5f states in U Ga2 probed by x-ray spectroscopies

• Published in: Physical review. B 2021-07, Vol.104 (4), p.1
• Main Authors: Kolomiets, A V, Paukov, M, Valenta, J, Chatterjee, B, Andreev, A V, Kvashnina, K O, Wilhelm, F, Rogalev, A, Drozdenko, D, Minarik, P, Kolorenč, J, Richter, M, Prchal, J, Havela, L
• Format: Article
• Language: English
• Subjects: Curie temperature; Density functional theory; Dichroism; Electronic structure; Energy resolution; Ferromagnetism; Fluorescence; Magnetic moments; Magnetism; Occupancy; Spectrum analysis; Uranium; Uranium compounds; X ray absorption; X-ray spectroscopy
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.104.045119

The 5 f-based ferromagnet U Ga2 with the Curie temperature TC = 125 K was investigated by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) experiments at the U – M4,5 and Ga–K edges. The position of the U – M4 white line, determined in the high-energy resolution fluorescence detection XAS, suggests that U Ga2 is neither a localized 5 f2 nor an itinerant system with 5f occupancy close to n5f = 3. The analysis of the acquired M4,5 XANES and XMCD spectra indicates the 5f occupancy close to 2.5 and a large orbital magnetic moment of the uranium 5f states (3.18 μB ) that is partly compensated by the antiparallel spin moment (1.31 μB). Thus, the total 5 f magnetic moment of 1.87 μB is obtained, which is smaller than the known bulk magnetization of 3.0 μB per formula unit, while the magnetic moments of the Ga atoms are negligible. Several methods based on density-functional theory were applied and the obtained results were compared with XAS spectral features, the Sommerfeld coefficient of the electronic specific heat, and the size of the U moments and 5f occupancies. A clear correlation is revealed between the U – M4 white-line position of three metallic uranium compounds and the calculated uranium ionicity. It is demonstrated that only electronic structure methods taking appropriate care of orbital magnetism and related atomic multiplet effects can successfully describe all considered properties.