Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 91: [MA] Poster II
O 91.1: Poster
Freitag, 30. März 2012, 11:00–14:00, Poster A
Inverse tunnel magnetoresistance with Mn2VGa based magnetic tunnel junctions — •Christoph Klewe, Markus Meinert, Jan Schmalhorst, and Günter Reiss — Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, 33501 Bielefeld, Germany
The ferrimagnetic Heusler compound Mn2VGa is predicted to have a pseudo-gap in the majority carriers [1], which should lead to inverse tunnel magnetoresistance. We synthesized epitaxial Mn2VGa thin films on MgO(001) substrates by dc magnetron co-sputtering, resulting in nearly stoichiometric films. XRD analysis revealed a mostly B2-ordered structure for the films deposited at substrate temperatures of 350∘C, 450∘C, and 550∘C.
Magnetic tunnel junctions with MgO barrier and CoFe counter-electrodes were fabricated. After post-annealing at up to Ta=400∘C negative TMR was obtained around zero bias, providing evidence for the inverted spin-polarization. Band structures of both electrodes were computed within the coherent potential approximation [2] and used to calculate the TMR vs. U characteristics, which are in good agreement with our experimental findings.
In addition, measurements on GMR-devices fabricated with Cu spacer layers were carried out. The current-in-plane GMR was negative as well, consistent with our TMR results.
[1] K. Özdogan, I. Galanakis, E. Sasioglu, B, Aktas, J. Phys.: Condens. Matter 18, 2905 (2006). [2] H. Ebert, D. Ködderitzsch, J. Minar, Rep. Prog. Phys. 74, 096501 (2011).