Electronic, magnetic properties and chemical bonding in layered oxychalcogenides Ca _4Fe _2Cu _2S _2O _6 and Ca _4Fe _2Cu _2Se _2O _6 from first principles calculations

摘要

The crystal structure, electronic, magnetic properties and inter-atomic bonding in recently synthesized five-component Fe-containing oxychalcogenides Ca _4Fe _2Cu _2Ch _2O _6, where Ch are S or Se, which unlike all other related materials contain Fe atoms in 2D perovskite-like oxide blocks (Ca _4Fe _2O _6), were probed by means of first-principle FLAPW-GGA calculations. We found that these materials can be characterized as antiferromagnetic ionic semiconductors, composed of alternating non-magnetic chalcogenide blocks (Cu _2Ch _2) and antiferromagnetic oxide blocks (Ca _4Fe _2O _6) with S-AFM spin configuration for Fe sublattice; the interaction between these building blocks is ionic. Moreover, our results reveal that for these materials the formation of natural multiple quantum wells can be expected - like it has been found for more simple four-component LnCuOCh phases. This feature (unique for five-component Fe-containing phases) originates from 2D density of states and quantum size effects in these layered materials.