Synthesis, structure and magnetic properties of La3Co2SbO9: A double perovskite with competing antiferromagnetic and ferromagnetic interactions

Abstract The synthesis, structural characterization, and magnetic properties of La 3 Co 2 SbO 9 double perovskite are reported. The crystal structure has been refined by X-ray and neutron powder diffraction data in the monoclinic space group P 2 1 / n . Co 2+ and Sb 5+ have the maximum order allowed for the La 3 Co 2 SbO 9 stoichiometry. Rietveld refinements of powder neutron diffraction data show that at room temperature the cell parameters are a =5.6274(2) A, b =5.6842(2)  A, c =7.9748(2)  A and β =89.999(3)°. Magnetization measurements indicate the presence of ferromagnetic correlations with T C =55 K attributed to the exchange interactions for non-linear Co 2+ –O–Sb 5+ –O–Co 2+ paths. The effective magnetic moment obtained experimentally is μ exp =4.38  μ B (per mol Co 2+ ), between the theoretical one for spin only (3.87  μ B ) and spin-orbit value (6.63  μ B ), indicating partially unquenched contribution. The low magnetization value at high magnetic field and low temperature (1  μ B /f.u., 5 T and 5 K) and the difference between ZFC and FC magnetization curves (at 5 kOe) indicate that the ferromagnetism do not reach a long range order and that the material has an important magnetic frustration.