Effects of Co doping on the transport properties and superconductivity in CeFe(1-x)Co(x)AsO.

A series of CeFe(1-x)Co(x)AsO oxyarsenide compounds with Co doping on iron sites (x = 0-0.2) have been synthesized by a solid state reaction method. The effects of Co doping on the electrical transport properties and superconductivity were analyzed with a special emphasis on the analysis of thermopower. Undoped CeFeAsO shows an electrical resistivity anomaly at about 150 K, which was ascribed to a spin-density-wave (SDW) instability. This anomaly is suppressed and a superconducting transition occurs at T(c) = 3.2 K in CeFe(0.95)Co(0.05)AsO, the maximum superconducting transition temperature (T(c)) of 12.5 K is observed in CeFe(0.90)Co(0.10)AsO, and the thermopower is increased by the Co doping. As has been previously suggested, the emergence of superconductivity seems to be closely linked to the thermopower, and there is a close correlation between T(c) and the thermopower, both showing a similar dome-like doping dependence.