Electronic structure and resonant inelastic x-ray scattering in the mixed 3d-5d transition-metal oxides Sr3CuIrO6, Sr3CuPtO6, and Sr3ZnIrO6

We have investigated the electronic and magnetic properties of one-dimensional Sr3CuIrO6, Sr3ZnIrO6, and Sr3CuPtO6 oxides within the density-functional theory (DFT) using the generalized gradient approximation while taking into account strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. The strong spin-orbit coupling (SOC) in these oxides splits the t2g-type manifold into a lower jeff = 3/2 quartet and an upper jeff = 1/2 doublet. The je f f = 1/2 band is almost completely given by linear combinations of d5/2 states. The occupied je f f = 3/2 band is dominated by d3/2 states with some weight of d5/2 states. We have investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectra at the Ir and Pt L3 edges in Sr3CuIrO6, Sr3ZnIrO6, and Sr3CuPtO6. The experimentally measured RIXS spectrum of Sr3CuIrO6 possesses a sharp feature below 1.3 eV corresponding to transitions within the Ir t2g levels. The excitation located from 3 eV to 5 eV is due to t2g -> eg transitions. The next two high energy structures appear due to d-d transitions between the charge transfer Ir 5dct states and t2g and eg states. The theoretically calculated RIXS spectra of Sr3ZnIrO6 and Sr3CuIrO6 at the Ir L3 edges are very similar due to the similarity of their energy band structures. The RIXS spectrum at the Pt L3 edge of Sr3CuPtO6 significantly differs from the corresponding spectra at the Ir L3 edge of Sr3CuIrO6 and Sr3ZnIrO6. There are not any intra-t2g transitions in Sr3CuPtO6 due to fully occupied t2gstates. Besides, there are additional 5dCu -> eg transitions, where the 5dCu states are derived from the tails of the Cu 3d states inside the Pt atomic spheres.