Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 2: Magnetische Dünne Schichten I

MA 2.3: Vortrag

Montag, 24. März 2003, 10:45–11:00, HSZ/04

Evolution of microstructural, magnetic and electrical properties of the Co₂MnSi Heusler alloy — •Sven Kämmerer, Sonja Heitmann, Andy Thomas, Daniela Sudfeld, Dirk Meyners, Andreas Hütten, and Günter Reiss — University of Bielefeld, Department of Physics, Universitätsstrasse 25, 33615 Bielefeld

The enhancement of the sensitivity of magnetoelectronic devices based on spin polarized films requires the search for full or at least higher spin polarized materials. One promising group of materials is the Heusler alloy Co₂MnSi. Although a 100% spin polarization has been theoretically predicted for this alloy, it remains to be seen to what an extend it can be realized in real spin valves or magnetic tunnel junctions. Hence the precise control over the microstructure of very thin Co₂MnSi films is essential. We applied a post annealing procedure to room temperature prepared samples based on a vanadium seed layer. Strong correlation between the annealing temperature and time is observed and an optimum set of preparation parameters can be extracted. Best samples show (110) texture accompanied by a saturation magnetization of about 3.8µ _B and relatively high coercitives of about 110Oe, both measured at room temperature. These optimized films are momentarily tested for applications in spin valve and magnetic tunnel junction systems. First experiments with polycrystalline Heusler Co₂MnSi thin films reveal a TMR (tunnel magnetoresistance) ratio of about 5% measured at room temperature. This value should be improved by using smoother films, by about a factor of two, prepared by post annealing.