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Excitation et détection optiques de la dynamique de l’aimantation dans le semi-conducteur ferromagnétique (Ga,Mn)(As,P)

Abstract : Development of impulsional laser enhanced the study of the magnetization dynamic in the temporal domain (fs-ns) with optical techniques. In thin ferromagnetic films with a weak optical absorption, excitation and optical mechanisms are not yet fully understood. To increase our understanding, variations of magnetic parameters are required. To that end, the magnetic semiconductor like (Ga,Mn)(As,P) are a good choice due to their magnetic properties easily adjustable thanks to the coupling between magnetic and semiconductor properties. In this thesis, conditions for optimal excitations were established. Supposing a thermal excitation origin, we assessed the transient change of temperature and anisotropy constant. I also established the role of the optical absorption and dephasing due to the finite magnetic layer thickness in the spin-waves detection process. The observation of several spin-waves gave me the opportunity to assess the spin-stiffness constant as a function of phosphorus. On the contrary of theoretical prediction, I showed that the spin-stiffness hardly vary with the phosphorus concentration.
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  • HAL Id : tel-01269654, version 2

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Sylvain Shihab. Excitation et détection optiques de la dynamique de l’aimantation dans le semi-conducteur ferromagnétique (Ga,Mn)(As,P). Chimie-Physique [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2015. Français. ⟨NNT : 2015PA066548⟩. ⟨tel-01269654v2⟩

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