Usachov, D.Y.; Bokai, K.A.; Poelchen, G.; Stolyarov, V.S.; Fedorov, A.V.; Kliemt, K.; Khim, S.; Caroca-Canales, N.; Krellner, C.; Vyalikh, D.V.: Surface effects in x-ray absorption spectra of lanthanides: Focus on strongly correlated cerium materials. Physical Review B 112 (2025), p. 035137/1-9
10.1103/blg4-bxl5
Open Access Version
Abstract:
Lanthanide (Ln) materials are widely studied using x-ray absorption spectroscopy (XAS), primarily at the Ln 3𝑑 edge, with less attention given to the 4𝑑 edge. Spectral features are usually analyzed in relation to bulk properties with surface effects rarely considered. In this study, we explore surface phenomena and their impact on XAS spectra, using as examples the antiferromagnetic (AFM) Kondo lattice CeRh2Si2 , where we thoroughly examine both the 3𝑑 and 4𝑑 edges, and AFM LnRh2Si2 (Ln = Tm, Tb, and Pr), where our focus is primarily on the 3𝑑 edge. We observe significant contributions from surface effects in the 3𝑑 XAS spectra, even when measured in the total electron yield regime. We find evidence of Ce 4𝑓 moment reorientation at the Ce-terminated surface of CeRh2Si2, linked to changes in the crystal electric field at the surface. By modeling the Ce 3𝑑 and 4𝑑 XAS spectra, we not only distinguish between surface and bulk properties but also reveal the fine multiplet structure and the characteristic shape of the giant resonance associated with |𝑀𝐽⟩ states. These findings provide insights into 4𝑓 -derived surface phenomena and their distinction from bulk electronic properties, while also emphasizing the general importance of surface sensitivity in XAS measurements of Ln materials.