Electronic structure is a common denominator of basic properties of actinide systems. U compounds are at the threshold of localization of the 5f states. This brings excellent opportunities to observe phenomena related to the onset of localization (as anomalous superconductivity) but the degree of localization is difficult to quantify. U hydrides (a- or ß-UH3, UH2) are FM with relatively high TC (exceeding 100 K), and the question is whether they are conventional band magnets, well described by DFT calculations, or the e-e correlations play a more fundamental role. Electron spectroscopies (XPS, UPS, BIS) bring more direct information (taken with some precautions) on electronic states than bulk properties.
We used a combination of thin-film synthesis of U hydrides (provides clean surfaces for high-quality PES studies) with in-situ spectroscopic and ex-situ bulk (XRD, magnetic, transport) studies to reveal reasons for high TC in UH3 [1]. In addition, systems with Mo and Zr substitutions, which give elevated TC values (up to 203 K), or stabilize transient a-UH3 phase in bulk [2], were studied in film form. The confrontation with results of various computations indicates that DMFT-type of calculations are needed to understand the valence-band spectra, reflecting features of atomic multiplets, with intensity and energy of individual lines affected by hybridization.
[1] L. Havela et al., J. Electron Spectrosc. Relat. Phenom. 239 (2020) 146904.
[2] L. Havela et al., J Magn. Magn. Mat. 400 (2016) 130-136.