A high-purity Sr2FeMoO6 sample was synthesized. According to Rietveld analysis of X-ray diffraction data the occupancy of Fe at its regular B site was 95.6% with the rest occupying the Mo site, i.e., the antisite of Fe. Despite this, according to 57Fe Mössbauer spectra 22% of the Fe atoms resided in a trivalent state having an extremely low internal field of ~2.8T even at 5K, whereas a typical 46-T field was seen for the main component, which was known to arise from mixed-valence FeII/III. Since the low-field FeIII species were totally invisible to probing by X-ray diffraction measurements, it was suggested that they were atoms located on antiphase boundaries. Magnetization measurements revealed a slightly lowered saturation magnetization (Ms) for the sample exhibiting the highest concentration of antiphase boundaries, as compared to samples with low concentration of antiphase boundary atoms. The two-Fe-atom-thick antiphase boundary layer consists of Fe atoms antiferromagnetically coupled to each other. The spins of the antiphase boundary layer atoms turned perpendicularly to an applied magnetic field, as observed by Mössbauer spectroscopy.

Observation of Antiphase Boundaries in Sr2FeMoO6. J.Lindén, M.Karppinen, T.Shimada, Y.Yasukawa, H.Yamauchi: Physical Review B, 2003, 68[17], 174415 (5pp)