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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.55: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Interface properties of the half-metallic Co₂MnSi — •Marc D Sacher¹, Daniel Ebke¹, Ning-Ning Liu¹, Andreas Hütten², Jan Schmalhorst¹, and Günter Reiss¹ — ¹Fakultät für Physik, Universität Bielefeld, D-33615 Bielefeld, Germany — ²Institut für Nanotechnologie, Forschungszentrum Karlsruhe GmbH, Germany

Halfmetallic ferromagnets are promising candidates as electrode material in magnetic tunnel junctions (MTJ). Because of their predicted spinpolarization of 100% one expects high tunnel magneto resistance (TMR) effects. With the Heusler alloy Co₂MnSi a TMR of currently 108% at 20K has been reached. This leads to a spinpolarization of 70%. The high TMR value strongly depends on the oxidation parameters of the adjacent alumina layer and the annealing temperature of the Co₂MnSi. Two mechanisms can explain this behavior. On the one hand there is found a Mn and Si diffusion to the electrode/ barrier interface and on the other hand a formation of MnO at the interface. We have investigated the stoichiometry and the element specific magnetization at the Co₂MnSi/ barrier interface with X-Ray absorption spectroscopy (XAS) and the magnetic circular dichroism (XMCD). We introduced thin interlayer (Co, Mn or Si) with varying thickness between the Heusler alloy and the tunnel barrier. Thus we can investigate in detail the influence of the three materials on the TMR as well as on the magnetic moment and the stoichiometry.