Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 6: Invited Talks Hehn / Eimüller
MA 6.1: Hauptvortrag
Montag, 23. März 2009, 14:00–14:30, HSZ 04
Symmetry dependent spin injection from Fe/MgO in single crystal based magnetic tunnel junctions — •Michel Hehn1, Fanny Greullet1, Julien Bernos1, Coriolan Tiusan1, Christine Bellouard1, Francois Montaigne1, Daniel Lacour1, Marc Alnot1, Yuan Lu1, Gwladys Lengaigne1, David Halley2, and Wolfgang Weber2 — 1LPM, Vandoeuvre les Nancy (France) — 2IPCMS, Strasbourg (France)
The transport in crystalline magnetic tunnel junctions (MTJ) attracted the interest of the international community after the theoretical predictions of Butler et al of giant tunnel magnetoresistance (TMR) effects. In these model systems the electrons are classified with respect to the symmetry of their associated electronic Bloch wave function. The large predicted TMR ratio is related to a symmetry dependent attenuation rate within the MgO single crystal barrier combined with a half metallic property of a specific symmetry in the Fe electrode. After a brief introduction to the physics of the transport in Fe/MgO/Fe MTJ, I will show how to exploit the symmetry dependence of the tunnel conductivity to engineer novel MTJs functionalities. We demonstrate that, a suitably chosen Cr(001) epitaxial metallic spacer layer quenches the transmission of particular electronic states, therefore acting as an additional symmetry dependent tunnel barrier for electrons at the Fermi level. Moreover, we show that this ultrathin Cr metallic barrier can promote quantum well states in an adjacent Fe layer. These results confirm the transport mechanism proposed by Butler et al. Extension to other materials will also be discussed.