Direct determination of the crystal field parameters of Dy, Er and Yb impurities in the skutterudite compound CeFe$_{4}$P$_{12}$ by Electron Spin Resonance

TL;DR

This paper demonstrates that Electron Spin Resonance can precisely determine the crystal field parameters of Dy, Er, and Yb impurities in CeFe4P12 skutterudites, clarifying their electric ground states.

Contribution

It introduces a method to extract full crystal field parameters for rare-earth impurities in skutterudites using ESR measurements, resolving existing controversies.

Findings

Determined CFPs B4c, B6c, B6t for Dy, Er, Yb in CeFe4P12

ESR-derived CFPs match magnetization data predictions

Clarified the electric crystalline ground state of skutterudites

Abstract

Despite extensive research on the skutterudites for the last decade, their electric crystalline field ground state is still a matter of controversy. We show that Electron Spin Resonance (ESR) measurements can determine the full set of crystal field parameters (CFPs) for the Th cubic symmetry (Im3) of the Ce$_{1-x}$R$_{x}$Fe$_{4}$P$_{12}$ (R = Dy, Er, Yb, $x\lesssim 0.003$) skutterudite compounds. From the analysis of the ESR data the three CFPs, B4c, B6c and B6t were determined for each of these rare-earths at the Ce$^{3+}$ site. The field and temperature dependence of the measured magnetization for the doped crystals are in excellent agreement with the one predicted by the CFPs Bnm derived from ESR.