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Etude des propriétés structurelles locales des matériaux magnétorésistifs

Abstract : The aim of this work is to give an exhaustive characterization of
the local structure for two class of compounds: sodium doped
lanthanum manganites and tungsten doped iron-molybdenum
double-perovskites. Both class of materials usually behave as
conductors in the ferromagnetic phase and undergo a
metal-to-insulator transition, associated with a
ferromagnetic-to-paramagnetic(antiferromagnetic) transition, upon
varying the temperature or the doping level. It is widely accepted
that in manganites, as well as in double-perovskites, transport
properties are strongly influenced by the local structure (bond
lengths and angles) around key sites, occupied by magnetic ions. For
this reason the X-ray absorption spectroscopy (XAS), being sensitive
to the local order around the absorber atom, is the more suitable
technique to study such compounds. In this work, the local structure
of Na-doped manganites in the form of thin films has been studied as
a function of the film thickness, while, bulk samples of tungsten
doped iron-molybdenum double perovskite series have been
investigated to characterize the local structure as a function of
the doping level and to better understand the nature of the
metal-to-insulator transition. It was necessary to develop a TEY
detector. which realization was challenging from a technical point
of view and it required an extensive theoretical and technical work.
X-ray absorption measurements were done at the Italian beam line for
diffraction and absorption (GILDA-BM08) at the European Synchrotron
Radiation Facility (ESRF) of Grenoble (France).
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Contributor : Fabrizio Bardelli <>
Submitted on : Tuesday, April 3, 2007 - 4:16:23 PM
Last modification on : Thursday, June 18, 2020 - 12:46:02 PM
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Fabrizio Bardelli. Etude des propriétés structurelles locales des matériaux magnétorésistifs. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00139843⟩

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