Flux growth of Yb_6.6Ir₆Sn₁₆ having mixed-valent ytterbium

Abstract

The compound Yb_6.6Ir₆Sn₁₆ was obtained as single crystals in high yield from the reaction of Yb with Ir and Sn run in excess indium. Single-crystal X-ray diffraction analysis shows that Yb_6.6Ir₆Sn₁₆ crystallizes in the tetragonal space group P4₂/nmc with a = b = 9.7105(7) Å and c = 13.7183(11) Å. The crystal structure is composed of a [Ir₆Sn₁₆] polyanionic network with cages in which the Yb atoms are embedded. The Yb sublattice features extensive vacancies on one crystallographic site. Magnetic susceptibility measurements on single crystals indicate Curie–Weiss law behavior <100 K with no magnetic ordering down to 2 K. The magnetic moment within the linear region (<100 K) is 3.21 μ_B/Yb, which is ∼70% of the expected value for a free Yb₃₊ ion suggesting the presence of mixed-valent ytterbium atoms. X-ray absorption near edge spectroscopy confirms that Yb_6.6Ir₆Sn₁₆ exhibits mixed valence. Resistivity and heat capacity measurements for Yb_6.6Ir₆Sn₁₆ indicate non-Fermi liquid metallic behavior.