CeIr$_{3}$Ge$_{7}$: a local moment antiferromagnetic metal with extremely low ordering temperature

TL;DR

CeIr₃Ge₇ is a unique antiferromagnetic metal with an extremely low ordering temperature of 0.63 K, primarily due to large Ce-Ce bond lengths, and shows no signs of Kondo effects or magnetic frustration.

Contribution

This study reports the discovery of CeIr₃Ge₇ as a low-temperature antiferromagnetic metal with weak RKKY interactions caused by large Ce-Ce distances, expanding understanding of magnetic ordering in Ce-based intermetallics.

Findings

Ordering temperature T_N = 0.63 K

No signatures of Kondo correlations or frustration

Weak RKKY exchange due to large Ce-Ce bond length

Abstract

CeIr$_3$Ge$_7$ is an antiferromagnetic metal with a remarkably low ordering temperature $T_{\rm N}$ = 0.63 K, while most Ce-based magnets order between 2 and 15 K. Thermodynamic and transport properties as a function of magnetic field or pressure do not show signatures of Kondo correlations, interaction competition, or frustration, as had been observed in a few antiferromagnets with comparably low or lower $T_{\rm N}$. The averaged Weiss temperature measured below 10 K is comparable to $T_{\rm N}$ suggesting that the RKKY exchange coupling is very weak in this material. The unusually low $T_{\rm N}$ in CeIr$_3$Ge$_7$ can therefore be attributed to the large Ce-Ce bond length of about 5.7 {\AA}, which is about 1.5 {\AA} larger than in the most Ce-based intermetallic systems.