Electronic and magnetic structures and conductivity of strontium ferrite: An ab initio LSDA + U approach
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Using the first-principle nonempirical linear muffin-tin orbital method in the tight-binding approximation (TB-LMTO) to the LSDA + U approximation, the electronic and magnetic structures and defect formation in strontium ferrite Sr3Fe2O6 are studied. It is found that Sr3Fe2O6 is a G type antiferromagnetic with the semiconductor electronic structure. The calculated band gap of 1.82 eV agrees well with experimental value (∼2 eV). The ferrite spectrum corresponds to that of a semiconductor with a band gap of charge transfer. Iron ions in Sr3Fe2O6 are in a high-spin state and have configuration t 2g ↑3 e g ↑2 e g ↓1 . The calculated local magnetic moment on the iron ions is 3.9 μB. The presence of iron ions with a magnetic moment approaching 4 μB in Sr3Fe2O6 is explained by strong hybridization of 3d orbitals of iron and 2p orbitals of oxygen. The high-spin state of iron ions is described by d 5 + d 6 L states with predominant contribution d 6L, where L is a hole on oxygen. Based on ab initio LSDA + U calculations, various types and configurations of defects in the oxygen sublattice (oxygen vacancies, anti-Frenkel defects) are studied and a model for ionic transport in Sr3Fe2O6 is proposed.
Key wordsstrontium ferrite ab initio calculations electronic structure defects
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