Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 14: Magnetic Half Metals and Oxides

MA 14.3: Vortrag

Dienstag, 26. Februar 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)