Electronic states of CeT2X20 (T:transition metal, X=Zn and Cd)

Yusuke Hirose,Masaichiro Mizumaki,Ruta Kulkarni,Ryohei Simokasa,Hiroshi Doto,Naomi Kawamura,Yoshitaka Suzuki,Rikio Settai,Fuminori Honda,Arumugam Thamizhavel,Kojiro Mimura

doi:10.1063/1.5043138

Abstract

The electronic state of single crystals of CeIr2(Zn1−xCdx)20 and CePt2Cd20 has been studied by measuring the electrical resistivity ρ and specific heat C. We found that by substituting Zn with Cd, the lattice parameter expands, and the electronic specific heat coefficient γ and A coefficient, which is T2-term in ρ, are enhanced. Our experimental results reveal that the electronic state of the intermediate valence compound CeIr2Zn20 changes to a moderately heavy fermion state due to the negative chemical pressure. On the other hand, C and ρ of CePt2Cd20 show a clear jump and an abrupt change of slope below 0.3 K, respectively, due to a magnetic transition. The relation between the hybridization strength and Ce valence state has also been investigated by X-ray absorption experiment.

Highlights

CeT2X20 (T: transition metals, X=Al, Zn, Cd) crystallizes in the cubic CeCr2Al20 type crystal structure
The ground state of 4f electron in Ce atom strongly depends on X atom
The hybridization strength between the 4f electron and conduction electrons gets weaker in the order of X=Al, Zn, and Cd, where the lattice parameters for X=Al, Zn, and Cd are approximately 14.7, 14.3, and 15.6 Å

Summary

INTRODUCTION

CeT2X20 (T: transition metals, X=Al, Zn, Cd) crystallizes in the cubic CeCr2Al20 type crystal structure. In these systems, the ground state of 4f electron in Ce atom strongly depends on X atom. CeT2Al20 show the paramagnetic ground state with a temperature independent and small magnetic susceptibility,[1] while CeIr2Zn20 and CeRu2Zn20 exhibit an intermediate valence state and heavy fermion state, respectively.[2,3,4] The localized character of the 4f electrons has been observed in CeT2Cd20, showing a Curie-Weiss type magnetic susceptibility at low temperatures.[5,6] The hybridization strength between the 4f electron and conduction electrons gets weaker in the order of X=Al, Zn, and Cd, where the lattice parameters for X=Al, Zn, and Cd are approximately 14.7, 14.3, and 15.6 Å. In order to study the relation between Ce valence and hybridization strength in CeT2X20, we have performed high-resolution X-ray absorption experiment using partial fluorescence yield (PFY) at Ce L3-edge

EXPERIMENTAL

EXPERIMENTAL RESULTS AND DISCUSSIONS

X-ray absorption experiment

SUMMARY