Crystal Structure and Physical Properties of New Ternary Gallides Eu₂Rh₃Ga₉ and Eu₂Ir₃Ga₉

Abstract

The compounds Eu 2 Rh 3 Ga 9 and Eu 2 Ir 3 Ga 9 were synthesized by melting the elements in sealed tantalum tubes with subsequent annealing at 600 °C. Both gallides are isotypic with Y 2 Co 3 Ga 9 (space group Cmcm, Pearson symbol oC56, Z = 4) as evidenced by single crystal structure analysis: a = 12.9902(6), b = 7.6141(4), c = 9.7433(5) Å , RF = 0.025, 617 structure factors, 42 variable parameters for Eu 2 Rh 3 Ga 9 , and a = 13.0371(7), b = 7.6017(4), c = 9.6972(6) Å , RF = 0.032, 645 reflections, 42 variables for Eu 2 Ir 3 Ga 9 . Magnetic susceptibility measurements as well as X-ray absorption spectra indicate the 4f 7 electronic configuration of europium (Eu 2+ ) with significant admixture of the 4f 6 state in both compounds.