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

• Sr2CrOsO6 and Ca2CrOsO6 were prepared by solid state reaction.
• Both materials were shown to be ferrimagnetic insulators.
• Chemical pressure reduces the TC in contrast to effects in related double perovskite osmates.
• Complex canted antiferromagnetic structures were not found.

The ordered double perovskites Sr2CrOsO6 and Ca2CrOsO6 have been synthesized and characterized with neutron powder diffraction, electrical transport measurements, and high field magnetization experiments. As reported previously Sr2CrOsO6 crystallizes with R3¯ symmetry due to a−a−a− octahedral tilting. A decrease in the tolerance factor leads to a−a−b+ octahedral tilting and P21/n space group symmetry for Ca2CrOsO6. Both materials are found to be ferrimagnetic insulators with saturation magnetizations near 0.2 μB. Sr2CrOsO6 orders at 660 K while Ca2CrOsO6 orders at 490 K. Variable temperature magnetization measurements suggest that the magnetization of the Cr3+ and Os3+ sublattices have different temperature dependences in Sr2CrOsO6. This leads to a non-monotonic temperature evolution of the magnetic moment. Similar behavior is not seen in Ca2CrOsO6. Both compounds have similar levels of Os/Cr antisite disorder, with order parameters of η=80.2(4)% for Sr2CrOsO6 and η=76.2(5)% for Ca2CrOsO6, where η=2θ−1 and θ is the occupancy of the osmium ion on the osmium-rich Wyckoff site.

The ordered double perovskites Sr2CrOsO6 and Ca2CrOsO6 have been synthesized and characterized. Sr2CrOsO6 crystallizes with R3¯ symmetry due to a−a−a− octahedral tilting, while Ca2CrOsO6 (shown here) crystallizes with P21/n space group symmetry and a−a−b+ octahedral tilting. Both materials are ferrimagnetic insulators. Bending of the Cr–O–Os bonds in response to chemical pressure lowers the Curie temperature from 660 K in Sr2CrOsO6 to 490 K in Ca2CrOsO6.Figure optionsDownload as PowerPoint slide