Suppression of long-range ferromagnetic order in the CexLa1−xTiGe3 system

Abstract

We report specific heat, magnetization, and resistivity measurements on single crystals of ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{TiGe}}_{3}$ systems. When the Ce concentration $x$ is increased, the system changes from a single-ion Kondo system for $x=0.05$ into a ferromagnetic Kondo lattice for $x=1$, where the magnetic part of electrical resistivity reveals a single-ion scaling with $x$. The isoelectric substitution of Ce by La atoms causes a change of the relative strength of competing energy scales of Kondo and RKKY interaction and crystalline electric field (CEF). The substitutions induce the continuous evolution of the Kondo temperature ${T}_{K}$ and the linear variation of ferromagnetic ordering temperature ${T}_{c}$, which are accompanied by a change of the CEF level scheme of the Ce ions. The composition-temperature ($x\text{\ensuremath{-}}T$) phase diagram for ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{TiGe}}_{3}$ is constructed by a combination of magnetization, specific heat, and resistivity measurements. The ferromagnetic ordering temperature is linearly suppressed as $x$ decreases and vanishes near the critical concentration ${x}_{c}=0.1$, but conventional quantum criticality is absent near ${x}_{c}$. The specific heat measurement for $x=0.05$ reveals the power law increase of the electronic specific heat coefficient ${C}_{m}/T\ensuremath{\propto}1/T$ with a large value of $\ensuremath{\sim}3.5$ J/mol ${\mathrm{K}}^{2}$ at $T=0.4\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The magnetic susceptibility for $x=0.05$ also shows a power law dependence $\ensuremath{\chi}(T)\ensuremath{\propto}1/T$ below 10 K.