FIELD PROPERTIES OF F-ELECTRON STATES IN HOBA2CU3O7, NDBA2CU3O7, PRBA2CU3O7

We present details of our predictions for the crystal-field-split levels in RBa2Cu3O7 compounds with R = Nd3+ (f3 4I9/2) and Pr3+ (f2 3H4) based on the previously reported crystal-field split energy levels of f(10)5I8 for Ho3+ in HoBa2Cu3O7. Our predictions of the overall distribution of crystal-field levels provide the framework for interpretation of inelastic neutron scattering spectra of NdBa2Cu3O7 and PrBa2Cu3O7. For NdBa2Cu3O7 the inelastic scattering peaks are clearly seen and can be well assigned in terms of the energy levels of f3 4I9/2 by a small re-scaling of the predicted crystal-field parameters to adjust the overall width of the calculated spectrum. In the case of PrBa2Cu3O7 several important inelastic scattering features, particularly the lowest energy ones, are so unusually broad and weak that it was difficult to identify them without predictions of this type. Enough features in the scattering spectra have now been assigned for us to obtain fitted values for the crystal-field parameters of Pr3+ and Nd3+ in RBa2Cu3O7. As tests of these new assignments we discuss predictions of the anisotropies of magnetic susceptibility and the thermodynamic functions for the paramagnetic phase of PrBa2Cu3O7. Finally, a primitive model for interactions between Pr3+ ions is used to give an initial interpretation of the saturation moment that has been reported for the antiferromagnetically ordered phase of PrBa2Cu3O7. We conclude that standard crystal-field theory correctly applied to the f2 configuration of the Pr3+ ions fully explains the unusual magnetic properties of PrBa2Cu3O7.