Structure, magnetism, and transport properties for Ca doping in Sr2IrO4

An immediate quenching using liquid N2 is applied for synthesizing the 5d transition-metal oxides (Sr1-x Ca x )2IrO4 (0 ≤ x ≤ 0.15) single phase. X-ray diffraction together with Rietveld refinement shows that the lattice parameters along a and c directions and the bond angle of Ir-O2-Ir decrease with the increase of Ca content. X-ray Absorption Fine Spectroscopy measurements prove that the valence of Ir and the average Ir-O bond-length substantially remain unchanged with Ca content increasing in the phase. The effective magnetic moment μ eff and Néel temperature T N decrease simultaneously with increased Ca content. Electrical resistivity shows complex temperature dependence behavior, which follows the three-dimensional variable range hopping behavior at low temperature, Arrhenius-type behavior at middle-temperature, and a weak electronic localization in quasi-two-dimensional at high temperature.