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.

Figure optionsDownload as PowerPoint slide