Adding depth resolution to resonant inelastic X-ray scattering by means of standing-wave excitation

Resonant inelastic X-ray scattering (RIXS) is a photon-in/photon-out synchrotron-based spectroscopy that uniquely probes the charge transfer, dd, magnetic, phonon and other excitations in correlated oxides and other systems.RIXS is considered to be a probe of bulk properties, reaching depths of the order of 1000 Å. It is thus desirable to give RIXS more quantitative depth resolution, for example to investigate interfaces in oxide heterostructures, which are known to show emergent properties (e.g. interface-induced ferromagnetism at the La_1.85Sr_0.15CuO₄/La_0.67Sr_0.33MnO₃ (LSCO/LSMO) heterostructures, 2D electron gases at LaAlO₃/SrTiO₃ (LAO/STO) heterostructure) not present in the single constituents. Here, we demonstrate that, by using standing-wave (SW) excitation from multilayer heterostructures, interface-specific RIXS information can be obtained. We present the results of SW-RIXS measurements on LSCO/LSMO and LAO/STO superlattices. SW effects are clearly observed on the RIXS excitations for these systems and were found to have different depth distribution. SW-RIXS will open up a new spatial dimension to this already powerful technique.