Crystal field splitting in Srn+1IrnO3n+1 (n = 1,2) iridates probed by x-ray Raman spectroscopy

Nonresonant 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 Srn+1IrnO3n+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 Sr2IrO4 and Sr3Ir2O7, respectively.