Institute Methods and Instrumentation for Synchrotron Radiation Research
Materials Functionality with meV Resonant Inelastic X-ray Scattering meVRIXS
The simultaneous detection of electronic structure properties and low energy excitation in functional materials is the reason why resonant inelastic X-ray scattering (RIXS) techniques have developed into powerful tools. With meVRIXS we created a meV high resolution instrumentation utilizing the to date underexplored very soft XUV energy range that is unique worldwide. meVRIXS thus allows for highest spectral resolution at the Brillouin zone center of solids. In particular rare earth materials and transition metals are accessible, as are low Z elements. As a complement the mobile solidflexRIXS experiment accesses the deeper soft X-ray core level information.
Figure 1: The surprisingly covalent character of 4f electrons in functional materials such as the transition metal perovskite oxides and Ruddlesden-Popper La2CuO4 as the parent compound of high Tc superconductors has been proven with meV RIXS in the underexplored XUV region. (a) Structure of transition metal perovskite oxides. (b) Schematic of XUV RIXS transitions at Lanthanum. (c) High resolution meV RIXS spectra.
Figure 2: Manifestations of covalency and related trends: (a) Correlation between Lanthanum RIXS 3D1 energy and transition metal ionic radii as a function of nominal 3d electron counts across the periodic table (b) Negative correlation between RIXS 3D1 energy and TM (and Al3+) ionic radii in perovskite oxides and Ruddlesden-Popper La2CuO4 High-spin ionic radii are selected for panel (b).
References:
Liu, C.-Y. et al. Orbital-overlap-driven hybridization in 3d-transition metal perovskite oxides LaMO3 (M = Ti-Ni) and La2CuO4. Commun. Phys. 7, 156 (2024). https://doi.org/10.1038/s42005-024-01642-5
Liu, C.-Y. et al. Role of La 5p in Bulk and Quantum-Confined Solids Probed by the La 5p54f1 3D1 Excitonic Final State of Resonant Inelastic X ray Scattering. J. Phys. Chem. C 127, 11111–11118 (2023). https://doi.org/10.1021/acs.jpcc.3c02011