Spin-Orbit Coupling in Iridium-Based 5d Compounds Probed by X-ray Absorption Spectroscopy

摘要

We have performed x-ray absorption spectroscopy (XAS) measurements on aseries of Ir-based 5d transition metal compounds, including Ir, IrCl3, IrO2,Na2IrO3, Sr2IrO4, and Y2Ir2O7. By comparing the intensity of the "white-line"features observed at the Ir L2 and L3 absorption edges, it is possible toextract valuable information about the strength of the spin-orbit coupling inthese systems. We observe remarkably large, non-statistical branching ratios inall Ir compounds studied, with little or no dependence on chemical composition,crystal structure, or electronic state. This result confirms the presence ofstrong spin-orbit coupling effects in novel iridates such as Sr2IrO4, Na2IrO3,and Y2Ir2O7, and suggests that even simple Ir-based compounds such as IrO2 andIrCl3 may warrant further study. In contrast, XAS measurements on Re-based 5dcompounds, such as Re, ReO2, ReO3, and Ba2FeReO6, reveal statistical branchingratios and negligible spin-orbit coupling effects.