X-ray photoemission spectrum, electronic structure, and magnetism of UCu2Si2

Abstract

a b s t r a c tThe room temperature X-ray photoemission spectrum of the ferromagnetic compound UCu 2 Si 2 (T C = 100 K) was measured using an Al K ␣ source. Related theoretical spectra were computed from densities of electronic states obtained in the local density approximation (LDA), the generalized gradient approximation (GGA), and using the GGA + U method. The calculated spectrum is in a good agreement with the experimental one. The spin polarized calculations based on the GGA + U approach as well as GGA/LSDA with orbital polarization (OP) corrections taken into account provide values of the total magnetic moment in reasonable agreement with the experimental values ranging between 1.6 and 2.0 B /U atom.

X-ray photoemission spectrum, electronic structure, and magnetism of UCuxSb2

“…To achieve this agreement, the position of the Cu 3d contribution to the XPS spectrum, obtained by the pure LSDA approach, was effectively shifted by about 0.5 eV due to introducing the above parameter U = 2.5 eV within LDA + U, while the position of the U 5f contribution around E F remained nearly the same (by including different U = 2.0 eV) but only its magnitude was diminished. Such shifts by different U values used in calculations of the Cu 3d peaks positions were also considered earlier in the cases of UCuSb 2 [12] and UCu 2 Si 2 [22]. As expected, the spinpolarized (ferromagnetic) DOSs with summed up spin channels, should a little better (or comparably) describe the XPS spectra measured at RT, i.e.…”

“…The U 4f spectrum shows a spin-orbit splitting of 10.8 eV between the 4f 7/2 and 4f 5/2 main components, each of them consisting of a dominant asymmetric line and three satellites on the higher BE side. This kind of the multi-satellite structure has been observed in the core-level spectra of other uranium compounds studied on single-crystalline samples, being not contaminated by oxygen, namely for UAuSb 2 [11], UCu 2 Si 2 [22] and others. The peaks U 4f 7/2 and U 4f 5/2 of UCu 0.83 Sb 2 are situated at 377.7 eV and 388.5 eV of BE, respectively.…”

“…3(c) of Ref. [22]. However, the intensity of the Cu 3d peak in the latter system is almost 2 times higher than that in the studied here UCu 0.83 Sb 2 , which can be explained by nearly 2 times higher concentration of the Cu atoms per f.u.…”

Kondo Screening Effect and Ferromagnetic Order in UCu2Si2

“…2a in Ref. [13] and the total magnetic moment of 1.9 µ B /U at. was given in Table 2 of the same reference.…”

“…The Fermi surface (FS) of UCu 2 Si 2 in the FM state ordered along the c axis was calculated based on the fully-relativistic band structure results, presented in [13], obtained by the full-potential local-orbital (FPLO) code [14] in the local spin-density approximation with orbital--polarization correction (LSDA+OP) [15]. The corresponding densities of states were displayed in Fig.…”