Enhanced electrical conductivity and diluted Ir4+ spin orders in electron doped iridates Sr2-xGaxIrO4.

Sr2IrO4 represents a fascinating system to study comparable electronic correlations and spin-orbit couplings, and recently attracts considerable attention in high-temperature superconductivity. Here, we report on the transport and magnetic properties in gallium-doped Sr2IrO4. A metallic state is discovered when doping x is over 0.1, which could be understood in terms of the quickly decreased energy gap and increased carrier concentration. In addition to the high-temperature magnetic transition (TC>200 K), a low-temperature one (T'C ) is also observed for the x=0.05-0.10 samples. Both of the magnetic states are found to be canted antiferromagnetism. The low-temperature phase is strongly depressed by doping and vanishes when doping is further increased, which is probably stabilized by the long-way exchange interactions of diluted Ir4+ spins via Ir3+ ions. Our studies provide an insight into the electrical and magnetic states tuned by chemical doping in Sr2IrO4, thereby facilitating the seeking of superconductivity in this system. [ABSTRACT FROM AUTHOR]