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Phénomènes dépendants du spin dans des structures à un puits quantique CdMnTe à modulation de dopage de type-n

Abstract : The study of the electronic and magnetic properties of n-type modulation doped CdMnTe quantum well structures has allowed to investigate the sp-d exchange interaction between 2D electrons and localized magnetic moments of Mn2+ ions. Such exchange interaction realigns the electronic spin states leading to a giant Zeeman splitting which deeply modifies the optical and electronic properties of the semiconductor host. At low magnetic fields, the sp-d exchange interaction term can be successfully described by the mean-field approach. However, in the high magnetic field region, we observe that a zero effective Zeeman energy (EZ=0) does not necessarily imply a closing of the spin gap. Raman scattering and transport experiments indicate a repulsion between spin up and spin down Landau levels. A model based on an anticrossing of the spin split Landau levels permits an almost complete understanding of our data. The magnetic properties of the Mn2+ ion subsystem show an influence of the carrier presence. The Knight shift of the position of the EPR spectrum can be described by the mean field approach in the low magnetic field region. However, the mean field approach does not account for the large shift of the Mn2+ spin resonance observed at high magnetic fields in the vicinity of EMnZ=EeZ. A model based on a resonant interaction between the mean-field spin excitations for electrons and Mn2+ ions has been proposed in order to interpret the Raman and EPR experimental data. Finally, a study of the evolution of the optical response as a function of carrier density in modulation doped II-VI quantum well structures reveals a persistence of excitonic transitions for electron densities for which Fermi energy is comparable to the exciton binding energy. Our investigation leads to address the question whether such observations are characteristic of homogenous system or they involve a phase separation.
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https://tel.archives-ouvertes.fr/tel-00135854
Contributor : Francisco Jose Teran <>
Submitted on : Friday, March 9, 2007 - 11:38:59 AM
Last modification on : Thursday, January 11, 2018 - 6:14:42 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 11:28:16 PM

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Francisco Jose Teran. Phénomènes dépendants du spin dans des structures à un puits quantique CdMnTe à modulation de dopage de type-n. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2001. Français. ⟨tel-00135854⟩

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