Ce-site dilution in the ferromagnetic Kondo lattice CeRh$_6$Ge$_4$

TL;DR

This study investigates how substituting non-magnetic La atoms for Ce in CeRh$_6$Ge$_4$ affects its magnetic and electronic properties, revealing suppression of ferromagnetism, emergence of non-Fermi liquid behavior, and a transition from coherent Kondo lattice to impurity regimes.

Contribution

It provides comprehensive experimental data on the effects of Ce-site dilution in a ferromagnetic Kondo lattice, highlighting the evolution of magnetic and electronic states with doping.

Findings

Curie temperature decreases with La doping and vanishes above x=0.25.

Non-Fermi liquid behavior observed over a wide doping range.

Strange metal behavior near critical doping x_c=0.26.

Abstract

The heavy fermion ferromagnet CeRh$_6$Ge$_4$ is the first example of a clean stoichiometric system where the ferromagnetic transition can be continuously suppressed by hydrostatic pressure to a quantum critical point. In order to reveal the outcome when the magnetic lattice of CeRh$_6$Ge$_4$ is diluted with non-magnetic atoms, this study reports comprehensive measurements of the physical properties of both single crystal and polycrystalline samples of La$_x$Ce$_{1-x}$Rh$_6$Ge$_4$. With increasing $x$, the Curie temperature decreases, and no transition is observed for $x$ $>$ 0.25, while the system evolves from exhibiting coherent Kondo lattice behaviors at low $x$, to the Kondo impurity scenario at large $x$. Moreover, non-Fermi liquid behavior (NFL) is observed over a wide doping range, which agrees well with the disordered Kondo model for 0.52 $\leq$ $x$ $\leq$ 0.66, while strange metal behavior is revealed in the vicinity of $x_c$ = 0.26.