%0 Journal Article
%A Kazem, Nasrin
%A Hurtado, Antonio
%A Klobes, Benedikt
%A Kauzlarich, Susan M.
%A Hermann, Raphael
%T Eu$_{9}$Cd$_{4–x}$CM$_{2+x–y□y}$Sb$_{9}$: Ca$_{9}$Mn$_{4}$Bi$_{9}$-Type Structure Stuffed with Coinage Metals (Cu, Ag, and Au) and the Challenges with Classical Valence Theory in Describing These Possible Zintl Phases
%J Inorganic chemistry
%V 54
%N 3
%@ 1520-510X
%C Washington, DC
%I American Chemical Society
%M FZJ-2015-02493
%P 850 - 859
%D 2015
%X The synthesis, crystal structure, magnetic properties, and europium Mössbauer spectroscopy of the new members of the 9–4–9 Zintl family of Eu9Cd4–xCM2+x–y□ySb9 (CM = coinage metal: Au, Ag, and Cu) are reported. These compounds crystallize in the Ca9Mn4Bi9 structure type (9–4–9) with the 4g interstitial site almost half-occupied by coinage metals; these are the first members in the 9–4–9 family where the interstitial positions are occupied by a monovalent metal. All previously known compounds with this structure type include divalent interstitials where these interstitials are typically the same as the transition metals in the anionic framework. Single-crystal magnetic susceptibility data indicate paramagnetic behavior for all three compounds with antiferromagnetic ordering below 10 K (at 100 Oe) that shifts to lower temperature (<7 K) by applying a 3 T magnetic field. 151Eu Mössbauer spectra were collected on polycrystalline powder samples of Eu9Cd4–xCM2+x–y□ySb9 at 50 and 6.5 K in order to evaluate the valence of Eu cations. Although the Zintl formalism states that the five crystallographically distinct Eu sites in Eu9Cd4–xCM2+x–y□ySb9 should bear Eu2+, the Mössbauer spectral isomer shifts are clearly indicative of both 2+ and 3+ valence of the Eu cations with the Cu- and Au-containing compounds showing higher amounts of Eu3+. This electronic configuration leads to an excess of negative charge in these compounds that contradicts the expected valence-precise requirement of Zintl phases. The spectra obtained at 6.5 K reveal magnetic ordering for both Eu2+ and Eu3+. The field dependence of Eu2+ indicates two distinct magnetic sublattices, with higher and lower fields, and of a small field for Eu3+. The site symmetry of the five Eu sites is not distinguishable from the Mössbauer data.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000348887400021
%$ pmid:25354329
%R 10.1021/ic502061w
%U https://juser.fz-juelich.de/record/189315