Intermediate-valence behavior of the transition-metal oxide CaCu${}_3$Ru${}_4$O${}_{12}$

Abstract

The transition--metal oxide CaCu${}_3$Ru${}_4$O${}_{12}$ with perovskite--type structure shows characteristic properties of an intermediate--valence system. The temperature--dependent susceptibility exhibits a broad maximum around $150-160$ K. At this temperature, neutron powder diffraction reveals a small but significant volume change whereby the crystal structure is preserved. Moreover, the temperature--dependent resistivity changes its slope. NMR Knight shift measurements of Ru reveal a cross--over from high temperature paramagnetic behavior of localized moments to itinerant band states at low temperatures. Additional density--functional theory calculations can relate the structural anomaly with the $d$--electron number. The different experimental and calculational methods result in a mutually consistent description of CaCu${}_3$Ru${}_4$O${}_{12}$ as an intermediate--valent system in the classical sense of having low--energy charge fluctuations.

arXiv comment4 pages, 3 figures

References in corpus (6)

• Non-intrinsic origin of the Colossal Dielectric Constants in CaCu3Ti4O12
• A novel heavy-fermion state in CaCu_3Ru_4O12
• Magneto-electronic Properties of a Ferrimagnetic Semiconductor: The Hybrid Cupromanganite CaCu3Mn4O12
• Heavy-Mass Behavior of Ordered Perovskites ACu3Ru4O12 (A = Na, Ca, La)
• Valence-electron transfer and a metal-insulator transition in a strongly correlated perovskite oxide
• Octahedral Tilting in ACu3Ru4O12 (A=Na,Ca,Sr,La,Nd)

Cited by in corpus (6)

• On the magnetism of Ln{2/3}Cu{3}Ti{4}O{12} (Ln = lanthanide)
• Correlation effects in CaCu3Ru4O12
• CaCu${}_3$Ru${}_4$O${}_{12}$: a high Kondo-temperature transition metal oxide
• Magnetism and unusual Cu valency in quadruple perovskites
• Evidence for a Ru${}^{4+}$ Kondo Lattice in LaCu${}_3$Ru${}_4$O${}_{12}$
• High-field magnetization and magnetoresistance of the $A$-site ordered perovskite oxide CaCu${}_3$Ti${}_{4-x}$Ru${}_x$O${}_{12}$~($0\le x\le 4$)