Effect of Co Doping on the Superconducting Properties of Overdoped (Lu0.8Ca0.2)Ba2Cu3Oz

Abstract

The effect of Co-doping and thermal treatments on the superconducting properties of the heavily overdoped (Lu0.8Ca0.2)Ba2Cu3Oz has been investigated by X-ray diffraction, resistivity and thermoelectric power measurements. A comparative analysis of the resistivity and thermoelectric power of the (Lu0.8Ca0.2)Ba2(Cu3-xCox)Oz and the heat-treated Co-free (Lu0.8Ca0.2)Ba2Cu3Oz reveals that, in the overdoped region, the hole carriers reduced by the Co doping and by the oxygen depletion play a very similar role in the superconducting properties. As a result, a nearly common inverted parabolic correlation is observed between Tc and the planar carrier concentration determined from the room-temperature thermoelectric power measurements.