Orbital state and metal-insulator transition in Ca2-xSrxRuO4 (x=0.0 and 0.09) studied by x-ray absorption spectroscopy -: art. no. 132410

The nature of metal-insulator (MI) transition in a t(2g)-electron system Ca2-xSrxRuO4 has been investigated using O 1s x-ray absorption spectroscopy (XAS). The O 1s XAS data strongly depend on temperature and demonstrate that the hysteresis of the MI transition is accompanied by the hysteresis of the orbital change. An unrestricted Hartree-Fock analysis indicates that the amount of yz/zx hole is discontinuously reduced at the MI transition. In the insulating phase, the amount of 4d yz/zx hole gradually decreases on heating, suggesting that partial orbital fluctuation increases with temperature.