In this article,the Sm-doping single crystals Ca1-xSmxFe2As2（x = 0 0.2） were prepared by the Ca As flux method,and followed by a rapid quenching treatment after the high temperature growth.The samples were characterized by structural,resistive,and magnetic measurements.The successful Sm-substitution was revealed by the reduction of the lattice parameter c,due to the smaller ionic radius of Sm3＋than Ca2＋.Superconductivity was observed in all samples with onset Tc varying from 27 K to 44 K upon Sm-doping.The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples.Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x 〉 0.10.The doping dependences of the c-axis length and onset Tc were summarized.The high-Tc observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution.
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 100μm. The crystal structure was identified by single crystal X-ray diffraction analysis as a monoclinic structure with space group of P2 1/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 110K and the Eu2＋ related antiferromagnetic phase transition near 40K. La-doping suppressed both phase transitions to lower temperatures and induced superconducting transitions with a Tc - 11 K for Eu0.85La0.15FeAs2.
Here we report the discovery of superconductivity in the ternary LaRu2As2 compound. The polycrystalline LaRu2As2 samples were synthesized by the conventional solid state reaction method. Powder X-ray diffraction analysis indicates that LaRu2As2 crystallizes in the ThCr2Si2-type crystal structure with the space group 14/ mmm （No. 139）, and the refined lattice parameters are a = 4.182（6）A and c = 10.590（3）A. The temperature dependent resistivity measurement shows a clear superconducting transition with the onset Tc （critical tempera- ture） at 7.8 K, and zero resistivity happens at 6.8 K. The upper critical field at zero temperature μ0Hc2（0） was estimated to be 1.6 T from the resistivity measurement. DC magnetic susceptibility measurement shows a bulk superconducting Meissner transition at 7.0 K, and the isothermal magnetization measurement indicates that LaRu2As2 is a type-II superconductor.
