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MA: Magnetismus
MA 3: Spin-Dependent Transport Phenomena I
MA 3.5: Vortrag
Montag, 27. März 2006, 11:15–11:30, HSZ 103
Co2FeSi an alternative for the Co2MnSi Heusler electrode integrated in magnetic tunnel junctions — •Daniel Ebke1, Ning-Ning Liu1, Marc Sacher1, Jan Schmalhorst1, Günter Reiss1, and Andreas Hütten2 — 1Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany — 2Forschungszentrum Karlsruhe GmbH, Institut für Nanotechnologie, Hermann-von-Helmholtz-Platz 1, D-76021 Karlsruhe, Germany
Recently, we have shown that the tunnel magnetoresistance of magnetic tunnel junctions containing the half metallic Heusler alloy Co2MnSi as lower magnetic electrode is limited to about 108% TMR-effect at 20K. This can be associated with the oxygen affinity of the Mn resulting in a MnSiOx- enriched layer at the tunnel barrier. To avoid this step like barrier we have started to integrate another Heusler alloy, Co2FeSi, as a magnetic electrode which is very promising due to its high Curie temperature of 1100K. In this presentation the evolution of the TMR-effect amplitude at room temperature is discussed as a function of preparation conditions and the width of the AlOx-tunnel barrier. We will present XAS measurements revealing the Vanadium diffusion through the Co2FeSi layer deteriorating the atomic order at the Co2FeSi/AlOx-interface. Thus, to enhance the TMR-effect MgO was tested as a new seed layer so as to avoid the Vanadium. In addition, multilayered Heusler electrodes consisting of {Co2MnSixnm/Co2FeSixnm}N have been prepared to increase the atomic ordering of the Co2FeSi compound. The resulting TMR-effect amplitudes will be shown as a function of temperature and will be discussed in combination with magnetic and XRD measurements.