Superconductivity at 11.3 K induced by cobalt doping in CeFeAsO

Pure phases of a new oxyarsenide superconductor of the nominal composition CeFe0.9Co0.1AsO were successfully synthesized by solid state reaction in sealed silica ampoules at 1180 ∘C. It crystallizes in the layered tetragonal ZrCuSiAs type structure (sp gp P 4 / n m m ) with lattice parameter of ‘ a ’ = 3.9918 ( 5 ) Å and ‘ c ’ = 8.603 ( 1 ) Å . A sharp superconducting transition is observed at 11.31 K ( ± 0.05 K ) with an upper critical field of 45.22 T at ambient pressure. The superconducting transition temperature is drastically lowered ( ∼ 4.5 , 4.9 K) on increasing the concentration ( x = 0.15 , 0.2) of cobalt.