Thorium-doping-induced superconductivity up to 56 K in Gd1-xThxFeAsO

We report a new strategy to induce superconductivity in iron-based oxyarsenide. Instead of F- substitution for O2-, we employed Th4+ doping in GdFeAsO with the consideration of lattice match between Gd2O2 layers and Fe2As2 ones. As a result, superconductivity with T-c(onset) as high as 56 K was realized in a Gd0.8Th0.2FeAsO polycrystalline sample. This T-c value is among the highest ever discovered in the iron-based oxypnictides. Copyright (C) EPLA, 2008