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Physico-chimie de cobaltites à mono-couche de thallium de type 1222

Abstract : When located in a regular oxygen octahedron, Co3+ ions (3d6) generally exhibit a low spin configuration (S=0). However a simple model, based on the competition between exchange, correlation and crystal field effects, predicts than an elongation of the octahedron favors an intermediate spin (IS, S=1) or high spin (HS, S=2) states. Such a distortion has been previously reported in thallium cuprates having 1222 structure. Looking for these unusual spin configurations, a new compound Tl0.9Sr3LaCo2O8.6 could be prepared, using a critical elaboration process, and characterized. The IS/HS equilibrium together with the mixed valence Co3+ / 2+ were find to play an essential role in the electronic properties. The behavior of this new cobaltite is compared with those of other 2D Co oxides, especially on the basis of band structure computation.
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Submitted on : Tuesday, September 30, 2003 - 6:06:50 PM
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Sébastien Courjault. Physico-chimie de cobaltites à mono-couche de thallium de type 1222. Autre. Université Sciences et Technologies - Bordeaux I, 2002. Français. ⟨tel-00003446⟩

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