Localized Character of 4f Electrons in CeRh$_x$(x=2,3) and CeNi$_x$(x=2,5)

TL;DR

This study uses bulk-sensitive resonant photoemission to analyze Ce 4f electrons in intermetallic compounds, revealing their localized nature despite their metallic environment, challenging the itinerant electron model.

Contribution

It provides direct experimental evidence that Ce 4f electrons remain localized in certain intermetallic compounds, contrasting with the itinerant electron description.

Findings

Ce 4f electrons show localized character in CeRh$_x$ and CeNi$_x$ compounds.

Kondo resonance tails are well described by the Gunnarsson-Sch"onhammer calculation.

Itinerant 4f band models show significant discrepancies with experimental data.

Abstract

We have measured Ce 4f spectral weights of extremely $\alpha$-like Ce-transition metal intermetallic compounds CeRh$_x$ (x=2,3) and CeNi$_x$ (x=2,5) by using the {\it bulk-sensitive} resonant photoemission technique at the Ce $M_5$($3d_{5/2}\to4f$)-edge. Unprecedentedly high energy resolution and longer escape depth of photoemitted electron at this photon energy enabled us to distinguish the sharp Kondo resonance tails at the Fermi level, which can be well described by the Gunnarsson-Sch\"onhammer(GS) calculation based on the Anderson Impurity Hamiltonian. On the other hand, the itinerant 4f band description shows big discrepancies, which implies that Ce 4f electrons retain localized characters even in extremely $\alpha$-like compounds.