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Theses

Etude des propriétés ferromagnétiques de (Ga,Mn)As par le biais de l'hydrogène

Abstract : Ga,Mn)As is a model material for spintronics, being both semiconducting and ferromagnetic, as the result of the exchange interaction between the spins of the manganese atoms (3d5-4s2), and those of the holes they bring to the matrix. Its Curie temperature (Tc) is typically situated between 50 and 150 K.
In order to decouple magnetic ([Mn]) and electrical doping (p), we used a hydrogen passivation technique to form electrically inactive (Mn,H) complexes. The different consequences of the incorporation of hydrogen in the layer were first established, considering magnetic properties (appearance of a paramagnetic phase), electronic structure (reduction of p), and structural effects on the lattice.
A series of samples of increasing doping was then fabricated using this process, for layers in tensile or compressive strain. A good agreement with mean field theory predictions was obtained concerning the evolution of the magnetic anisotropy and of Tc as a function of the carrier density and epitaxial strain.
The last study focused on magnetic domains, and the magnetization reversal mechanisms of continuous layers and single-domain structures with a perpendicular-to-plane easy axis. We developped a local passivation process using hydrogenation to pattern magnetically (Ga,Mn)As (minimum structure size ~ 200 nm). Among other results, this technique reduces the mean switching fields in arrays of micron-sized dots, compared to structures fabricated by the more traditionnal etching technique. Finally, preliminary results of domain wall propagation induced by a magnetic field or a spin-polarized current were obtained in stripes patterned by hydrogenation.
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https://tel.archives-ouvertes.fr/tel-00165545
Contributor : Laura Thevenard <>
Submitted on : Friday, July 27, 2007 - 4:24:44 PM
Last modification on : Monday, December 14, 2020 - 9:53:09 AM
Long-term archiving on: : Tuesday, September 21, 2010 - 1:17:27 PM

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  • HAL Id : tel-00165545, version 2

Citation

L. Thevenard. Etude des propriétés ferromagnétiques de (Ga,Mn)As par le biais de l'hydrogène. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2007. Français. ⟨tel-00165545v2⟩

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