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Elaboration et étude des propriétés structurales, magnétiques, électriques et magnétocaloriques d’oxydes mixtes type Pérovskites

Abstract : Manganites of formula La0.67Ba0.33Mn1-xFexO3 and Pr0.67Ba0.33Mn1-xFexO3 were synthesizedby ceramic route and their structural and physical properties were studied. The samples exhibit aparamagnetic-ferromagnetic transition for Fe rate £ 10% (resp. 5%) for the La (resp. Pr) series,while a typical behavior of spin glass is observed beyond this rate. This ferromagneticparamagnetictransition is associated to a metallic-semiconductor transition and a semiconductorbehavior throughout the whole temperature range is observed when there is no ferromagnetictransition. The physical properties can be interpreted by the double exchange mechanism whichweakens for increasing rates of substitution. The metallic conduction is due to electron scattering(by phonon and grain boundaries), while the semiconductor character is due to the presence ofpolarons.Magnetocaloric study for Pr0.67Ba0.33MnO3, Pr0.67Ba0.33Mn0.95Fe0.05O3, La0.67Ba0.33MnO3 andLa0.67Ba0.3Mn0.95Fe0.05O3 shows that our materials are promising to be used in magneticrefrigeration technology.
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Mohamed Baazaoui. Elaboration et étude des propriétés structurales, magnétiques, électriques et magnétocaloriques d’oxydes mixtes type Pérovskites. Matériaux. Université de Grenoble; Faculté des Sciences de Monastir (Tunisie), 2012. Français. ⟨NNT : 2012GRENI106⟩. ⟨tel-01680813v2⟩

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