Direct determination of the crystal field parameters of Dy, Er, and Yb impurities in the skutterudite compoundCeFe4P12by electron spin resonance

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 ${T}_{h}$ cubic symmetry $(Im3)$ of the ${\text{Ce}}_{1\ensuremath{-}x}{R}_{x}{\text{Fe}}_{4}{\text{P}}_{12}$ ($R=\text{Dy}$, Er, Yb; $x\ensuremath{\lesssim}0.003$) skutterudite compounds. From the analysis of the ESR data the three CFPs ${B}_{4}^{c}$, ${B}_{6}^{c}$, and ${B}_{6}^{t}$ were determined for each of these rare earths at the ${\text{Ce}}^{3+}$ site. The field and temperature dependence of the measured magnetization for the doped crystals is in excellent agreement with the one predicted by the CFPs ${B}_{n}^{m}$ derived from ESR.