Low Temperature Physics: 43, 56 (2017); https://doi.org/10.1063/1.4974186
Физика Низких Температур: Том 43, Выпуск 1 (Январь 2017), c. 68-80
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Electronic and magnetic properties of the ferromagnetic superconductor UCoGeV.N. Antonov Institute for Metal Physics, 36 Vernadsky Str., 03142 Kiev, Ukraine Received June 7, 2016 Аннотация The electronic structure and x-ray magnetic circular dichroism (XMCD) spectra of the ferromagnetic superconductor UCoGe at the U N4,5, Ge and Co K and Co L2,3 edges were investigated theoretically from first principles, using the fully relativistic Dirac linear muffin-tin orbital band structure method. The electronic structure is obtained with the local spin-density approximation (LSDA), as well as with a generalization of the LSDA+U method which takes into account the non-diagonal occupation matrix (in spin indexes) of localized electrons. A stable ferromagnetic ground state was found. The uranium total magnetic moment is quite small (about –0.171μ_{B}) in the LSDA approximation as a result of almost complete cancellation between the spin magnetic moment of 0.657 μ_{B} and the opposite orbital magnetic moment of –0.828 μ_{B}, resulting from strong spin-orbit coupling at the uranium site. Valency of U ion in UCoGe is close to 3+. The ratio orbital and spin magnetic moments M_{l}/M_{s} ranged from 1.163 in the GGA approach up to 2.456 for the LSDA+U calculations is smaller than the corresponding ratio for the free ion U^{3+} value (2.60), it can indicate a significant delocalization of the 5f-electron states due to the hybridization of the U 5f electrons with the conduction band and Co 3d electrons. The line shape of the dichroic spectra at the U M_{5} and M_{4} edges predicted by considering the magneto-optical selection rules as well as the occupation and the energy sequence of the m_{j}-projected partial densities of states. The theoretically calculated XMCD spectra at the U M_{4,5}, Ge and Co K and Co L_{2,3} edges are in good agreement with the experimentally measured spectra. PACS: 71.28.+d Narrow-band systems; intermediate-valence solids; Ключевые слова: heavy fermion, x-ray magnetic circular dichnoism spectra. Published online: November 25, 2016 |