Evidence for a Ru${}^{4+}$ Kondo Lattice in LaCu${}_3$Ru${}_4$O${}_{12}$

Abstract

Rare $d$-electron derived heavy-fermion properties of the solid-solution series LaCu${}_3$Ru${}_x$Ti${}_{4-x}$O${}_{12}$ were studied for $1\le x\le 4$ by resistivity, susceptibility, specific-heat measurements, and magnetic-resonance techniques. The pure ruthenate ($x=4$) is a heavy-fermion metal characterized by a resistivity proportional to $T^2$ at low temperatures $T$. The coherent Kondo lattice formed by the localized Ru 4$d$ electrons is screened by the conduction electrons leading to strongly enhanced effective electron masses. By increasing titanium substitution the Kondo lattice becomes diluted resulting in single-ion Kondo properties like in the paradigm $4f$-based heavy-fermion compound Ce${}_x$La${}_{1-x}$Cu${}_{2.05}$Si${}_2$ [M. Ocko {\em et al.}, Phys. Rev. B \textbf{64}, 195106 (2001)]. In LaCu${}_3$Ru${}_x$Ti${}_{4-x}$O${}_{12}$ the heavy-fermion behavior finally breaks down on crossing the metal-to-insulator transition close to $x=2$.

9 pages, 8 figures

References in corpus (3)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Heavy-Mass Behavior of Ordered Perovskites ACu3Ru4O12 (A = Na, Ca, La)
• Intermediate-valence behavior of the transition-metal oxide CaCu${}_3$Ru${}_4$O${}_{12}$