Luminescence imaging of photoelectron spin precession during drift in   p-type GaAs
  Using a microfabricated, p-type GaAs Hall bar, is it shown that the combined application of co-planar electric and magnetic fields enables the observation at 50 K of spatial oscillations of the photoluminescence circular polarization due to the precession of drifting spin-polarized photoelec- trons. Observation of these oscillations as a function of electric field E gives a direct measurement of the minority carrier drift mobility and reveals that, for E = 800 V/cm, spin coherence is preserved over a length as large as 25{\mu}m. 
V. Notot, D. Paget, A. C. H. Rowe, L. Martinelli, F. Cadiz, and S.   Arscott
cond-mat.mes-hall