Single crystal growth and physical properties of La, Co doped (Eu,Ca)FeAs2

Abstract

We report the growth of La and Co doped (Eu,Ca)FeAs2 ((Eu0.5Ca0.4La0.1)(Fe0.97Co0.03)As2, La,Co-(Eu,Ca)112) single crystals via high temperature sintering method and their superconducting properties were investigated. Unlike other iron-based superconductors, single crystals of this compound were relatively easy to obtain by sintering at high temperatures from stoichiometric compositions. Using small amounts of precursor (0.5 g) and optimization of the isothermal temperature and temperature gradient profiles, relatively large (up to 2.8 mm2) 112 single crystals were obtained. X-ray diffraction measurements on the 112 single crystals indicated only (0 0 l) Bragg peaks. Energy dispersive X-ray spectroscopy analysis indicated the composition of the grown 112 single crystals to be (Eu0.54, Ca0.38, La0.09)(Fe0.96, Co0.037)As2. The coexistence of superconductivity and Eu2+ magnetism, as reported in EuFeAs2, was confirmed. The onset of superconducting transition temperature of 30 K (magnetic susceptibility) and 31.8 K (electrical resistivity) was observed in the La,Co-(Eu,Ca)112 single crystal grown by thermal gradient method. Our present results indicating further optimization of Co doping may enhance the superconductivity in these compounds. The La,Co-(Eu,Ca)112 iron-based superconductor, which have unique physical properties and are relatively easy to grow as single crystals, may bring an interesting playground in the field of superconducting materials.