The effect of chemical pressure on the structure and properties of A2CrOsO6 (A=Sr, Ca) ferrimagnetic double perovskite

Abstract The ordered double perovskites Sr 2 CrOsO 6 and Ca 2 CrOsO 6 have been synthesized and characterized with neutron powder diffraction, electrical transport measurements, and high field magnetization experiments. As reported previously Sr 2 CrOsO 6 crystallizes with R 3 ¯ symmetry due to a − a − a − octahedral tilting. A decrease in the tolerance factor leads to a − a − b + octahedral tilting and P 2 1 / n space group symmetry for Ca 2 CrOsO 6 . Both materials are found to be ferrimagnetic insulators with saturation magnetizations near 0.2 μ B . Sr 2 CrOsO 6 orders at 660 K while Ca 2 CrOsO 6 orders at 490 K. Variable temperature magnetization measurements suggest that the magnetization of the Cr 3+ and Os 3+ sublattices have different temperature dependences in Sr 2 CrOsO 6 . This leads to a non-monotonic temperature evolution of the magnetic moment. Similar behavior is not seen in Ca 2 CrOsO 6 . Both compounds have similar levels of Os/Cr antisite disorder, with order parameters of η =80.2(4)% for Sr 2 CrOsO 6 and η =76.2(5)% for Ca 2 CrOsO 6 , where η =2 θ −1 and θ is the occupancy of the osmium ion on the osmium-rich Wyckoff site.