Strong Valence Fluctuation Effects in Sm$Tr_2$Al$_{20}$($Tr=$Ti, V, Cr)

TL;DR

This study investigates the low-temperature magnetic and transport properties of SmTr2Al20 compounds, revealing strong valence fluctuations, Kondo effects, and antiferromagnetic order, with systematic variations linked to hybridization strength.

Contribution

It provides the first systematic analysis of valence fluctuations and magnetic ordering in SmTr2Al20 compounds with Tr=Ti, V, Cr, highlighting the role of hybridization.

Findings

Strong valence fluctuations evidenced by Kondo effects.

Antiferromagnetic ordering at low temperatures.

Increased hybridization suppresses magnetic order and induces heavy fermion behavior.

Abstract

We present a single crystal study of low temperature magnetism and transport in Sm$Tr_2$Al$_{20}$ ($Tr =$ Ti, V and Cr). Strong valence fluctuation is manifested as Kondo effects including a large Sommerfeld coefficient $\gamma$, a weak temperature dependence of magnetic susceptibility and a $-\ln T$ dependent resistivity. All the systems order antiferromagnetically at $T_{\rm N}=$ 6.4 K (Ti), 2.3 K (V) and 1.8 K (Cr). Systematic change in the susceptibility, specific heat, and resistivity indicates that stronger $c$-$f$ hybridization in SmV$_2$Al$_{20}$ and SmCr$_2$Al$_{20}$ than in SmTi$_2$Al$_{20}$ suppresses $T_{\rm N}$ and induces the valence fluctuations and moreover field insensitive heavy fermion states.