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

TL;DR

This study combines X-ray photoelectron spectroscopy and first-principles calculations to analyze the valence state and magnetic properties of YbFe$_4$Al$_8$, revealing mixed valence and a specific antiferromagnetic configuration.

Contribution

It provides a detailed analysis of YbFe$_4$Al$_8$'s valence state and magnetic structure using combined experimental and theoretical methods, highlighting the role of Fe sublattices.

Findings

YbFe$_4$Al$_8$ has a valence of 2.81 with mixed Yb$^{2+}$ and Yb$^{3+}$ states.

The most stable magnetic configuration is AFM-C with antiparallel columns of Fe moments.

Fe sublattices carry significant magnetic moments, while Yb valence is influenced by Coulomb U.

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.