Carbonate effects in single-crystalline YBa2Cu3O7-δ

Physical properties in the normal and superconducting states for ${\text{CO}}_{3}$ substituted ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ single crystals are reported. From resistivity measurements in the normal state, it is obtained that the samples of the similar carrier doping, which is estimated by the $c$-axis resistivity, show a different behavior in the $ab$-plane resistivity if they have different concentrations of the carbon. The peak effects of the magnetization, which correspond to the critical current density in field, decrease with the substitution. These results suggest that the substituted carbonate affects the metallicity and superconductivity of the CuO chain layer. The substitution also suppresses the carrier doping and shortens the $c$-axis length as seen in polycrystalline samples. Some attention to purity of ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ will be required because ${T}_{\text{c}}$ can exceed 90 K for even relatively highly substituted samples, ${\text{YBa}}_{2}{\text{Cu}}_{3\ensuremath{-}x}{({\text{CO}}_{3})}_{0.04}{\text{O}}_{7\ensuremath{-}y}$.