Electronic structure of YbFe${}_4$Al${}_8$ antiferromagnet: A combined X-ray photoelectron spectroscopy and first-principles study

Abstract

Depending on their chemical composition, Yb compounds often exhibit different valence states. Here we investigate the valence state of YbFe${}_4$Al${}_8$ using X-ray photoelectron spectroscopy (XPS) and first-principles calculaions. The XPS valence band of YbFe${}_4$Al${}_8$ consists of two contributions coming from divalent (Yb${}^{2+}$) and trivalent (Yb${}^{3+}$) configurations. The determined value of the valence at room temperature is 2.81. Divalent and trivalent contributions are also observed for core-level Yb 4$d$ XPS spectra. We study several collinear antiferromagnetic models of YbFe${}_4$Al${}_8$ from the first-principles and for comparison we also consider LuFe${}_4$Al${}_8$ with a fully filled 4$f$ shell. We predict that only Fe sublattices of YbFe${}_4$Al${}_8$ carry significant magnetic moments and that the most stable magnetic configuration is AFM-C with antiparallel columns of magnetic moments. We also present a Mullliken electronic population analysis describing charge transfer both within and between atoms. In addition, we also study the effect of intra-atomic Coulomb U repulsion term applied for 4$f$ orbitals on Yb valence and Fe magnetic moments.

13 pages, 9 figures

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