Synthesis, structure and properties of the new layered manganese oxyselenide Sr2F2Mn2Se2O

•We have successfully synthesized a new layered manganese oxyselenide (SrF)2Mn2OSe2.•The resistivity (at 300 K) decreases three orders of magnitude than it of (BaF)2Mn2OSe2.•The large discrepancy between Ep and Es indicates its polaronic transport type.•The compound has strong frustrated magnetic correlation.•A short-range to long-range antiferromagnetic phase transition is observed at about 141 K.

Layered manganese oxyselenide Sr2F2Mn2Se2O was predicted from the stacking of the fluorite type block [Sr2F2]2+ alternating regularly with the anti-CuO2-type Mn2O square planar layer and successfully synthesized using solid state reaction under vacuum. The compound crystallizes in the layered tetragonal structure with I4/mmm space group and shows a semiconducting behavior. The large discrepancy between activation energy for conductivity, Eρ = 205 meV, and thermopower, ES = 41.7 meV, indicates its polaronic transport type. The compound has strong frustrated magnetic correlation, which gives rise to low-dimensional short-range ordering at high temperature with a small-angle canted antiferromagnetic (AFM) spin lattice. Furthermore, a short-range to long-range AFM phase transition is observed at about 141 K, in accord with the small heat capacity anomaly.