Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 23: Spinelectronics/ Spininjection in Heterostructures
MA 23.1: Vortrag
Mittwoch, 27. Februar 2008, 16:45–17:00, H 1028
First-principles calculations of the spin-orbit effects in a Fe/GaAs interface — •Martin Gmitra1, Alex Matos-Abiague1, Claudia Ambrosch-Draxl2, and Jaroslav Fabian1 — 1University of Regensburg, 93040 Regensburg, Germany — 2University of Leoben, A-8700 Leoben, Austria
The recently discovered tunneling anisotropic magnetoresistance(TAMR) effect in semiconductor heterostructures containing a single ferromagnetic layer is potentially useful for spintronics devices. TAMR essentially means that the tunneling current depends on the direction of the magnetization of the ferromagnet; if strong enough, this anisotropy can give a nice spin-valve-like signal. Important, TAMR has recently been observed in a metallic system, namely, in Fe/GaAs/Au junctions. Surprisingly, while all the bulk components of the system are cubic, the observed anisotropy is twofold, of the C2v class. This suggests that rather than coming from the bulk anisotropy of the density of states, the effect arises from the interface that indeed has a reduced symmetry. A phenomenological model reflecting this symmetry in the form of the Bychkov-Rashba and the Dresselhaus spin-orbit coupling was proposed, giving a quantitative fit to the experiment. Here we report on comprehensive ab initio calculations of the spin-orbit effects stemming from the interface anisotropy, providing strong support to the phenomenological theory. In particular, we have performed FLAPW density functional calculations of an Fe/GaAs slab to extract quantitative information about the proposed model as well as to provide guidance to future experiments.