Berlin 2005 – scientific programme

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MA: Magnetismus

MA 13: Spinabh
ängiger Transport I

MA 13.1: Talk

Saturday, March 5, 2005, 10:45–11:00, TU EMH225

Interplay of atomic ordering and TMR-effect of Co₂MnSi Heusler electrodes in magnetic tunnel junctions — •Andreas Hütten, Sven Kämmerer, Jan Schmalhorst, and Günter Reiss — Department of Physics, University of Bielefeld, 33615 Bielefeld, germany

We have demonstrated that the full Heusler compound Co₂MnSi integrated as one of the magnetic electrodes in technological relevant MTJs is currently characterized by a maximum spin polarization of 66% at 20K. This limitation can mainly be associated with two experimental findings. Firstly, the formation of a step like barrier which is already created during plasma oxidation while preparing the AlO_x tunnel barrier and which is a direct consequence of the oxygen affinity of the Heusler elements Mn and Si. Secondly, it is difficult to avoid Co-Mn antisite formation at the Co₂MnSi AlO_x-barrier interface. The Co-Mn antisite formation has qualitatively been monitored using the normalized x-ray diffraction intensities of the Co₂MnSi superlattice reflections as a function of the resulting TMR-effect and has additionally been simulated by the intercalation of thin Co layers in between Co₂MnSi and AlO_x.