Vers l'Elaboration de Pistes Magnétiques Enregistrables : De la Molécule au Matériau

Abstract : Remarkable progress in information technology has led to the development of smaller and more powerful systems. This effort requires the design of new materials which are more complex at the atomic scale. Our goal is to develop magnetic nanoparticles confined into the well-organized nanocraters of non-magnetic thin films that should present a strong magnetic anisotropy (as oxides or alloys). In order to synthesize these magnetic nanoparticles, our original bottom-up approach involves three steps : i) elaboration of a solid nanostructured matrix via sol-gel chemistry in the presence of structuring agents, ii) formation of Prussian Blue Analogues (PBA) in the pores of this matrix and iii) thermal treatment under a controlled atmosphere. Two types of nanostructured matrices have been investigated : nanoperforated TiO2 thin films, in order to organize particles on a surface, and mesoporous silica monoliths, which allow to study the transformation of a larger amount of PBA nanoparticles into oxide or alloy than in the case of thin films. PBAs were chosen as precursors for the formation of magnetic particles because of their well-defined chemical composition and structure. PBA chemistry is versatile and the stoichiometry and structure of the resulting coordination polymer can be perfectly controlled at the atomic scale. Controlling PBA chemistry should thus enable us to finely tune the chemical composition and structure of the corresponding alloys and oxides and hence their magnetic properties.An original method, developed in our laboratory, results in well-confined PBA particles within the organized porosity of a mesoporous silica monoliths to form PBA/SiO2 nanocomposites. The thermal treatment of these nanocomposites under different controlled atmospheres was then investigated in order to get Oxide/SiO2 and Metal/SiO2 nanocomposites with a perfectly preserved mesoporosity and well-confined nanoparticles with controlled chemical composition, size and shape.The PBA formation inside the nanocraters of a TiO2 thin film is performed by successive immersions of the film in the PBA precursor solutions. A systematic study of each step of the synthesis leads to the formation of PBA particles within each nanoperforation in the thin film. Finally, the thermal treatment under different controlled atmospheres enabled the transformation of PBA particles into oxides or alloys inside the nanoperforations.
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Virgile Trannoy. Vers l'Elaboration de Pistes Magnétiques Enregistrables : De la Molécule au Matériau. Chimie inorganique. Université Paris-Saclay, 2015. Français. ⟨NNT : 2015SACLS209⟩. ⟨tel-01253610⟩

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