New mixed valent ferrites (Tl{sub 1.5}Hg{sub 0.5})Sr{sub 3-x}Ba{sub x}Fe{sub 2}O{sub 9-{delta}} (O {le} x {le} 2) with the Tl-2212-type structure
- Universite de Caen (France); and others
A new series of layered ferrites (Tl{sub 1.5}Hg{sub 0.5})Sr{sub 3-x}Ba{sub x}Fe{sub 2}O{sub 9-{delta}} has been synthesized and characterized for the composition range 0 {le} x {le} 2. The structure has been refined from powder XRD data and shown to be similar to that of the tetragonal Tl-2212-type superconducting copper oxides. Electron diffraction and high-resolution electron microscopy studies reveal a regular stacking of the [(Tl, Hg)O], [(Sr, Ba)O] and [FeO{sub 2}] layers without defects of atomic ordering on both the (Tl, Hg) and (Sr, Ba) sites. Magnetic susceptibility measurements and {sup 57}Fe-Moessbauer spectroscopy have been performed for (Tl{sub 1.5}Hg{sub 0.5}) Sr{sub 2}BaFe{sub 2}O{sub 9-{delta}}. They provide evidence for antiferromagnetic ordering below 50 K with localized Fe{sup 3+} and Fe{sup 3+} and Fe{sup 4+} species at 4.2 K, while intermediate valence states due to electron delocalization between iron sites must be taken into account at 293 K. The role of mercury is discussed.
- OSTI ID:
- 569687
- Journal Information:
- Journal of Solid State Chemistry, Vol. 132, Issue 2; Other Information: PBD: Sep 1997
- Country of Publication:
- United States
- Language:
- English
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