Superconductivity at 35 K by self doping in RbGd2Fe4As4O2.

ABSTRACT

We report synthesis, crystal structure and physical properties of a novel quinary compound RbGd2Fe4As4O2. The new iron oxyarsenide is isostructural to the fluo-arsenide KCa2Fe4As4F2, both of which contain separate double Fe2As2 layers that are self hole-doped in the stoichiometric composition. Bulk superconductivity at [Formula see text] K is demonstrated by the measurements of electrical resistivity, dc magnetic susceptibility and heat capacity. An exceptionally high value of the initial slope of the upper critical field ([Formula see text]d[Formula see text]/d[Formula see text] [Formula see text] T K-1) is measured for the polycrystalline sample.