The Gallides SrRh₂Ga₂, SrIr₂Ga₂, and Sr₃Ir₄Ga₄

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) ˚ A, R F = 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) ˚ A, R F = 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 4 f 7 electronic configuration of europium (Eu 2+) with significant ad-mixture of the 4 f 6 state in both compounds.

Yb6Ir5Ga7- A MgZn2Superstructure

“…The Ir–Ga distances range from 260 to 265 pm, slightly longer than the sum of the covalent radii for Ir + Ga of 251 pm . Slightly shorter Ir–Ga distances of 243 pm occur in Sr 3 Ir 4 Ga 4 …”

“…A first single crystal with the refined composition of Yb 6 Ir 5 Ga 7 was separated from a sample with the starting atomic ratio of 3Yb:4Ir:4Ga (using a similar annealing sequence) when searching for isotypic compounds of Sr 3 Ir 4 Ga 4 . Yb 6 Ir 5 Ga 7 was the major product of that sample accompanied by a yet unknown minor impurity phase.…”