Structural and magnetic properties of Ba3La3Mn2W3O18

A quaternary phase, Ba₃La₃Mn₂W₃O₁₈, was synthesized in reduced atmosphere (5% H₂/Ar) at 1200 °C and characterized by using powder X-ray diffraction, electron diffraction and high resolution TEM. Ba₃La₃Mn₂W₃O₁₈ crystallizes in rhombohedral space group with the cell parameters, and , and can be attributed to the n=6 member in the B-site deficient perovskite family, A_nB_n−1O_3n. The structure can be described as close-packed La/BaO₃] arrays in the sequence of (hcccch)₃, wherein the B-site cations, W and Mn, occupy five octahedral layers in every six octahedral layers, which leave a vacant octahedral layers separating the 5-layer perovskite blocks. The B-cation layers in the perovskite block alternate along the c-axis in a sequence of W⁶⁺-Mn²⁺-W⁵⁺-Mn²⁺-W⁶⁺. The bond valence calculation and optical reflection spectrum confirm the presence of W⁵⁺. This compound behaves paramagnetically in wide temperature range and weak antiferromagnetic interaction only occurs at low temperatures.