Different routes to charge disproportionation in perovskites-type Fe oxides

الأصل · EN

Iron perovskites CaFeO₃ and La₀.₃₃Sr₀.₆₇FeO₃ show charge disproportionation, resulting in charge-ordered states with Fe³⁺:Fe⁵⁺ =1:1 and =2:1, respectively. We have made photoemission and unrestricted Hartree-Fock band-structure calculation of CaFeO₃ and compared it with La₀.₃₃Sr₀.₆₇FeO₃. With decreasing temperature, a gradual decrease of the spectral weight near the Fermi level occurred in CaFeO₃ as in La₀.₃₃Sr₀.₆₇FeO₃ although lattice distortion occurs only in CaFeO₃. Hartree-Fock calculations have indicated that both the breathing and tilting distortions are necessary to induce the charge disproportionation in CaFeO₃, while no lattice distortion is necessary for the charge disproportionation in La₀.₃₃Sr₀.₆₇FeO₃.