A {sup 57}Fe Moessbauer study of the cubic perovskite-type phase LaBa{sub 2}Fe{sub 3}O{sub 8+w} ({minus}0.20 < w < 0.83)

Journal Article · Mon Jun 01 04:00:00 EDT 1998 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1998.7757· OSTI ID:642224

Linden, J ^[1]; Lippmaa, M; Karppinen, M ^[2]; Karen, P; Kjekshus, A ^[3]

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1. Aabo Akademi, Turku (Finland). Dept. of Physics
2. Helsinki Univ. of Technology, Espoo (Finland)
3. Univ. of Oslo (Norway). Dept. of Chemistry

Single-phase samples of LaBa{sub 2}Fe{sub 3}O{sub 8+w} with {minus}0.20 {le} w {le} 0.83 were synthesized, characterized by oxygen-content analyses, powder X-ray diffraction, and magnetic susceptibility, and investigated using {sup 57}Fe Moessbauer spectroscopy. At 296 K, antiferromagnetic ordering of the Fe sites was observed for samples having w {le} 0.45. When w {le} 0.45 0.0, the iron atoms occupy predominantly an Fe{sup 3+}, S = 5/2 state, the rest being Fe{sup 2+}, S = 2. For w {approx} 0, the intensities of the components in the Moessbauer spectra correspond to random distribution of oxygen vacancies around Fe{sup 3+}. When 0 {le} w {le} 0.45, increasing amounts of iron atoms enter the Fe{sup 4+}, S = 2 state. For w {ge} 0.45, which takes the paramagnetic state at room temperature, the amount of Fe{sup 4+} increases accordingly. At 85 K, there is inconclusive evidence of disproportionation of Fe{sup 4+} into Fe{sup 3+} and Fe{sup 5+} in the most oxidized w = 0.83 sample. The room-temperature Moessbauer data show that there occurs a gradual conversion from AF to P states with increasing w up to w {ge} 0.45, when all AF components simultaneously disappear. The room-temperature relationship between the average internal magnetic field and the oxygen content parameter w resembles the magnetic field vs temperature relationship for a cooperative magnetic material. The common mechanism is that both temperature and oxygen loading affect the ordered spin system.

• OSTI ID: 642224
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 138; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
CRYSTAL STRUCTURE
EXPERIMENTAL DATA
IRON OXIDES
LANTHANUM OXIDES
MAGNETIC SUSCEPTIBILITY
SPECTROSCOPY
STOICHIOMETRY
X-RAY DIFFRACTION