Crystal field splitting in Sr$_{n+1}$Ir$_n$O$_{3n+1}$ ($n$ = 1, 2) iridates probed by x-ray Raman spectroscopy

TL;DR

This study uses non-resonant X-ray Raman spectroscopy to investigate the electronic structure and crystal field splitting in Sr$_{n+1}$Ir$_n$O$_{3n+1}$ iridates, providing detailed orbital energy insights.

Contribution

It demonstrates a bulk-sensitive method to measure crystal field splittings in iridates, revealing specific orbital energy differences and tetragonal distortions.

Findings

Measured t2g-eg splitting values for Sr2IrO4 and Sr3Ir2O7.

Identified orbital transitions involving Ir 5d orbitals.

Provided quantitative insights into crystal field effects in iridates.

Abstract

Non-resonant Raman spectroscopy in the hard X-ray regime has been used to explore the electronic structure of the first two members of the Ruddlesden-Popper series Sr$_{n+1}$Ir$_n$O$_{3n+1}$ of iridates. By tuning the photon energy transfer around 530 eV we have been able to explore the oxygen K near edge structure with bulk sensitivity. The angular dependence of the spectra has been exploited to assign features in the 528-535 eV energy range to specific transitions involving the Ir 5d orbitals. This has allowed us to extract reliable values for both the t2g-eg splitting arising from the cubic component of the crystal field (10Dq), in addition to the splitting of the eg orbitals due to tetragonal distortions. The values we obtain are (3.8, 1.6) eV and (3.55, 1.9) eV for Sr$_2$IrO$_4$ and Sr$_3$Ir$_2$O$_7$, respectively.