Copper NMR and role depletion in the normal state of Y1-x Prx Ba2 Cu3 O7

Normal-state copper NMR spectra and spin-lattice relaxation rates 1/T1 have been measured in the planar cuprate system Y1-x Prx Ba2 Cu3 O7. The Knight shift K decreases with Pr doping and develops a temperature dependence at chain sites. Analysis of the bulk susceptibility and NMR data indicates that pair breaking and hole depletion both take part in the suppression of the superconducting transition temperature Tc. The Knight shift behavior resembles that in oxygen-deficient YBa2 Cu3 O7-y, as does the temperature dependence of 1/T1 for plane Cu sites and magnetic field perpendicular to the c axis. This agreement leads to a consistent picture of the role of antiferromagnetic fluctuations in these materials. An analysis of the data in the framework of the phenomenological theory of Millis, Monien and Pines is given. In the end compound Pr Ba2 Cu3 O7 the NMR signal from plane Cu sites indicates antiferromagnetic (AF) ordering at a Neel temperature ∼ 280 K, and in the AF state yields the internal field similar to those found in AF YBa2 Cu3 O6 and La2 Cu O4. (author)