Effect of oxygen depletion on the transport properties of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

We report measurements of the resistivity (ρ), thermoelectric power (TEP), and Hall coefficient (${\mathit{R}}_{\mathit{H}}$) of sintered ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ for a range of δ values and for temperatures up to 300 K. As δ is increased, ${\mathit{T}}_{\mathit{c}}$ increases slightly, reaching a maximum for δ close to 0.1, and the TEP changes sign from negative to positive, while ${\mathit{R}}_{\mathit{H}}$ is positive for all values of δ. At low values of δ there is a marked increase in the fluctuation conductivity, which we have analyzed in terms of Aslamazov-Larkin fluctuations to determine the out-of-plane correlation length ${\xi }_{\mathrm{\perp }}$(0). A corresponding analysis of specific-heat data enables us to deduce the in-plane correlation length as well. We discuss the strong dependence of the Hall number on temperature and δ.