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Theses

Systèmes magnétiques dilués à base d'oxydes

Abstract : Following the report of a new kind of room temperature ferromagnetism in thin films of titanium oxide doped with cobalt, the research of analogous properties in bulk SrTiO3-based perovskite was considered. Solid solutions of SrTi(1-x)M(x)O(3-d) (M = Co, Fe ; 0.01 less or equal to x less or equal to 0.50) were prepared by substitution of cobalt or iron fot titanium; the oxygen stoechiometry was modified for some of these compositions by thermal treatment under low oxygen pressure. The magnetic properties of the two systems under study are very similar. All the compositions have a paramagnetic behavior; only in highly doped samples (x higher or equal to o.35) a transition to a spin glass state is show. A small ferromagnetic component was detected at low temperature in these high doped samples and associated with some ferromagnetic exchange interactions that can exist in the systems. In the weakly doped samples (x=0.01 and 0.02) a different small ferromagnetic signal was detected at room temperature; his evolution with the dopant concentration and oxygen stoechiometry was studied. The results suggest that the dopant may not be at the origin of the observed ferromagnetism. The highly doped samples show a semiconductor behavior with unexpected temperature dependence.
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https://tel.archives-ouvertes.fr/tel-00127088
Contributor : Claudia Decorse Pascanut <>
Submitted on : Monday, January 29, 2007 - 10:30:51 AM
Last modification on : Wednesday, October 14, 2020 - 4:00:11 AM
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  • HAL Id : tel-00127088, version 1

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Claudia Decorse Pascanut. Systèmes magnétiques dilués à base d'oxydes. Matériaux. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00127088⟩

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