Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 9: Poster 1

HL 9.113: Poster

Montag, 23. März 2009, 14:30–17:00, P2

Measurement of long spin lifetimes, spin diffusion and spin drift in n-doped GaAs — Andreas Maurer, •Roland Völkl, Andreas Einwanger, Tobias Korn, Mariusz Ciorga, Dieter Schuh, Dieter Weiss, Werner Wegscheider, and Christian Schüller — Universität Regensburg

On the road to spintronic devices it is crucial to develop materials with long spin lifetimes and to determine spin drift/diffusion lengths in these materials. The usual methods for measuring spin lifetimes are time resolved Kerr/Faraday rotation experiments, but this well established technique reaches its limits if the spin lifetime exceeds 10 ns.

Here, we report on Hanle-MOKE-measurements that show spin lifetimes far above 10 ns and mapping of spin drift and spin diffusion on the 50 µm scale. In the Spin-Hanle experiment[1], spins are injected with a circularly polarized CW-Laser and the net spin polarisation perpendicular to the sample plane is measured by detecting the Kerr rotation of a linearly polarized laser. By applying an external magnetic field the spins start to precess and the spin polarisation is reduced. This effect is stronger when the spin lifetime τ is longer. In both cases the width at half maximum of the signal is proportional to 1/τ

By focussing the two beams through an optical microscope and scanning the pump beam with a motorized mirror we can measure spin diffusion, and by applying electrical fields spin drift.

[1] Stephens et al, PRL 93, 097602 (2004)