Films ultraminces épitaxiés de MnFe2O4, CoFe2O4 et NiFe2O4 pour le filtrage de spin à température ambiante

Abstract : In spintronics, spin filtering is a physical phenomenon which has the potential to produce highly spin-polarized electron currents by the spin-selective transport of electrons across a ferromagnetic tunnel barrier. While spin filtering at room temperature is highly attractive for applications, the selection of materials having the necessary magnetic and electronic properties is quite limited. The insulating ferrites XFe2O4 (X= Co, Ni, Mn) whose Curie temperatures are well above 300 K are promising candidates for spin filtering at room temperature. In this thesis, I present an in-depth study of epitaxial MnFe2O4, NiFe2O4 and CoFe2O4 ultrathin films for room temperature spin filtering, by optimizing their crystalline growth by molecular beam epitaxy. The structural, chemical, magnetic and electrical properties were studied by a number of in situ and ex situ characterization techniques, demonstrating the potential of these oxides to act as magnetic tunnel barriers at room temperature. The spin filters were then integrated into tunnel junctions in order to perform spin-polarized tunneling transport experiments, involving either the Meservey-Tedrow technique or tunneling magnetoresistance (TMR) measurements. These experiments revealed for the first time the spin filtering capability of MnFe2O4(111) tunnel barriers and TMR effects were also observed at room temperature in nanometric tunnel junctions based on CoFe2O4(111) spin filter, showing the highest spin polarization value for a tunnel current at room temperature by spin filtering.
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Submitted on : Thursday, November 24, 2011 - 11:35:19 AM
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  • HAL Id : tel-00644352, version 1

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Matzen Sylvia. Films ultraminces épitaxiés de MnFe2O4, CoFe2O4 et NiFe2O4 pour le filtrage de spin à température ambiante. Science des matériaux [cond-mat.mtrl-sci]. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨tel-00644352⟩

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