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A new layered Cu-based oxychalcogenide Ba_3Fe_2O_5Cu_2S_2 has been synthesized and its magnetic and electronic properties were revealed. Ba_3Fe_2O_5Cu_2S_2 is built up by alternatively stacking [Cu_2S_2]~(2-) layers and iron perovskite oxide[(FeO_2)(BaO)(FeO_2)]~(2-)layers along the c axis that are separated by barium ions with Fe~(3+) fivefold coordinated by a square-pyramidal arrangement of oxygen. From the bond valence arguments, we inferred that in layered CuC h-based(Ch =S, Se, Te) compounds the +3 cation in perovskite oxide sheet prefers a square pyramidal site, while the lower valence cation prefers the square planar sites. The studies on susceptibility, transport, and optical reflectivity indicate that Ba_3Fe_2O_5Cu_2S_2 is an antiferromagnetic semiconductor with a Ne′el temperature of 121 K and an optical bandgap of 1.03 eV. The measurement of heat capacity from 10 K to room temperature shows no anomaly at 121 K. The Debye temperature is determined to be 113 K. Theoretical calculations indicate that the conduction band minimum is predominantly contributed by O 2p and 3 d states of Fe ions that antiferromagnetically arranged in FeO_2 layers. The Fe 3d states are located at lower energy and result in a narrow bandgap in comparison with that of the isostructural Sr_3Sc_2O_5Cu_2S_2.
A new layered Cu-based oxychalcogenide Ba_3Fe_2O_5Cu_2S_2 has been synthesized and its magnetic and electronic properties were revealed. Ba_3Fe_2O_5Cu_2S_2 is built up by alternative stacking [Cu_2S_2] ~ (2-) layers and iron perovskite oxide [(FeO_2) (BaO) (FeO_2) ] ~ (2-) layers along the c axis that are separated by barium ions with Fe ~ (3+) fivefold coordinated by a square-pyramidal arrangement of oxygen. From the bond valence arguments, we inferred that in layered CuC h-based (Ch = S, Se, Te) compounds the +3 cation in perovskite oxide sheet prefers a square pyramidal site, while the lower valence cation prefers the square planar sites. The studies on susceptibility, transport, and optical reflectivity indicate that Ba_3Fe_2O_5Cu_2S_2 is an antiferromagnetic semiconductor with a Ne’el temperature of 121 K and an optical band gap of 1.03 eV. The measurement of heat capacity from 10 K to room temperature shows no anomaly at 121 K. The Debye temperature is determined to be 113 K. Theoretical c alculations indicate that the conduction band minimum is predominantly contributed by O 2p and 3 d states of Fe ions that antiferromagnetically arranged in FeO_2 layers. The Fe 3d states are located at lower energy and result in a narrow bandgap in comparison with that of the isostructural Sr_3Sc_2O_5Cu_2S_2 .