Electronic Structure and Magnetism of Ir based Oxides

We have investigated in details the electronic structure of several Ir based oxides where in addition to crystal field and Coulomb repulsion, the spin-orbit coupling (SOC) plays an important role. We shall first consider two Ir based oxides with 4+ (d$^{5}$) charge state of Ir, namely the insulating double perovskite Sr$_{2}$CeIrO$_{6}$ and the metallic rutile IrO$_{2}$, and examine the validity of the novel spin-orbital entangled J$_{eff}$=1/2 states for the description of their electronic structure. In particular, explore in details whether the J$_{eff}$=1/2 state survives for the itinerant metallic IrO$_{2}$. Finally we shall also present our electronic structure calculations on 6H perovskite type iridates where different charge state of Ir (5+, 4.5+, and 4+) may be realized. We show in addition to SOC, the strong intra-dimer hopping play a crucial role for the magnetic ground state and the insulating property of these systems. We shall compare our results with available experiments.