Cationic ordering and role of the B-site lanthanide(III) and molybdenum(V) cations on the structure and magnetism of double perovskites Sr2LnMoO6

•Five new double perovskites of formula Sr2LnMoO6 were synthesized.•All the samples crystallize in the monoclinic P21/n space group.•Strong reducing conditions were used in order to stabilized Mo(V) cations.•A complete ordering between the rare earth and molybdenum ions was observed.•Magnetism agrees with the crystal distortions observed from Rietveld analysis.

We describe the preparation, crystal structure determination and magnetic properties of a new series of ordered double perovskite oxides Sr2LnMoO6 (Ln = Eu, Gd, Dy, Ho, Er, Yb) with Mo5+ and Ln3+ electronic configurations. These compounds have been obtained by solid state reaction under reducing conditions in order to stabilize Mo5+ cations. Structural characterization by XRPD and NPD was performed when Ln = Ho, Er, Yb and just XRPD for absorbing Ln = Eu, Gd, Dy. At room temperature, an excellent Rietveld fit was obtained for all the samples in a monoclinic symmetry, space group P21/n, with long-range ordering of Ln and Mo atoms. Magnetic susceptibility measurements show that some of these materials present magnetic ordering below 25 K and the determined effective magnetic moments are consistent with those expected for the pair Ln3+–Mo5+. All the phases have negative values​​ of the Weiss temperature indicating dominance of antiferromagnetic interactions.

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