First principles study on the electronic properties of rare-earth orthoferrites with a perovskite-type structure

Electronic properties of rare-earth orthoferrites, RFeO3 (R = rare earths) with optimized perovskite-type structures have been investigated systemically using the first principles method with a plane wave basis set. Ferromagnetic (FM) and antiferromagnetic (AFM) structures have been studied according to the different arrangements of magnetic moments of the Fe atoms. The results indicate that the AFM phase is more stable than the FM one at the normal temperature. The optimized structures of AFM phase are in good agreement with experiments. In both the FM and AFM phases, the magnetic moment of R atom is the same as that of the free R3+ ion. For the Fe atom, the magnetic moment in the FM phase is smaller than in the AFM one, and it decreases for both structures with increasing atomic number of R atom. For a given phase, the band structures with different R atoms are very similar. The most distinct difference between the band structures of the FM and AFM phases is that, a band gap exists at the Fermi level for AFM arrangement but not for the FM phase.