STRUCTURAL AND ELECTRONIC-PROPERTIES OF THE MIXED CO RU PEROVSKITES AA'CORUO6 (A, A'=SR, BA, LA)

The compounds Sr2CoRuO6, SrLaCoRuO6, Ba2CoRuO6, and BaLaCoRuO6 have be en prepared and characterized by X ray powder diffraction and SQUID ma gnetometry. All but Ba2CoRuO6 crystallize as pseudo-cubic perovskites with a disordered arrangement of Co and Ru cations over the six-coordi nate sites. Ba2CoRuO6 adopts the hexagonal 6H perovskite structure wit h Co in the vertex-sharing octahedra and a random arrangement of Co an d Ru in the M(2)O(9) dimers. Frustration is apparent in the magnetic p roperties of each of these compounds at low temperatures, in contrast to the 6H perovskite Ba3CoRu2O9, which shows no structural disorder an d orders antiferromagnetically at 106 K. (C) 1995 Academic Press, Inc.