Charge Disproportionation and Antiferromagnetic Order of Sr_3Fe_2O_7 : Condensed Matter: Electronic Properties, etc.

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The charge disproportionation and the magnetic properties of Sr_3Fe_2O_7, which has a double-layered perovskite structure, have been investigated. From ^<57>Fe Mossbauer measurements, the Neel temperature T_N and the critical temperature for the charge disproportionation reaction (2Fe^<4+> → Fe^<3+> + Fe^<5+>) are determined to be 120 K ± 2 K and 343 K ± 10 K, respectively. Above 343 K, spectra clearly show a Fe^<4+> singlet. The ^<57>Fe Mossbauer spectrum at 4.5 K under externally applied longitudinal magnetic field consists of four magnetically split components and is similar to the spectrum obtained from CaFeO_3 with a helical spin structure. With an increase of the external magnetic field, the relative intensity of the 2nd and 5th absorption peaks increases, which implies that the magnetic moments of Fe have a tendency to form a texture perpendicular to the direction of the external magnetic field.
社団法人日本物理学会の論文
2000-09-15