Magnetic penetration depth of Y1−xPrxBa2Cu3O6.97 measured by muon-spin relaxation

Abstract

We have measured the magnetic penetration depth of the high-${\mathit{T}}_{\mathit{c}}$ superconducting system ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Pr}}_{\mathit{x}}$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.97}$ for 0.05≤x≤0.4 using the technique of transverse-field muon-spin relaxation. The temperature dependence is similar to that of the related compounds ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ with varying oxygen content. The zero-temperature relaxation rate and ${\mathit{T}}_{\mathit{c}}$ both decrease monotonically with x, in a manner similar to those of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ with increasing δ. This observation is consistent with the interpretation that Pr is nearly tetravalent in this system so that ${\mathit{T}}_{\mathit{c}}$ is largely suppressed by means of the filling of holes in the conducting ${\mathrm{CuO}}_2$ planes. The influence of pair breaking, finite mean free path, and correlation with results for other high-${\mathit{T}}_{\mathit{c}}$ superconductors are discussed.