ORIGIN OF TC SUPPRESSION AND MAGNETIC-ORDERING IN PRBA2CU3O7-DELTA

The magnetic 4f excitation spectrum of PrBa2Cu3O7-delta was measured by use of inelastic neutron scattering in a study of the ground-state properties of praseodymium. We analyzed the spectra in terms of crystal-field transition lines of a trivalent Pr ion. The absolute widths of the magnetic transition lines were found to be enhanced compared with those in stable R Ba2Cu3O7-delta compounds, where R is a rare-earth element. A distinct Absolute value of Q dependence of the inelastic magnetic intensities was found due to spatial magnetic correlations even above the unexpectedly high ordering temperature of the Pr magnetic moments. Both the enhanced width and the magnetic correlations are almost independent of the oxygen concentration. The enhanced widths indicate an increased hybridization between 4f electrons and electrons of the CuO2 planes. This is certainly responsible for the T(c) suppression in PrxY1-xBa2Cu3O7-delta, probably indirectly through the unexpectedly strong magnetic correlations (high ordering temperature) of the Pr magnetic moments caused by this enhanced hybridization.