Electrical Spin Detection in Fe/GaAs Heterostructures

Eric Garlid (Physics)

Advisors: Paul Crowell (Physics)

We report on the electrical detection of spin transport in lateral Fe/GaAs/Fe devices. Spin-polarized electrons are injected into n -GaAs through Schottky tunnel barrier contacts. The measurement is based on the detection of a non-equilibrium spin population using a “non-local” ferromagnetic detector through which no charge current flows. The potential at the detection electrode is sensitive to the relative magnetizations of the detector and the source, as observed in conventional spin valves. The second and equally important aspect of the measurement is the observation of a Hanle effect, which is the modulation and suppression of the spin valve signal due to precession and dephasing in a transverse magnetic field. The magnitude of the non-local signal is consistent with estimates of the spin polarization based on previous optical detection measurements. We model the field dependence of the non-local Hanle signal by considering spin precession, drift, diffusion, and relaxation. We show using optical measurements that the sign and magnitude of the detection signal are directly correlated with the spin polarization in the GaAs channel. These results therefore demonstrate a fully electrical scheme for spin injection, transport, and detection in a lateral semiconductor device.