Electronic and Magnetic Structures of Chain Structured Iron Selenide Compounds

摘要

Electronic and magnetic structures of iron selenide compounds Ce2O2FeSe2(2212\ast) and BaFe2Se3(123\ast) are studied by the first-principlescalculations. We find that while all these compounds are composed ofone-dimensional (1D) Fe chain (or ladder) structures, their electronicstructures are not close to be quasi-1D. The magnetic exchange couplingsbetween two nearest-neighbor (NN) chains in 2212\ast and between two NNtwo-leg-ladders in 123\ast are both antiferromagnetic (AFM), which isconsistent with the presence of significant third NN AFM coupling, a commonfeature shared in other iron-chalcogenides, FeTe (11\ast) and KyFe2-xSe2(122\ast). In magnetic ground states, each Fe chain of 2212\ast isferromagnetic and each two-leg ladder of 123\ast form a block-AFM structure. Wesuggest that all magnetic structures in iron-selenide compounds can be unifiedinto an extended J1-J2-J3 model. Spin-wave excitations of the model arecalculated and can be tested by future experiments on these two systems.