Abstract
We have studied a quinary Fe-based superconductor by the measurements of x-ray diffraction, x-ray absorption, Mössbauer spectrum, resistivity, magnetization, and specific heat. This apparently undoped oxyarsenide is shown to be self-doped via electron transfer from the ions. We observed successive magnetic transitions within the layers: an antiferromagnetic transition at 150 K followed by a weak ferromagnetic transition at 55 K. The spin orderings within the planes are discussed based on mixed valence of and .
- Received 1 September 2010
DOI:https://doi.org/10.1103/PhysRevB.82.104518
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