Service de Physique de l'Etat Condensé

Spin polarized transport in artificial structures. Iron and aluminium oxides epitaxial growth
DSM/DRECAM/SPCSI - Oxides group logo_tutelle 

MBE growth of iron oxyde layers

Spin electronics is a new field of research which associates two domains of physics: magnetism and electronics. In the last decade, effects related to spin dependent transport like giant magnetoresistance (GMR) and tunnelling magnetoresistance (TMR) in magnetic heterostructures have stimulated a considerable interest. These physical properties can be exploited in a variety of advanced devices such as highly sensitive magnetic sensors (e.g. read heads for magnetic recording) and non volatile magnetic memories (MRAM). Some ferromagnetic oxides have a 100 % spin polarization (there are half metallic) and thus are promising candidates for applications in spin electronics. The use of half metallic ferromagnets electrodes in magnetic tunnel junctions (MTJs) can lead to TMR effects much higher than those obtained with usual ferromagnetic electrodes. One of the predicted half metallic oxide is magnetite Fe3O4 which exhibits a high Curie temperature (Tc= 858 K) so that one can expect the half metallic character to remain significant at room temperature.  

RHEED patterns of the α-Al2O3(0001) substrate and a 15 nm thick Fe3O4 film along the [1-100] direction of the substrate.

In this framework, we have developed an oxygen assisted molecular beam epitaxy (MBE) setup specially dedicated to the growth of oxides layers like Fe3O4, α-Fe2O3 or Al2O3 and MTJs like Fe3O4/Al2O3/F, where F is a ferromagnetic electrode (for example Fe, Co, or Fe3O4). The growth of each oxide layer is monitored in real time by reflection high energy electron diffraction (RHEED). Purity and stoichiometry of thin films are also checked in situ using X-ray photoemission spectroscopy (XPS).  

Vibrating sample magnetometer (VSM)

Some references: - “Structural properties of epitaxied nanometric iron oxide layers on α-Al2O3(0001): an in-situ RHEED study during growth”, S. Gota, E. Guiot, M. Henriot, M. Gautier-Soyer, Surf. Sci. 454-456, 796 (2000). - “Atomic-oxygen-assisted MBE growth of Fe3O4(111) on α-Al2O3(0001)(0001)”, S. Gota, J.-B. Moussy, M. Henriot, M.-J. Guittet, M. Gautier-Soyer, Surf. Sci. 482, 809 (2001). - “Magnetic properties of Fe2O3(0001) thin layers studied by soft X-ray linear dichroism”, S. Gota, M. Gautier-Soyer, M. Sacchi, Phys. Rev. B 64, 22407 (2001). - “Thickness dependence of anomalous magnetic behavior in epitaxial Fe3O4(111) thin films: Effect of density of antiphase boundaries”, J.-B. Moussy, S. Gota, A. Bataille et al, Phys. Rev. B 70, 174448 (2004). - “Crystalline γ-Al2O3 barrier for magnetite-based magnetic tunnel junctions”, A. M. Bataille, J.-B. Moussy, F. Paumieret al, Appl. Phys. Lett. 86, 012509-1 (2005). Collaborations: CEA/DSM/DRECAM/SPEC, Saclay CEA/DSM/DRFMC/SP2M, Grenoble CEA/DSM/DRECAM/LLB, Saclay CEA/DSM/DRFMC/SPINTEC, Grenoble CEMES-CNRS/Nanomat, Toulouse UMR CNRS/Thales, Palaiseau LNCMP, INSA-Toulouse  

Maj : 28/11/2005 (293)

 

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