A Self-Doped Oxygen-Free High-Critical-Temperature (High-T-C) Superconductor: Smffeas

A new iron-base superconductor SmFFeAs is synthesized via solid-state metathesis reaction by using SmFCI and LiFeAs as precursors. The compound crystallized in the tetragonal ZrCuSiAs-type structure with the space group P4/nmm and lattice parameters of a = 3.9399(0) angstrom and c = 8.5034(1) angstrom. The superconducting diamagnetic transition occurs at 56 K for the parent compound, which confirmed by the resistivity and magnetic susceptibility. The appearance of superconductivity without extrinsic doping could be ascribed to the self-doping owing to the mixed valence of Sm ions. The as-synthesized SmFFeAs serves as a new self-doped parent compound for oxygen-free high-critical-temperature (high-T-c) superconductors.