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Abstract:
Polycrystalline samples of Ba3CuOs2O9 and Ba3ZnOs2O9 were synthesized by solid-state reactions. Ba(3)Cu(0)s(2)O(9) crystallizes in Cmcm, while Ba3ZnOs2O9 adopts the hexagonal space group P6(3)/mmc. Both the crystal structures consist of face-sharing Os-centered octahedra forming dimer-like Os2O9 units, which are interconnected by corner-sharing CuO6, or ZnO6 octahedra, respectively. In Ba(3)Cu(0)s(2)O(9), the CuO6 octahedra show a characteristic Jahn-Teller distortion. Both, Ba3CuOs2O9 and Ba3ZnOs2O9, are electrically insulating. Magnetic and specific heat measurements confirm that Ba(3)Cu(0)s(2)O(9) is antiferromagnetically ordered below 47 K. Analysis of the magnetic data indicated that its magnetic properties are dominated by Cu2+ ions. The magnetic susceptibility of Ba3ZnOs2O9 is weakly temperature-dependent with a broad maximum 280 K, indicating the presence of strong exchange interactions within the Os2O9 dimer. The residual magnetic susceptibility at low temperatures also suggests the presence of appreciable exchange coupling between the dimers.
