Investigation of the physical properties of the Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd) heavy fermion compounds

TL;DR

This study synthesizes and characterizes new heavy fermion compounds Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd), revealing diverse magnetic behaviors and strong Kondo interactions, with Ce2PdAl7Ge4 exhibiting non-Fermi liquid properties near a quantum critical point.

Contribution

It provides detailed structural, magnetic, and thermal analysis of Ce2MAl7Ge4 compounds, highlighting their complex magnetic interactions and non-Fermi liquid behavior, which are novel insights into heavy fermion systems.

Findings

Ce2CoAl7Ge4, Ce2IrAl7Ge4, Ce2NiAl7Ge4 order magnetically below 1.8, 1.6, and 0.8 K.

Ce2PdAl7Ge4 shows no magnetic order down to 0.4 K.

Ce2PdAl7Ge4 exhibits non-Fermi liquid behavior, indicating proximity to a quantum critical point.

Abstract

We report the synthesis, crystal structure and characterization by means of single crystal x-ray diffraction, neutron powder diffraction, magnetic, thermal and transport measurements of the new heavy fermion compounds Ce$_{2}$MAl$_{7}$Ge$_{4}$ (M = Co, Ir, Ni, Pd). These compounds crystallize in a noncentrosymmetic tetragonal space group P\={4}2$_{1}$m, consisting of layers of square nets of Ce atoms separated by Ge-Al and M-Al-Ge blocks. Ce$_{2}$CoAl$_{7}$Ge$_{4}$, Ce$_{2}$IrAl$_{7}$Ge$_{4}$ and Ce$_{2}$NiAl$_{7}$Ge$_{4}$ order magnetically behavior below $T_{M}=$ 1.8, 1.6, and 0.8 K, respectively. There is no evidence of magnetic ordering in Ce$_{2}$PdAl$_{7}$Ge$_{4}$ down to 0.4 K. The small amount of entropy released in the magnetic state of Ce$_{2}$MAl$_{7}$Ge$_{4}$ (M = Co, Ir, Ni) and the reduced specific heat jump at $T_M$ suggest a strong Kondo interaction in these materials. Ce$_{2}$PdAl$_{7}$Ge$_{4}$ shows non-Fermi liquid behavior, possibly due to the presence of a nearby quantum critical point.