Substitution effect of Ir oxide with K$_{2}$NiF$_{4}$ type structure

The ground state of Sr$_{2}$IrO$_{4}$ with the K$_{2}$NiF$_{4}$ --type structure is the Mott insulator generated by the competition between the strong spin-orbit coupling (SOC, $\sim$0.5eV) and weak Coulomb interaction ($U$, $\sim$0.5eV). The crystal structure of Sr$_{2}$IrO$_{4}$ consists of stacked two dimensional (2D) IrO$_{2}$ layers with canted antiferromagnetic order ($T_{\mathrm{N}} =$ 250K) and SrO layer, similar to the high-$T_{\mathrm{c}}$ cuprate La$_{2}$CuO$_{4}$. We have investigated the substitution effect for Sr$_{2}$IrO$_{4}$ to confirm the influence of band filling control of Mott insulating state. We synthesized the hole doping sample of Sr$_{\mathrm{2-x}}$K$_{x}$IrO$_{4}$ and electron doping sample of Sr$_{\mathrm{2-x}}$La$_{x}$IrO$_{4}$. From the magnetic susceptibility data, the absolute magnetic moment of Sr$_{\mathrm{2-x}}$La$_{\mathrm{x}}$IrO$_{4}$ decreases with increasing La concentration x (However, $T_{\mathrm{N}}$ value is almost constant, being independent of $x)$. The electrical resistivity data of Sr$_{\mathrm{2-x}}$M$_{x}$IrO$_{4}$ (M $=$ K, La) systematically decreases with increasing $x$. These facts indicate that we succeeded in effective carrier doping to IrO$_{2}$ layer and suggest that the ground state is gradually changed toward to metallic state.