We have studied the charge disproportionation phenomenon in CaFeO3 using the local-spin density approximation with the on-site Coulomb interaction parameter U and exchange parameter J. The calculation reveals that the total number of the 3d electrons is about 5.1 for both Fe(1)(Fe5+) and Fe(2)(Fe3+) atoms, and that there are about 0.25 electron holes in the O-2p band. Therefore, the charge disproportionation can be more accurately described as 2d5L(Fe4+)=d5L2(Fe5+)+d5(Fe3+), where L denotes a hole in the oxygen 2p band, instead of 2d4(Fe4+)=d3(Fe5+)+d5(Fe3+). The hybridization between the Fe-3d and O-2p orbitals is stronger for Fe(1) than for Fe(2) due to the shorter Fe(1)-O bond. The hyperfine magnetic field contributed from conduction electron polarization is larger for Fe(2), resulting from a stronger s-d hybridization between the s orbital of Fe(2) and the d orbitals of its neighboring Fe(1) atoms. The on-site Coulomb repulsion and the exchange interaction increase the splitting between the occupied spin up and unoccupied spin down bands of Fe atoms. Fe-3d electrons become localized and the occupied d-band shifts to a lower energy range, even below the O-2p level. The calculated magnetic moments, hyperfine fields, and electron charge density agree well with the experimental data.
J. Yang et al., "Study of the Electronic Structure of CaFeO₃," Journal of Applied Physics, American Institute of Physics (AIP), Jan 2005.
The definitive version is available at http://dx.doi.org/10.1063/1.1854275
Materials Science and Engineering
United States. Department of Energy
Keywords and Phrases
Antiferromagnetic Materials; Band Structure; Calcium Compounds; Density Functional Theory; Exchange Interactions (Electron); Hyperfine Interactions; Magnetic Moments
Article - Journal
© 2005 American Institute of Physics (AIP), All rights reserved.