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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.