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.