We find that photoexcited electrons in an n-GaAs epilayer rapidly (< 50 ps) spin-polarize due to the proximity of an epitaxial ferromagnetic metal. Comparison between MnAs/GaAs and Fe/GaAs structures reveals that this coherent spin polarization is aligned antiparallel and parallel to their magnetizations, respectively. In addition, the GaAs nuclear spins are dynamically polarized with a sign determined by the spontaneous electron spin orientation. In Fe/GaAs, competition between nuclear hyperfine and applied magnetic fields results in complete quenching of electron spin precession.
@article{arxiv.cond-mat/0201350,
title = {Spontaneous Spin Coherence in n-GaAs Produced by Ferromagnetic Proximity Polarization},
author = {R. J. Epstein and I. Malajovich and R. K. Kawakami and Y. Chye and M. Hanson and P. M. Petroff and A. C. Gossard and D. D. Awschalom},
journal= {arXiv preprint arXiv:cond-mat/0201350},
year = {2009}
}
Comments
13 pages, 4 figures, in press, Phys. Rev. B Rapid Communications (2002)