Moewes, AlexanderGreen, Robert J2023-06-2820232023-062023-06-28June 2023https://hdl.handle.net/10388/14751We investigate the electronic properties of materials containing 3d transition metal elements. Such materials are widely available and already in use for industry and technology applications. Their versatility is remarkable and allows for applications in different sectors: copper is a great conductor and is used for electric and thermal transport; cobalt and zinc may be used for energy storage; chromium and nickel act as corrosion protection; titanium is a durable and lightweight construction material; and iron is often exploited as catalyst material for various reactions. Manganese is a promising candidate for magnetic technologies, catalysis, and alkaline battery applications. Hence, the quest for new and advanced technology applications drives the exploration of this class of transition metal materials to uncover scientific and industrial potential. The goal is to develop and tailor materials with unique properties such as high-temperature superconductivity, temperature dependent metal-insulator transitions, colossal magnetoresistance, charge and orbital ordering, among others. Harvesting these properties for technology applications and devices could have a significant impact on the areas of energy transport, energy storage, and high-performance computing. The characterization of materials provides an avenue to explore and understand the origin and mechanisms of these highly sought-after properties. Our analysis aims to (1) establish how the interaction of transition metal atoms with their neighbouring atoms control the electronic and magnetic properties in a material; (2) extract the quantitative hybridization function of transition metal oxides from experiment; and (3) investigate the electronic structure of new materials with mixed-valence and unusual oxidation states. We utilize experimental and theoretical approaches to obtain insights into the electronic structure of the materials under study. Soft x-ray spectroscopy techniques at synchrotron facilities complemented by computational analysis in form of multiplet calculations to model the experimental spectra allow to characterize materials and interpret the results. The determined fundamental properties of 3d transition elements can then be used to tailor material properties during the synthesis process as desired. The interaction of transition metal atoms with their surrounding ligands is extensively investigated throughout all works presented in this thesis. Specifically, the electronic structure of manganese oxides in various oxidation states is investigated with different x-ray spectroscopy techniques and together with multiplet calculations such analysis allows to establish the local electronic environment and hybridization. The extraction of quantitative hybridization functions is demonstrated on the example of archetypical nickel oxide. The improvement of existing quantum impurity models allows crucial insight into the hybridization function of correlated materials and provides an avenue to extract it experimentally. Lastly, we tackle the investigation of the electronic structure of compounds with mixed-valence and unusual oxidation states. Novel phases of manganese oxides synthesized under high-pressure and high-temperature treatment exhibit mixed-valence character for which we determine the concentration of the constituents and analyse charge transfer processes. The analysis of the widely believed unoccupied Mo 4d state of MoO3 in its ground state configuration provides an avenue to shed light on the unusual molybdenum valence and oxidation state. Furthermore, software to easily analyse synchrotron data on the fly has been developed as part of this thesis. The developed program shines when reduction of higher-dimensional multi channel analyzer data is required. This effort combined with high-quality excitation-emission maps allows to distinguish between photon yield techniques and to compare and contrast the different detection mechanisms available at the experimental facility.application/pdfentransition metal oxidescorrelated materialslocal interactionssoft x-ray spectroscopyx-ray absorption spectroscopyx-ray emission spectroscopyresonant inelastic x-ray scatteringmultiplet ligand field theoryAnderson Impurity modelhybridization functionThesis2023-06-28