EFFECTS OF CO, FE, AND AL DOPING ON THE OXYGEN DISORDERING AND SUPERCONDUCTING TRANSITION-TEMPERATURE OF YBA2CU3O6+X

Using computer simulation on a model of oxygen ordering in the basal Cu1-yMyOx plane of the high-temperature superconductor YBa2Cu3-yMyO6+x, we show that the effect of substituting Cu with M = Co, Fe, or Al is a diminishing of the oxygen-ordered orthorhombic domain sizes and eventually a breakdown of the orthorhombic structure. The model accounts for experimental structural data. By use of a previously established minimal model, which connects the superconducting transition temperature, T(c), to the formation of specific ordered orthorhombic domains in the undoped material, we show that the detrimental effect on T(c) by metal-ion doping as well as oxygen depletion becomes manifest in a unified way as a result of oxygen disordering.