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Studies of valence of selected rare earth silicides determined using Si K and Pd/Rh L2,3 XANES and LAPW numerical studies

DOI: 10.1016/j.nimb.2015.07.125 DOI Help

Authors: P. Zajdel (University of Silesia) , A. Kisiel (Jagiellonian University) , A. Szytuła (Jagiellonian University) , J. Goraus (University of Silesia) , A. Balerna (INFN, Lab DAΦNE-Light) , A. Banaś (Singapore Synchrotron Light Source) , P. Starowicz (Jagiellonian University) , J. Konior (Jagiellonian University) , G. Cinque (Diamond Light Source) , A. Grilli (INFN, Lab DAΦNE-Light)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nuclear Instruments And Methods In Physics Research Section B: Beam Interactions With Materials And Atoms , VOL 364 , PAGES 76 - 84

State: Published (Approved)
Published: December 2015

Abstract: We report on the investigation of Si and Pd/Rh chemical environments using X-ray Absorption Near Edge Spectroscopy in two different families of rare earth silicides R2PdSi3 (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh2?xPdxSi2 (x = 0, 0.5, 0.75, 1.0, 1.5, 1.8, 2.0). The Si K, Pd L3 and Rh L3 absorption edges were recorded in order to follow their changes upon the variation of 4f and 4d5s electron numbers. In both cases it was found that the Si K edge was shifted ?0.5 eV toward lower energies, relative to pure silicon. In the first family, the shift decreases with increasing number of f-electrons, while the Si K edge remains constant upon rhodium–palladium substitution. In all cases the Pd L3 edge was shifted to higher energies relative to metallic Pd. No visible change in the Pd L3 position was observed either with a varying 4f electron count or upon Pd/Rh substitution. Also, the Rh L3 edge did not change. For two selected members, Ho2PdSi3 and HoPd2Si2, the Wien2K’09 (LDA + U) package was used to calculate the electronic structure and the absorption edges. Si K edges were reproduced well for both compounds, while Pd L3 only exhibited a fair agreement for the second compound. This discrepancy between the Pd L3 theory and experiment for the Ho2PdSi3 sample can be attributed to the specific ordered superstructure used in the numerical calculations. The observed changes indicate that despite possessing a formal inter-metallic character, the chemical bond between the R–Si and R–Pd interactions are different. The variation and the direction of the chemical shift of the Si K edge suggests a weak ionic character of the R–Si bonds, in agreement with the localized character of the 4f electrons. In turn, the changes of the Pd/Rh edge are consistent with a metallic band that is affected by its long range chemical environment.

Journal Keywords: Intermetallics; Electronic Band Structure; NEXAFS;Synchrotron Radiation; Silicides

Subject Areas: Physics

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