Berlin 2008 – scientific programme
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MA: Fachverband Magnetismus
MA 14: Magnetic Half Metals and Oxides
MA 14.3: Talk
Tuesday, February 26, 2008, 11:00–11:15, EB 202
Investigations of the Co2MnSi/MgO(001) heterojunction - Looking for half-metallicity — •Björn Hülsen1, Peter Kratzer2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin — 2Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg
Magnetic memory devices that exploit the tunneling magneto-resistance (TMR) effect depend crucially on the spin polarization of the electrode materials. Ferromagnetic half-metals make perfect electrodes leading to a (theoretically) infinite TMR ratio. The full Heusler alloy Co2MnSi is predicted to be half-metallic and has recently been integrated in a magnetic tunnel junction[1] where a high TMR value and huge spin polarization have been measured.
Here, we use density functional theory (DFT) calculations to model an epitaxially grown Co2MnSi/MgO(001) interface as potential TMR device. Different terminations of Co2MnSi (stoichiometric Co- and MnSi- and non-stoichiometric Mn- and Si- planes) and different registry with respect to the insulating barrier (Mg-top, O-top, bridge, and hollow site) are investigated. For all terminations the O-top site is the stable configuration whereas the bridge site is unstable. By investigating the electronic and magnetic properties we find that the existence of the spin gap depends strongly on the termination. In most cases it is closed by interface states but in one case the half-metallicity is preserved.
[1] M. Oogane et. al., J. Phys. D: Appl. Phys. 39 834 (2006)