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Theses

Tranport Tunnel Polarisé en Spin à l'Etat Solide

Abstract : This experimental Thesis investigates spin-polarized solid state tunneling between two ferromagnetic layers separated by an ultrathin insulating barrier, with an aim to bridge the gap between theory, which is based on ideal systems, and experiments dominated by junctions with amorphous barriers. The nearly total tunneling spin polarization of La0:7Sr0:3MnO3, when integrated into partially or fully epitaxial magnetic tunnel junctions, offers insight into the relationship between an insulating material's electronic structure and tunneling magnetotransport. In addition to transport experiments through epitaxial SrTiO3, Ce0:69La0:31O1:845, TiO2, MgO, and amorphous Al2O3, barriers, we have performed XMCD experiments on Al2O3 and MgO barriers to probe the theoretical underpinnings of our transport results. The half-metallic nature of La0:7Sr0:3MnO3 is then utilized inLa0:7Sr0:3MnO3/SrTiO3/La0:7Sr0:3MnO3 and La0:7Sr0:3MnO3/SrTiO3/Co junctions to quantitatively confirm the spectroscopic nature of spin-dependent solid state tunneling between ferromagnetic electrodes. These bias-dependent studies underscore the influence of interfacial spin wave generation on the ferromagnetic order of the manganate/insulator interface near its Curie point. Finally, we utilize electromigration to modify both the density of states and the potential profile of the interfaces. We show how harnessing this effect may lead to a device with bistable magnetotransport properties; and we examine within the Fowler-Nordheim tunneling regime the incidence of such junction modifications on the formation of quantized energy states within the barrier, and the perturbation of interlayer exchange coupling between the ferromagnetic electrodes.
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https://tel.archives-ouvertes.fr/tel-00003921
Contributor : Martin Bowen <>
Submitted on : Monday, May 24, 2004 - 7:24:42 PM
Last modification on : Monday, December 14, 2020 - 2:56:05 PM
Long-term archiving on: : Wednesday, November 23, 2016 - 4:30:22 PM

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  • HAL Id : tel-00003921, version 5

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Martin Bowen. Tranport Tunnel Polarisé en Spin à l'Etat Solide. Matériaux. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00003921v5⟩

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