Spin polarized electron transmission into GaAs quantum well across Fe3O4: Optical spin orientation analysis

We study electron spin transmission mechanism across an Fe3O4/GaAs quantum well interface from complementary optical approaches, i.e., optical polarization analysis of electroluminescence and spin dependent photocurrent measurement under optical spin orientation. A spin polarization over 40% is demonstrated at 10 K, as estimated from the electroluminescence due to free exciton recombination in the quantum well under spin injection conditions. The bias dependence of spin dependent photocurrent, on the other hand, shows two marked peaks due to spin filtering effect of Fe3O4, providing information on the spin-split barrier structure of the magnetic insulator Fe3O4. These combined results clearly elucidate the mechanism of the high efficiency of spin injection across Fe3O4. (C) 2010 American Institute of Physics. [doi:10.1063/1.3509419]