Synthesis, Structure and Properties of Several New Oxychalcogenide Materials with the General Formula A2O2M2OSe2 A = La-Sm, M = Fe, Mn)

摘要

We report the synthesis of a series of manganese-containing oxychalcogenides with general formula A2O2Mn2OSe2 (A = La, Ce, Pr) as well several new A2O2Fe2OSe2 materials (A = La-Sm). We report the structural, magnetic, and conduction properties of the manganese-containing materials: La2O2Mn2OSe2, Ce2O2Mn2OSe2, and Pr2O2Mn2OSe2. These materials are isostructural with La2O2Fe2OSe2, and are shown to undergo a phase transition on cooling, apparently related to displacement of oxide ions from the Mn2O~(2+) plane. Peak splitting has been observed in the Pr~(3+) containing material at low temperatures, consistent with a reduction to orthorhombic symmetry. All of the manganese containing materials order antiferro-magnetically on cooling with k = (0, 0, 0), T_N = 164-184 K, and have a 12 K Mn~(2+) moment of around 4μ_B. The magnetic structure of La2O2Co2OSe2 is also reported. Conductivity studies have shown that La2O2Mn2OSe2 and La2O2Co2OSe2 are both semiconducting, with activation energies of ～0.24 and 0.35 eV.