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The genesis of the electronic spectrum and magnetic properties of a high-temperature cubic phase of SrFeO3–δ with the disordered distribution of oxygen vacancies under the variation of their concentration has been studied in the coherent-potential approximation within the LDA + U formalism. Experimental tendencies of the fundamental electron-energy and magnetic characteristics in SrFeO3–δ under the variation of oxygen nonstoichiometry within the homogeneity region, 0 ≤ δ ≤ 0.5, have been described.

55Mn NMR spectra in the magnetically ordered state in Sr0.98La0.02MnO3 manganite have been obtained and the magnetic susceptibility has been measured. It has been shown that the microscopic phase separation into the antiferromagnetic matrix and ferromagnetic clusters, which can be presented as magnetic polarons, is observed in the long-range magnetic order region.

The electronic structure and magnetic properties of the high-temperature cubic phase of strontium ferrite SrFeO2.5 with the disordered location of oxygen vacancies have been calculated using the coherent potential method. The semiconductor character of the electronic spectrum of SrFeO2.5 is observed only at certain types of disordering of vacancies over the oxygen sublattice, which makes it possible to choose among structural models of the high-temperature phase proposed on the basis of experiments.

The results of synthesizing a new layered phase—nickel oxybismuthide LaO1−δNiBi in a series of superconducting oxypnictides—and its properties in the superconducting and normal states are reported. Although the temperature of the transition of this phase to the superconducting state, T c ∼ 4 K, is much lower than the value T c = 55 K reached at present in oxyarsenide SmO1−δFeAs, the similarity of the crystal structures and ρ(T) dependencies indicates that the mechanism responsible for the appearance of the semiconducting state is the same in lanthane oxybismuthide and samarium oxyarsenide.