Dynamique d'aimantation dans les jonctions tunnels magnétiques à anisotropie perpendiculaire

Thu Nhi Tran Thi 1
1 NM - Nanostructures et Magnétisme
SP2M - UMR 9002 - Service de Physique des Matériaux et Microstructures : DSM/INAC/SP2M
Abstract : Epitaxial (MgO barrier) magnetic tunnel junctions (MTJs) are the most promising systems for applications ranging from high performance recording heads to magnetic random access memories (MRAM). Besides, such junctions also involves new and fascinating physics, such as the physics of electronic transport across epitaxial barriers, or the physics of magnetic coupling across a thin barrier. We described results obtained on MTJs perpendicular FePt/MgO/FePt magnetization. Far less studied, systems with perpendicular magnetization may have the highest potential for use at the highest recording densities in MRAM. We demonstrated that high magnetic anisotropy - L10 phase FePt layers can be grown in FePt/MgO/FePt trilayers, spontaneously with one soft and one hard layer. In addition, full magnetic decoupling is obtained in spite of the large magnetization of both layers. The manuscript then focuses on two studies. First, we observe the domain wall propagation speed on FePt single layers, as a function of both the applied field and of the layer thickness (from 2 to 6 nm), thereby extending the studies previously limited to ultrathin Pt/Co/Pt films to non-zero thicknesses. Second, we observed in details the magnetic coupling phenomena between the two FePt layers in full MTJs. By combining magneto-optical (macroscopic) studies and Magnetic Force Microscopy imaging, we gained a detailed understanding of the origin of the coupling, and of the process by which the cycling of the soft layer can induce a progressive demagnetization of the hard one.
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Thu Nhi Tran Thi. Dynamique d'aimantation dans les jonctions tunnels magnétiques à anisotropie perpendiculaire. Materials Science [cond-mat.mtrl-sci]. Université Joseph-Fourier - Grenoble I, 2009. English. ⟨tel-00967000⟩

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