Effect of HCl on the normal magnetic susceptibility of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

Normal static magnetic-susceptibility measurements have been carried out for the high-$T_c$ superconductor ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ which was annealed at temperatures between 100 and 500 °C in the presence of HCl gas at a pressure of 100 Torr. The magnetic susceptibility data strongly depend on the change in the proportion of ${\mathrm{Cu}}^{2+}$ to ${\mathrm{Cu}}^{3+}$ during the reaction of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ with HCl. The Curie-Weiss susceptibility arises from the localized ${\mathrm{Cu}}^{2+}$ spins and the Pauli paramagnetic susceptibility arises from conduction electrons in ${\mathrm{Cu}}^{3+}$ states. These data can be interpreted in terms of the two-dimensional ordering of oxygen-vacancy sites in the one-dimensional chains in CuO layers. The one-dimensional chains have a stoichiometry of ${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}^{3+}$ ${\mathrm{Cu}}_{\mathit{x}}^{2+}$ ${\mathrm{O}}_{1\mathrm{-}\mathit{x}/2\mathrm{}}$ with δ=x/2.