Spin-orbit coupling in iridium-based 5d compounds probed by x-ray absorption spectroscopy

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2012-11, Vol.86 (19)
• Main Authors: Clancy, J P, Chen, N, Kim, C Y, Chen, W F, Plumb, K W, Jeon, B C, Noh, T W, Kim, Young-June
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Condensed matter; Crystal structure; Iridium compounds; Spin-orbit interactions; Transition metal compounds; X-rays
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.86.195131

We have performed x-ray absorption spectroscopy (XAS) measurements on a series of Ir-based 5d transition metal compounds, including Ir, IrCl sub(3), IrO sub(3), Na sub(2) IrO sub(3), Sr sub(2) IrO sub(4), and Y sub(2) Ir sub(2) O sub(7). By comparing the intensity of the "white-line" features observed at the Ir L sub(2) and L sub(3) absorption edges, it is possible to extract valuable information about the strength of the spin-orbit coupling in these systems. We observe remarkably large, nonstatistical 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 Sr sub(2) IrO sub(3), Na sub(2) IrO sub(3), and Y sub(2) Ir sub(2) O sub(7), and suggests that even simple Ir-based compounds such as IrO sub(2) and IrCl sub(3) may warrant further study. In contrast, XAS measurements on Re-based 5d compounds, such as Re, ReO sub(2), ReO sub(3), and Ba sub(2) FeReO sub(6), reveal statistical branching ratios indicative of negligible spin-orbit coupling effects.