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

Highlights

• Bulk-sensitive valence determination in CeMIn₅ via HAXPES and quantitative analysis.

• Comparison to other Ce systems of various hybridization strengths.

• Identical f-occupation in CeMIn₅ compounds confirmed by L-edge PFY-XAS.

• Conclusion: transition elements act as perturbation only.

• Crystal-field wave function may have important impact on ground state formation.

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 $w_n$ 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 V_eff 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.