56 巻 (2014) 1 号 p. 36-42
We have performed resonant X-ray diffraction experiments at the Ir L absorption edges for a post-perovskite compound CaIrO3 with a Ir4+:（t2g）5 electronic configuration. By observing the magnetic signals, we could clearly see that the magnetic structure was a striped ordering with antiferromagnetic moments along the c axis and that the wave function of a t2g hole is strongly spin-orbit entangled, the Jeff＝1/2 state. The observed spin arrangement is consistent with a theoretical work predicting a unique superexchange interaction called the quantum compass model. Our studies stimulate further studies for developing novel quantum states in iridium oxides.