Quantitative study of the f occupation in CeMIn5 and other cerium compounds with hard x-rays

TL;DR

This study uses advanced x-ray spectroscopy techniques to analyze the f-occupation and hybridization in CeMIn5 compounds, revealing a near-integer f-occupation and systematic variations in hybridization strength among heavy fermion materials.

Contribution

It provides a quantitative analysis of f-occupation in CeMIn5 compounds using combined HAXPES and PFY-XAS, with a novel correction method for plasmons and comparison across heavy fermion systems.

Findings

CeMIn5 compounds have an f-occupation close to one.

Hybridization strength decreases from CePd3 to CeRh3B2 to CeRu2Si2.

All three CeMIn5 compounds show identical f-occupation.

Abstract

We present bulk-sensitive hard x-ray photoelectron spectroscopy (HAXPES) data of the Ce3d core levels and lifetime-reduced L edge x-ray absorption spectroscopy (XAS) in the partial fluorescence yield (PFY) mode of the CeMIn5 family with M = Co, Rh, and Ir. The HAXPES data are analyzed quantitatively with a combination of full multiplet and configuration interaction model which allows correcting for the strong plasmons in the CeMIn5 HAXPES data, and reliable weights wn of the different fn contributions in the ground state are determined. The CeMIn5 results are compared to HAXPES data of other heavy fermion compounds and a systematic decrease of the hybridization strength Veff from CePd3 to CeRh3B2 to CeRu2Si2 is observed, while it is smallest for the three CeMIn5 compounds. The f-occupation, however, increases in the same sequence and is close to one for the CeMIn5 family. The PFY-XAS data confirm an identical f-occupation in the three CeMIn5 compounds and a phenomenological fit to these PFY-XAS data combined with a configuration interaction model yields consistent results.