Electronic and Magnetic Structures of Chain Structured Iron Selenide Compounds

TL;DR

This study uses first-principles calculations to analyze the electronic and magnetic structures of chain-structured iron selenide compounds, revealing complex magnetic interactions and proposing a unified magnetic model.

Contribution

It introduces a comprehensive first-principles analysis of Ce2O2FeSe2 and BaFe2Se3, and proposes an extended J1-J2-J3 model for their magnetic structures.

Findings

All compounds have non-quasi-1D electronic structures.

Antiferromagnetic exchange couplings are present between nearest-neighbor chains.

Magnetic ground states include ferromagnetic chains and block-AFM structures.

Abstract

Electronic and magnetic structures of iron selenide compounds Ce2O2FeSe2 (2212\ast) and BaFe2Se3(123\ast) are studied by the first-principles calculations. We find that while all these compounds are composed of one-dimensional (1D) Fe chain (or ladder) structures, their electronic structures are not close to be quasi-1D. The magnetic exchange couplings between two nearest-neighbor (NN) chains in 2212\ast and between two NN two-leg-ladders in 123\ast are both antiferromagnetic (AFM), which is consistent with the presence of significant third NN AFM coupling, a common feature shared in other iron-chalcogenides, FeTe (11\ast) and KyFe2-xSe2 (122\ast). In magnetic ground states, each Fe chain of 2212\ast is ferromagnetic and each two-leg ladder of 123\ast form a block-AFM structure. We suggest that all magnetic structures in iron-selenide compounds can be unified into an extended J1-J2-J3 model. Spin-wave excitations of the model are calculated and can be tested by future experiments on these two systems.