Synthesis and crystal structure of novel CaRMnSnO6 (R = La, Pr, Nd, Sm–Dy) double perovskites

Abstract

The CaRMnSnO₆ (R = La, Pr, Nd, Sm–Dy) double perovskites were prepared using a solid state reaction in evacuated sealed silica tubes at 1050–1100 °C. All compounds belong to the GdFeO₃-type structure (orthorhombic a : b : c ≈ √2a_p : 2a_p : √2a_p unit cell, space group Pnma, (a⁺b⁻b⁻) tilt system). The crystal structures were investigated by electron diffraction and high resolution electron microscopy and were refined from X-ray powder diffraction data for the R = La, Sm, Dy representatives (La: R_I = 0.030, R_P = 0.033; Sm: R_I = 0.030, R_P = 0.010; Dy: R_I = 0.033, R_P = 0.010). A disordered arrangement of the Ca and R cations over the A positions and Mn and Sn cations over the B positions was found in all cases. The small difference in charge and size between the Mn³⁺ and Sn⁴⁺ cations, the small degree of Jahn–Teller deformation of the MnO₆ octahedra, and the ac-plane orbital ordering type were proposed as possible reasons for the cation disorder on the B sublattice. The compounds demonstrate a spin glass behavior in the temperature range from 25 to 300 K.