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

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 $\le$ $x$ $\le$ 0.66, while strange metal behavior is revealed in the vicinity of $x_c$ = 0.26.

6 pages, 5 figures