Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 12: Spindependent Transport I
MA 12.8: Vortrag
Dienstag, 27. März 2007, 12:00–12:15, H22
Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions — •Andres Conca, Martin Jourdan, Christian Herbort, and Hermann Adrian — Institut für Physik, Johannes Gutenberg University, Staudinger Weg 7, 55128 Mainz, Germany
The full-Heusler compound Co2Cr0.6Fe0.4Al (CCFA) is expected to be a half metal, i.e. to show a 100% spin polarization at the Fermi energy. This property, together with the relatively high Curie temperature ( 800K) and the soft magnetic behaviour make CCFA a promising candidate for implementation in spinelectronic devices.
Magnetic tunneling junctions were deposited using epitaxial CCFA thin films as ground electrode with AlOx as barrier and Co as counter electrode. The use of an Fe buffer layer on MgO(100) induces the growth of highly ordered CCFA films with smooth surface even at low deposition temperatures, as proved by XRD, TEM and in-situ STM investigations. The CCFA films were additionally annealed at different temperatures up to 600oC. The dependence of the TMR ratio on the annealing temperature was studied. A maximum TMR ratio of 40.5% was measured from which a spin polarization of 54% is deduced by the Jullière model. Possible correlations between the TMR ratio and the surface properties, as observed with STM and RHEED, are discussed.
Alternatively, epitaxial CCFA films were also grown directly on MgAl2O4(100) and Al2O3(110). A comparison with the results on MgO substrates is shown.