Spin-dependent photoelectron tunneling from GaAs into magnetic cobalt

Abstract

The spin dependence of the photoelectron tunnel current from free-standing GaAs films into out-of-plane magnetized cobalt films is demonstrated. The measured spin asymmetry ($A$), resulting from a change in light helicity, reaches $\ifmmode\pm\else\textpm\fi{}6%$ around zero applied tunnel bias and drops to $\ifmmode\pm\else\textpm\fi{}2%$ at a bias of $\ensuremath{-}1.6 \mathrm{V}$ applied to the GaAs. This decrease is a result of the drop in the photoelectron-spin polarization that results from a reduction in the GaAs surface-recombination velocity. The sign of $A$ changes with that of the cobalt magnetization. In contrast, $A$ is negligible on nonmagnetic gold films.