LaAMnSnO6 (A = Sr, Ba) have been synthesized by high temperature solid-state reactions under dynamic 1% H2/Ar flow. Rietveld refinements on room temperature powder X-ray diffraction data indicate that LaSrMnSnO6 crystallizes in the GdFeO3-structure, with space group Pnma and, combined with transmission electron microscopy, LaBaMnSnO6 in Imma. Both space groups are common in disordered double-perovskites. The Mn3+ and Sn4+ ions whose valence states were confirmed by X-ray absorption spectroscopy, are completely disordered over the B-sites and the BO6 octahedra are slightly distorted. LaAMnSnO6 are ferromagnetic semiconductors with a T C = 83 K for the Sr- and 66 K for the Ba-compound. The title compounds, together with the previously reported LaCaMnSnO6 provide an interesting example of progression from Pnma to Imma as the tolerance factor increases. An analysis of the relationship between space group and tolerance factor for the series LaAMnMO6 (A = Ca, Sr, Ba; M = Sn, Ru) provides a better understanding of the symmetry determination for double perovskites.
All Science Journal Classification (ASJC) codes
- Materials Chemistry