Pressure Effects on the 4f Electronic Structure of Light Lanthanides

TL;DR

This study investigates how high pressure affects the 4f electronic structure of light lanthanides like Ce, Pr, and Nd using x-ray emission spectra, revealing satellite peak changes linked to volume collapse and hybridization effects.

Contribution

It provides new experimental data and theoretical analysis on 4f electronic behavior under pressure, highlighting the role of satellite structures and hybridization in f-electron phenomena.

Findings

Satellite peak reduction correlates with volume collapse in Ce and Pr.

Hybridization effects can obscure expected satellite changes.

Changes in 4f occupation are more indicative of electronic evolution than moment reduction.

Abstract

Using the satellite structure of the $L_{\gamma1}$ line in non-resonant x-ray emission spectra, we probe the high-pressure evolution of the bare 4f signature of the early light lanthanides at ambient temperature. For Ce and Pr the satellite peak experiences a sudden reduction concurrent with their respective volume collapse (VC) transitions. These new experimental results are supported by calculations using state-of-the-art extended atomic structure codes for Ce and Pr, and also for Nd, which does not exhibit a VC. Our work suggests that changes to the 4f occupation are more consistently associated with evolution of the satellite than is the reduction of the 4f moment. Indeed, we show that in the case of Ce, mixing of a higher atomic angular momentum state, driven by the increased hybridization, acts to obscure the expected satellite reduction. These measurements emphasize the importance of a unified study of a full set of microscopic observables to obtain the most discerning test of the underlying, fundamental f-electron phenomena at high pressures.