$EuTM_{2}Ga_{8}$ (TM= Co, Rh, Ir) - A Contribution to the Chemistry of the $CeFe_{2}Al_{8}$ -type Compounds

Sichevych, O.; Burkhardt, U.; Kohout, M.; Cardoso-Gil, R.; Schnelle, W.; Schmidt, M.; Grin, Yu.; Borrmann, H.

doi:10.1021/ic900573w

Journal Article

$EuTM_{2}Ga_{8}$ (TM= Co, Rh, Ir) - A Contribution to the Chemistry of the $CeFe_{2}Al_{8}$ -type Compounds

Sichevych, O. ; Kohout, M. ; Schnelle, W. ; Borrmann, H. ; Cardoso-Gil, R. ; Schmidt, M. ; Burkhardt, U. ; Grin, Y. ; DESY

2009
American Chemical Society Washington, DC

Inorganic chemistry 48, 6261 - 6270 (2009) [10.1021/ic900573w]

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Please use a persistent id in citations: doi:10.1021/ic900573w

Abstract: The isostructural compounds EuTM(2)Ga(8) (TM = Co, Rh, Ir) were prepared by direct reaction of the elements by high-frequency thermal treatment. All three phases are isotypic with CeFe(2)Al(8) (space group Pbam, Pearson symbol oP44, Z = 4). The crystal structure was established from single-crystal X-ray diffraction data: a = 12.4322(7) A, b = 14.3814(9) A, and c = 4.0378(2) A for EuCo(2)Ga(8); a = 12.6001(6) A, b = 14.6757(7) A, and c = 4.1172(2) A for EuRh(2)Ga(8); and a = 12.6237(7) A, b = 14.6978(8) A, and c = 4.1486(2) A for EuIr(2)Ga(8), respectively. Analysis of the chemical bonding in EuRh(2)Ga(8) with the electron localizability tools reveals formation of the 3D [Rh(2)Ga(8)] polyanion build by polar covalent bonds. Europium interacts in two ways with the polyanion: mainly as a cation by charge transfer and additionally covalently by means of the electrons of the inner shells. Magnetic susceptibility measurements show Curie-Weiss paramagnetic behavior above 40 K with effective magnetic moments of 7.81, 8.05, and 8.27 micro(B)/f.u. for EuTM(2)Ga(8) (TM = Co, Rh, Ir). Antiferromagnetic ordering of Eu moments is observed in all three compounds below 20 K. Independently on the chemical composition of the coordination sphere, magnetic behavior and, especially, X-ray absorption spectra indicate predominantly the 4f(7) electronic configuration of europium with small admixture of the 4f(6) state.

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