Electronic structure of CaFe₂O₄ with antiferromagnetic spin ordering

抄録

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 t_2g and e_g 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 µ_B, which is very close to experimental values.