Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 13: Spinabh
ängiger Transport I
MA 13.10: Vortrag
Samstag, 5. März 2005, 13:00–13:15, TU EMH225
Orbital effects in spin-polarized tunneling thru SRO/STO/SRO — •Daniel Wortmann1, Kiyoyuki Terakura2, and Stefan Blügel1 — 1IFF, Forschungszentrum Jülich, D-52425 Jülich, Germany — 2Creative Research Initiative “Sousei”, Hokkaido University, Sapporo, Japan
We present ab-initio calculations of spin-polarized tunneling in a SrRuO3/SrTiO3/SrRuO3 three-layer junction where SrRuO3 is a ferromagnetic metal and SrTiO3 forms a insulating barrier. Both SrRuO3 and SrTiO3 crystallize in the Perovskite structure with nearly identical lattice constants. Thus epitaxial heterojunctions can be formed with a small tetragonal distortion off an ideal cubic structure. Employing the Landauer formula, the tunneling conductance was calculated within the framework of the DFT using the Green function FLAPW method. The Green function itself was obtained from an embedding approach to account for the semi-infinite leads attached to the tunneljunction. Due to the magnetic exchange splitting in SrRuO3, bands of different orbital character contribute to the tunneling current in the two spin channels. While the minority t2g-bands contribute strongly to the tunnel current, for the majority spin these states are only available in a small part of the two-dimensional Brillouin zone. Together with a filtering effect, which is explained in terms of the complex bandstructure of SrTiO3, this leads to a significant spin-polarization of the conductance. This cannot be directly linked to the spin-polarization of the density of states of the system, but rather is a consequence of the orbital character of the states.