Intermediate valence to heavy fermion through a quantum phase transition in Yb3(Rh1−xTx)4Ge13 (T=Co,Ir) single crystals

Single crystals of ${\mathrm{Yb}}_{3}(\mathrm{Rh}{}_{1\ensuremath{-}x}{T}_{x}){}_{4}{\mathrm{Ge}}_{13}$ $(T\phantom{\rule{0.5em}{0ex}}=\phantom{\rule{0.5em}{0ex}}\mathrm{Co},\phantom{\rule{0.16em}{0ex}}\mathrm{Ir})$ have been grown using the self-flux method. Powder x-ray diffraction data on these compounds are consistent with the cubic structure with space group $Pm\overline{3}n$. Intermediate-valence behavior is observed in ${\mathrm{Yb}}_{3}(\mathrm{Rh}{}_{1\ensuremath{-}x}{T}_{x}){}_{4}{\mathrm{Ge}}_{13}$ upon $T$ = Co doping, while $T$ = Ir doping drives the system into a heavy-fermion state. Antiferromagnetic order is observed in the Ir-doped samples ${\mathrm{Yb}}_{3}(\mathrm{Rh}{}_{1\ensuremath{-}x}{T}_{x}){}_{4}{\mathrm{Ge}}_{13}$ for $0.5lx\ensuremath{\le}1$ with ${T}_{N}=0.96$ K for ${\mathrm{Yb}}_{3}\mathrm{Ir}{}_{4}{\mathrm{Ge}}_{13}$. With decreasing $x$, the magnetic order is suppressed towards a quantum critical point around ${x}_{c}$ = 0.5, accompanied by non-Fermi-liquid behavior evidenced by logarithmic divergence of the specific heat and linear temperature dependence of the resistivity. The Fermi-liquid behavior is recovered with the application of large magnetic fields.