Discovery of a novel 112-type iron-pnictide and La-doping induced superconductivity in Eu1−xLaxFeAs2 (x = 0-0.15)

We report the discovery and characterization of a novel 112-type iron pnictide EuFeAs2, with La-doping induced superconductivity in a series of Eu1−xLaxFeAs2. The polycrystalline samples were synthesized through solid state reaction method only within a very narrow temperature window around 1073 K. Small single crystals were also grown from a flux method with the size about 100 μm. The crystal structure was identified by single crystal X-ray diffraction analysis as a monoclinic structure with space group of P21/m. From resistivity and magnetic susceptibility measurements, we found that the parent compound EuFeAs2 shows distinct anomalies probably due to the Fe2+ related antiferromagnetic/structural phase transition near 110 K and the Eu2+ related antiferromagnetic phase transition near 40 K. La-doping suppressed both phase transitions to lower temperatures and induced superconducting transitions with a Tc ∼ 11 K for Eu0.85La0.15FeAs2.