Optimization of superconductivity in SmFe1-xCoxAsO (x = 0.0, to 1.0)

We report synthesis, structural details and magnetization of SmFe1-xCoxAsO with x ranging from 0.0 to 1.0. It is found that Co substitutes fully at Fe site in SmFeAsO in an iso-structural lattice with slightly compressed cell. The parent compound exhibited known spin density wave (SDW) character below say 150K. Successive doping of Co at Fe site suppressed the SDW transition for x = 0.05 and later induced superconductivity for x = 0.10. 0.15 and 0.20 respectively at 11, 14 and 9K. Clearly the Co substitution at Fe site in SmFe1-xCoxAsO diminishes the Fe SDW character (x = 0.05), introduces bulk superconductivity for x from 0.10 to 0.20 and finally becomes a non-superconducting FM for x above 0.30. The reported AFM ordering of Sm spins is seen from heat capacity Cp(T) at 4.5 K and the same remains invariant with Co doping in SmFe1-xCoxAsO. (author)