Resonant x-ray diffraction study of the strongly spin-orbit-coupled Mott insulator CaIrO₃

Kenya Ohgushi, Jun-ichi Yamaura, Hiroyuki Ohsumi, Kunihisa Sugimoto, Soshi Takeshita, Akihisa Tokuda, Hidenori Takagi, Masaki Takata, and Taka-hisa Arima

Accepted Tuesday Apr 30, 2013

We performed resonant x-ray diffraction experiments at the L absorption edges for the post-perovskite-type compound CaIrO3 with (t2g)5 electronic configuration. By observing the magnetic signals, we could clearly see that the magnetic structure was a striped order with an antiferromagnetic moment along the c-axis and that the wavefunction of a t2g hole is strongly spin-orbit entangled, the Jeff = 1/2 state. The observed spin arrangement is consistent with theoretical work predicting a unique superexchange interaction in the Jeff = 1/2 state and points to the universal importance of the spin-orbit coupling in Ir oxides, independent of the octahedral connectivity and lattice topology. We also propose that the non-magnetic resonant scattering is a powerful tool for unraveling an orbital state even in a metallic iridate.