A57Fe Mössbauer Study ofREBa2Fe3O8+wTriple Perovskites with Varied Oxygen Content (RE=Dy, Er, and Y)
✍ Scribed by J Lindén; A Kjekshus; P Karen; J Miettinen; M Karppinen
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 355 KB
- Volume
- 139
- Category
- Article
- ISSN
- 0022-4596
No coin nor oath required. For personal study only.
✦ Synopsis
RE Ba 2 Fe 3 O 8؉w phases (RE ؍ Dy, Er, and Y) with a varied oxygen content (؊ 0.25 < w < 0.10 in general, widest for RE ؍ Dy, narrowest for RE ؍ Er) have been obtained by quenching from controlled atmospheres. The triple-perovskite-type structure is adopted for these phases, with two crystallographically different iron atoms, tetragonal above w+؊ 0.15 and orthorhombic below that oxygen content. The valence and spin states of iron are investigated using 57 Fe Mo¨ssbauer spectroscopy. At room temperature, an antiferromagnetic ordering is observed for all values of w. Six-and five-coordinated Fe 3؉ , S ؍ 5 2 environments are distinguished in the Mo¨ssbauer spectra and their occupancies for w ؍ 0 are in the exact structural ratio of these two coordinations. For w > 0, tetravalent iron (S ؍ 2) accompanies the extra oxygen atoms at the (originally) square-pyramidal Fe site, whereas divalent iron (S ؍ 2) accompanies the oxygen vacancies formed in the octahedral Fe site when w < 0. The latter splits into two components, the intensities of which correspond to the fractions of five-and four-coordinated iron with a random distribution of meridial oxygen vacancies in an octahedron.