Crystalline Electric Field and Kondo Effect in SmOs4Sb12

TL;DR

This study reveals the crystalline-electric-field ground state and Kondo effect in SmOs4Sb12, highlighting the role of multipolar degrees of freedom and the suppression of Kondo screening under high magnetic fields.

Contribution

First identification of the $ ext{Γ}_{67}$ quartet ground state and evidence of Kondo-like screening in SmOs4Sb12 through ultrasound measurements.

Findings

$ ext{Γ}_{67}$ quartet ground state confirmed

Kondo-like screening observed at low fields

Suppression of Kondo effect above 20 T

Abstract

Our ultrasound results obtained in pulsed magnetic fields show that the filled-skutterudite compound SmOs$_4$Sb$_{12}$ has the $\Gamma_{67}$ quartet crystalline-electric-field ground state. This fact suggests that the multipolar degrees of freedom of the $\Gamma_{67}$ quartet play an important role in the unusual physical properties of this material. On the other hand, the elastic response below $\approx$ 20 T cannot be explained using the localized 4$f$-electron model, which does not take into account the Kondo effect or ferromagnetic ordering. The analysis result suggests the presence of a Kondo-like screened state at low magnetic fields and its suppression at high magnetic fields above 20 T even at low temperatures.