Magnetically frustrated double perovskites: Synthesis, structural properties, and magnetic order of Sr₂BOsO₆ (B = Y, In, Sc)

Double perovskites Sr₂BOsO₆ (B = Y, In, and Sc) were prepared from the respective binary metal oxides, and their structural, magnetic, and electronic properties were investigated. At room temperature all these compounds crystallize in the monoclinic space group P2₁/n. They contain magnetic osmium (Os⁵⁺, t_2g³) ions and are antiferromagnetic insulators with Néel temperatures TN = 53 K, 26 K, and 92 K for B = Y, In, and Sc, respectively. Powder neutron diffraction studies on Sr₂YOsO₆ and Sr₂InOsO₆ showed that the crystal structures remain unchanged down to 3 K. The Y and In compounds feature a type I antiferromagnetic spin structure with ordered Os moments of 1.91 μ_B and 1.77 μ_B, respectively. The trend in TN does not simply follow the development of the lattice parameters, which suggests that d⁰ compared to d¹⁰ ions on the B site favor a somewhat different balance of exchange interactions in the frustrated Os⁵⁺ fcc-like lattice.