Electronic structure of CaFe<sub>2</sub>O<sub>4</sub> with antiferromagnetic spin ordering

Abstract

The electronic structure of antiferromagnetic CaFe2O4 is calculated by using a generalized gradient approximation considering on-site Coulomb interaction between d-electrons (GGA+U). We found that the antiferromagnetic phase is the most stable among non-magnetic, ferromagnetic, and antiferromagnetic phases. With GGA+U, the band gap energy of CaFe2O4 is calculated to be ca. 1.9 eV. The lower conduction band consists of the Fe 3d states split into t2g and eg states by the octahedral FeO6 environment. The Ca 3d states distribute upper conduction bands. On the other hand, the valence band is mainly composed of the interaction between Fe 3d and O 2p states. The valence band maximum is approximately located at the Z-point and the conduction band minimum at the X-point. This means that antiferromagnetic CaFe2O4 is an indirect energy gap material. The absolute value of the magnetic moment at Fe sites is calculated to be 4.16 µB, which is very close to experimental values.