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

TL;DR

This study uses X-ray absorption spectroscopy to investigate spin-orbit coupling in various Ir-based 5d compounds, revealing strong effects across different structures and compositions, unlike Re-based compounds.

Contribution

It demonstrates that Ir compounds exhibit significant spin-orbit coupling regardless of their chemical or structural differences, confirmed by large branching ratios in XAS measurements.

Findings

Ir compounds show large, non-statistical branching ratios indicating strong spin-orbit coupling.

Re compounds display statistical branching ratios, suggesting negligible spin-orbit effects.

Ir-based compounds like Sr2IrO4 and Na2IrO3 are confirmed to have strong spin-orbit interactions.

Abstract

We have performed x-ray absorption spectroscopy (XAS) measurements on a series 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 to extract valuable information about the strength of the spin-orbit coupling in these systems. We observe remarkably large, non-statistical branching ratios in all Ir compounds studied, with little or no dependence on chemical composition, crystal structure, or electronic state. This result confirms the presence of strong spin-orbit coupling effects in novel iridates such as Sr2IrO4, Na2IrO3, and Y2Ir2O7, and suggests that even simple Ir-based compounds such as IrO2 and IrCl3 may warrant further study. In contrast, XAS measurements on Re-based 5d compounds, such as Re, ReO2, ReO3, and Ba2FeReO6, reveal statistical branching ratios and negligible spin-orbit coupling effects.