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Statut |
Confirmé |
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Série |
SEM-BESSON |
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Domaines |
cond-mat |
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Date |
Mardi 16 Octobre 2012 |
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Heure |
10:30 |
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Institut |
IMPMC |
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Salle |
salle de conférence 4-etage,couloir 22-23 UPMC, 4 Place Jussieu |
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Nom de l'orateur |
Takano |
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Prenom de l'orateur |
Mikio |
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Addresse email de l'orateur |
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Institution de l'orateur |
Institute for Integrated Cell-Material Sciences Kyoto University |
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Titre |
Bafeo3, a ferromagnetic iron oxide |
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Résumé |
A small class of oxides containing iron in a high valence state of Fe4+ (d4) has been known. The most representative phase is SrFeO3 (SFO) crystallizing in the cubic perovskite structure (a = 3.850 Å). SFO and related oxides behave very differently from Fe2+- and Fe3+-oxides like FeO, Fe3O4, and LaFeO3 (LFO). All these Fe2+- and Fe3+-oxides are antiferromagnetic (or ferrimagnetic) insulators in their ground states, while the Fe4+-oxides commonly exhibit a shift toward metallicity and ferromagnetism. The specificity of Fe4+-oxides can be assigned to the fact that the effective charge transfer energy, Δeff, drastically drops from ~8eV for FeO and ~5.5eV for LFO to ~-3eV for SFO. The characteristics of “Fe4+”-oxides should thus result from interplay of Fe d electrons and O p holes.
Very recently we succeeded in preparing BaFeO3 (BFO) crystallizing in the cubic perovskite structure (a = 3.97106(1) Å). Physical characterization revealed that BFO has a spiral spin structure of the A-type below 111K but turns ferromagnetic with a large atomic moment of 3.5 μB/Fe on application of a small external field of ~0.3 T at 5 K (0.2 T at 77K). BFO is the very first Fe-oxide that shows ferromagnetism at ambient pressure. The magnetic transition temperature increases from 111K to more than 300K up to 40GPa.
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Numéro de preprint arXiv |
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Commentaires |
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Fichiers attachés |
- seminTanako2012.pdf (128270 bytes)
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