R ₃Au _6+xAl ₂₆T (R = Ca, Sr, Eu, Yb; T = Early transition metal): A large family of compounds with a stuffed BaHg ₁₁ structure type grown from aluminum flux

A collection of new quaternary intermetallic compounds with a cubic, stuffed BaHg ¹¹ structure type has been synthesized by the combination of a divalent rare earth or alkaline earth metal R, an early transition metal T, and gold in an excess of molten aluminum. Structural characterization of these R ₃Au _6+xAI ₂₆T compounds by powder and single crystal X-ray diffraction indicates that the unit cell varies with the radii of the early transition metal T and the rare earth/alkaline earth R as expected. The element T (where T = group 4, 5, 6, and 7 element) appears to be responsible for the stabilization of up to 43 different members of the R ₃Au _6+xAI ₂₆T family of compounds. Varying amounts of disorder and trends in partial occupancies of the Au stuffed site - the site that is vacant in the parent compound BaHg ₁₁ - are also indicated by the diffraction studies of this family of compounds. Magnetic susceptibility data reveals that the transition metal atoms in these materials do not possess local magnetic moments. For the magnetic rare earth containing materials, the europium compounds undergo a ferromagnetic transition at 10 K, and the ytterbium analogues show mixed valent behavior. Band structure calculations also support a mixed valent state for Yb in these compounds.