Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 18: Poster I : Bio Magn. (1-2); Mag.Imgaging (3-9); Magn. Semiconductors (10-16); Half Metals & Oxides (17-20); Coupl.Phenomena (21-27); Magn. Mat. (28-41); Micro & Nanostr. Magn. Materials (42-61); Micro Magn. (62-64); Surface Magnetism (65-70); Transport Phenomena (71-85)
MA 18.83: Poster
Dienstag, 26. Februar 2008, 15:15–18:30, Poster E
Interface-dependent sign of tunneling magnetoresistance in CrO2/MgO/CoFe junctions — •Martin Sperlich1, Marcel Mathissen1, Titus Leo2, Christian Kaiser3, Hyunsoo Yang3, Stuart S. P. Parkin3, David J. Smith4, and Gernot Güntherodt1 — 1II. Physikalisches Institut, RWTH Aachen — 2School of Materials, Arizona State University, Tempe, USA — 3IBM Almaden Research Center, San Jose, USA — 4Department of Physics, Arizona State University, Tempe, USA
Half-metallic ferromagnets (FMs) such as CrO2 are potentially useful as electrodes in magnetic tunnel junctions (MTJs) because of the possibility for 100% spin polarization near the Fermi energy. We show the tunneling magnetoresistance (TMR) behavior of MTJs using epitaxial CrO2(100) as one electrode and a counterelectrode containing CoFe, with MgO as the tunnel barrier. When CrO2 is exposed to air, a few monolayers of the intrinsic surface decompose and negative TMR is observed. Conversely, sample surfaces protected by a thin Mg interlayer show small but positive TMR consistent with intrinsic spin polarization. Thus, the sign of the TMR can be reversed simply by subtle modifications to the CrO2/MgO interface. High resolution transmission electron microscopy confirms that we can remove the natively decomposed CrxOy layers by gentle Ar-ion sputtering and produce a good quality interface between MgO und CrO2.
T. Leo et al., APL 2007 (accepted).