Dynamique de l'aimantation de nano-oscillateurs micro-ondes à transfert de spin

Abstract : This thesis addresses a current topic of spinelectronics which are steady-state oscillations of the magnetization induced by spin transfer torque. In magnetic nanostructures, the large oscillation amplitude is of interest since it allows probing of the magnetization dynamics in the non-linear regime but also for integrated microwave components. Here the small size of the devices and the relatively large frequency tuning range are promising properties for future telecommunications. However, before integration, major issues need to be addressed such as increasing the output power and understanding the spectral purity. Therefore, we studied experimentally the dynamic behaviour of two types of spin transfer oscillators. The first type focuses on a spin valve structure with a perpendicularly magnetized polarizing layer. We showed that large amplitude magnetization oscillations around its energy maximum can be established as a result of the perpendicular polarizer. With the help of micromagnetic simulations, we were able to interpret qualitatively the experimental results. The second type of structures are MgO based magnetic tunnel junction oscillators of large output power. We developed an experimental set-up to follow the magnetization dynamics in the time domain as well as a data processing protocol to analyze the spectral purity. We identified different transient processes limiting the coherence of the magnetic oscillations, in particular frequency fluctuations on tens of nanoseconds time-scale.
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Dimitri Houssameddine. Dynamique de l'aimantation de nano-oscillateurs micro-ondes à transfert de spin. Physique [physics]. Université Joseph-Fourier - Grenoble I, 2009. Français. ⟨tel-00466637⟩

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