Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 5: Spindependent Transportphenomena I
MA 5.6: Vortrag
Montag, 25. Februar 2008, 11:30–11:45, H 0112
Investigation of MTJs with MgO / Al2O3 composite tunnelbarriers — •Oliver Schebaum, Andy Thomas, and Günter Reiss — Bielefeld University, Thin Films and Physics of Nanostructures, Universitätsstraße 25, 33615 Bielefeld
Recently, large tunneling magnetoresitances (TMR) ratios have been reported in magnetic tunnel junctions (MTJs) with cristalline MgO tunneling barriers. The TMR ratio of MTJs with tunneling barriers made of Al2O3 on the other side seems to be limited to a much lower value. This behavior is interpreted to be due to coherent tunneling in the case of MgO as the tunneling barrier.
We have investigated the TMR ratio of MTJs with tunneling barriers made of a MgO/Al2O3 bilayer system. The samples were fabricated using an automatic magnetron sputtering machine with a base pressure of 1 × 10−7mbar. The MgO layers were formed by RF-sputtering MgO, whereas the Al2O3 layers were fabricated by sputtering metallic aluminum and post oxidization utilizing a electron cyclotron plasma oxidization in pure Oxygen.
The dependence of the TMR ratio of the thickness of the MgO and Al2O3 layers has been investigeted and the results are compared to the highest TMR ratios with either single MgO or single Al2O3 tunneling barriers.