Synthesis, structure and physical properties of the new Zintl phases Eu11Zn6Sb12 and Eu11Cd6Sb12

Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu{sub 11}Cd{sub 6}Sb{sub 12} and Eu{sub 11}Zn{sub 6}Sb{sub 12}. Both crystallize with the complex Sr{sub 11}Cd{sub 6}Sb{sub 12} structure type-monoclinic, space group C2/m (no. 12), Z=2, with unit cell parameters a=31.979(4) A, b=4.5981(5) A, c=12.3499(14) A, {beta}=109.675(1){sup o} for Eu{sub 11}Zn{sub 6}Sb{sub 12}, and a=32.507(2) A, b=4.7294(3) A, c=12.4158(8) A, {beta}=109.972(1){sup o} for Eu{sub 11}Cd{sub 6}Sb{sub 12}. Their crystal structures are best described as made up of polyanionic {sub {infinity}}{sup 1}[Zn{sub 6}Sb{sub 12}]{sup 22-} and {sub {infinity}}{sup 1}[Cd{sub 6}Sb{sub 12}]{sup 22-} ribbons of corner-shared ZnSb{sub 4} and CdSb{sub 4} tetrahedra and Eu{sup 2+} cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca{sub 3}AlAs{sub 3} and Ca{sub 5}Ga{sub 2}As{sub 6} and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu{sub 11}Cd{sub 6}Sb{sub 12} orders anti-ferromagnetically below 7.5 K, while Eu{sub 11}Zn{sub 6}Sb{sub 12} does not order down to 5 K. Resistivity measurementsmore » confirm that Eu{sub 11}Cd{sub 6}Sb{sub 12} is poorly metallic, as expected for a Zintl phase. - Graphical abstract: The synthesis, structure determination from single-crystal X-ray diffraction and magnetic properties of Eu{sub 11}Zn{sub 6}Sb{sub 12} and Eu{sub 11}Cd{sub 6}Sb{sub 12} are reported. Both compounds crystallize with the monoclinic space group C2/m, and their structure can be viewed as built of ZnSb{sub 4} or CdSb{sub 4} tetrahedra, which are connected through common corners and exo-bonds.« less