Cu63NMR and hole depletion in the normal state of yttrium-richY1−xPrxBa2Cu3O7

The ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ Knight shift K and spin-lattice relaxation rate 1/${\mathit{T}}_1$ have been measured in the superconducting cuprate system ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Pr}}_{\mathit{x}}$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$, 0.05≤x≤0.20. With Pr doping K decreases and develops a temperature dependence at both plane and chain sites. This resembles the behavior of the Cu and Y Knight shifts as well as the bulk susceptibility in oxygen-deficient ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{y}}$. The orbital contribution to K and the anisotropy of the Cu hyperfine coupling remain essentially unchanged over the entire Pr concentration range. No appreciable direct effect of Pr magnetism on the conduction-band susceptibility was found. Instead, analysis of the bulk susceptibility and NMR data indicate that pair breaking and hole depletion both take part in the suppression of the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$. The temperature dependence of 1/${\mathit{T}}_1$ for magnetic field parallel to the c axis is also similar to that for the oxygen-deficient compound. 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.