Electronic structure of $RE$AuMg and $RE$AgMg ($RE$ = Eu, Gd, Yb)

TL;DR

This study investigates the electronic structure of specific Eu, Gd, and Yb intermetallic compounds using x-ray photoelectron spectroscopy and compares results with band structure calculations, revealing insights into valence states and band characteristics.

Contribution

It provides detailed experimental and theoretical analysis of the electronic structure of EuAuMg, GdAuMg, YbAuMg, and GdAgMg intermetallics, highlighting the valence states and narrow d bands.

Findings

Yb and Eu are divalent; Gd is trivalent.

Narrow Au and Ag d bands resemble impurity states.

Good agreement between experiment and calculations with spin-orbit and correlation effects.

Abstract

We have investigated the electronic structure of the equiatomic EuAuMg, GdAuMg, YbAuMg and GdAgMg intermetallics using x-ray photoelectron spectroscopy. The spectra revealed that the Yb and Eu are divalent while the Gd is trivalent. The spectral weight in the vicinity of the Fermi level is dominated by the mix of Mg $s$, Au/Ag $sp$ and $RE$ $spd$ bands, and not by the $RE$ $4f$. We also found that the Au and Ag $d$ bands are extraordinarily narrow, as if the noble metal atoms were impurities submerged in a low density $sp$ metal host. The experimental results were compared with band structure calculations, and we found good agreement provided that the spin-orbit interaction in the Au an Ag $d$ bands is included and correlation effects in an open $4f$ shell are accounted for using the local density approximation + Hubbard $U$ scheme. Nevertheless, limitations of such a mean-field scheme to explain excitation spectra are also evident.