Electronic structure of SrFe_1-x(Mn,Co)_xO_3-: A CPA case study

A new methodology is suggested for determining and using the Coulomb interaction parameter U(t(2g)), taking into account the different energy localizations of t(2g) and e(g) states in disordered transition metal perovskite-like oxides, based on the local spin density approximation with Coulomb interaction correction method and the coherent potential approximation. The adjustment of U(t(2g))'s relies on the best coincidence of the experimental and calculated maxima in X-ray absorption/reflection spectra at simultaneous demand for the calculated magnetic moments to closely correspond to their experimental values in cubic oxides SrFeO3, SrMnO3, and SrCoO3. Then, the obtained U's are utilized in order to construct the Green functions for calculating the electronic properties of strongly correlated perovskite-like solid solutions within the coherent potential method. The high efficiency of the proposed methodology has been demonstrated by a close coincidence of the experimentally observed and calculated X-ray emission/absorption spectra, magnetic moments, density of states at the Fermi level, and electronic conductivity in the disordered non-stoichiometric SrFeO3-delta, SrFe0.75Mn0.25O3-delta, and SrFe0.85Co0.15O3-delta phases. The composition SrFe0.85Co0.15O3-delta is proposed as a promising electrode material with enhanced characteristics of electric transport.