Defects and Disorder in Magnetoresistive Double Perovskite A2FeMoO6 (A = Sr,Ba)
A2FeMoO6 (A = Sr, Ba) is a double perovskite having an ordered ferrimagnetic structure of Fe and Mo magnetic superlattices. The Fe and Mo atoms are ordered on alternating, corner-shared octahedral sites, however, the ordered array can have imperfections that are dependent upon synthesis conditions. Mössbauer spectroscopy was used to examine the local magnetic and structural environment around the Fe atoms giving insight into what type of imperfections were present in the Fe magnetic superlattice. Transmission Mössbauer spectroscopy was performed on polycrystalline samples with varying degrees of disorder using magnetic fields of 0 and 70 kOe. We were able to clearly resolve the iron nuclei with flipped magnetic moments (iron having a magnetic dipole moment parallel to the Mo magnetic dipoles), and associate the disorder in the structure with the different sites observed in the Mössbauer spectrum. The amount of disorder induced by various synthesis conditions was consistent with magnetization measurements that consistently show a lower than expected average magnetic dipole moment.
KeywordsExternal Magnetic Field Mossbauer Spectroscopy Isomer Shift Hyperfine Field Magnetic Dipole Moment
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