Electronic structure and magnetic properties of Al‐doped Ca2Fe2O5 brownmillerite compounds

Abstract Polycrystalline Ca 2 Fe 2− x Al x O 5 ( x = 0‐1.4) samples were prepared by conventional solid‐state reactions. Their crystalline/electronic structures and magnetic properties were characterized in detail. Powder X‐ray diffraction analyses revealed that the samples crystallized in orthorhombic brownmillerite‐type structures with the occurrence of the Pcmn ‐ Ibm 2 phase separation in the region between x = 0.4 and 0.6. The results obtained from analyzing Raman scattering and X‐ray‐absorption fine‐structure spectra also indicated this phase separation. Although x in Ca 2 Fe 2− x Al x O 5 varies in a wide range from 0 to 1.4, the +3 oxidation state of Fe remained almost unchanged. Magnetization measurements revealed that all Ca 2 Fe 2− x Al x O 5 samples have weak ferromagnetic order, and both the saturation magnetization and coercive force are dependent on the temperature, x , and structure phases.