Dresden 2006 – scientific programme

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MA: Magnetismus

MA 3: Spin-Dependent Transport Phenomena I

MA 3.9: Talk

Monday, March 27, 2006, 12:15–12:30, HSZ 103

Interfacial microstructure of Fe/AlOx/Fe-magnetic tunnel junctions in high resolution — •Holger Schmitt¹, Jens Ellrich¹, and Horst Hahn^1,2 — ¹Forschungszentrum Karlsruhe GmbH, Institute for Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany — ²Technische Universität Darmstadt, Joint Research Laboratory Nanomaterials, Petersenstrasse 23, 64287 Darmstadt, Germany

Tunneling Magneto Resistance (TMR) systems were prepared by deposition of a Ta-buffered Fe-AlO_x-Fe-trilayer on a thermally oxidized Silicon wafer. In order to investigate the influence of the different Fe-oxides on the TMR effect, a ⁵⁷Fe tracer was deposited at the lower barrier interface. Using Conversion Electron Mössbauer Spectroscopy (CEMS) the chemical, structural and magnetic changes were followed from the as-prepared state and after several annealing steps. The nuclear probe technique can resolve different phases at the interface with submonolayer resolution. In addition, Transmission Electron Microscopy and X-Ray Reflectivity have been applied to complete the insight into the interfacial structure and to correlate to magnetoresistance of the trilayers. The results indicate the formation of a spinel-like phase and a spinel (Hycernite), in expense of the pure iron oxide Fe₂O₃, produced by a slight overoxidation of the barrier during its preparation. The changes at the interface are correlated to the changes of the TMR effect during annealing.