Paul, A.K.; Reehuis, M.; Felser, C.; Abdala, P.M.; Jansen, M.: Synthesis, Crystal Structure, and Properties of the Ordered Double Perovskite Sr2CoOsO6. Zeitschrift für Anorganische und Allgemeine Chemie 639 (2013), p. 2421-2425
10.1002/zaac.201300429

Abstract:
Sr2CoOsO6, a new osmium based ordered semiconductor double perovskite was prepared by solid state synthesis from the respective binary oxides. Room temperature PXRD analysis shows the compound to be tetragonal [I4/m; a = 5.5503(1) Å and c = 7.9320(1) Å], whereas low temperature synchrotron data refinement has revealed a second monoclinic polymorph [I2/m; a = 5.4969(2) Å, b = 5.4979(2) Å, c = 8.0090(1) Å and γ = 90.527(1)°] with a fully ordered rocksalt arrangement of cobalt and osmium atoms over the perovskite B-sites. Heat capacity and magnetic measurements indicate that Sr2CoOsO6 shows antiferromagnetic ordering below TN = 108 K followed by a second magnetic transition at T2 = 65 K. It was shown that the change from the tetragonal to the monoclinic phase occurs at TN.