Characterization of localized hole states in Pr1+xBa2-xCu3O6+y by nuclear magnetic resonance

We investigated the charge distribution in Pr1+xBa2-xCu3O6+y crystals at li quid-He temperature by means of (CU)-C-63.65 and Pr-141-NMR and nuclear qua drupole resonance. The electric-field gradients determined fur the differen t oxygen coordinations of Cu(1) on the chains confirm the model that the ho le states are localized in the O2p pi orbitals of the CuO2 planes. The inte nsity and line-shape analysis of the Cu(1) and Pr resonances in the oxygen doping series (x approximate to 0,y=0...1) and in the Pr/Ba solid-solution series (at y = 1) allows us to assign the Pr resonance to Pr at rare-earth (RE) sites. Therefore we can investigate the charge distribution in the CuO 2-Pr-CUO2 layers by crystal-field analysis of the Pr signal. To consistentl y describe our results with neutron-scattering data we propose that two Pr states are present in the RE layer, and ascribe them to Pr with and one wit hout a hole localized in the oxygen coordination shell. NMR detects only th e former, with a virtually nonmagnetic singlet ground state, while space-in tegral techniques are dominated by the latter, due to a quasidoublet ground state and antiferrotnagnetism of its Pr moments at low temperature.