Superconductivity at 11.3 K induced by cobalt doping in CeOFeAs

Abstract

Pure phases of a new oxyarsenide superconductor of the nominal composition CeOFe_0.9Co_0.1As was successfully synthesized by solid state reaction in sealed silica ampoules at 1180 C. It crystallizes in the layered tetragonal ZrCuSiAs type structure (sp gp P4/nmm) 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.