  We report on current-induced magnetization switching (CIMS) in single-
crystalline nanopillars. Fe(14 nm)/Cr(0.9 nm)/Fe(10 nm)/Ag(6 nm)/Fe(2 nm)
multilayers are deposited by molecular-beam epitaxy. The central Fe layer is
coupled to the thick one by interlayer exchange coupling over Cr. The topmost
Fe layer is decoupled (free layer). Nanopillars with 150 nm diameter are
prepared by optical and e-beam lithography. The opposite spin scattering
asymmetries of Fe/Cr and Fe/Ag interfaces enable us to observe CIMS at small
magnetic fields and opposite current polarity in a single device. At high
magnetic fields, step-like resistance changes are measured at positive currents
and are attributed to current-driven magnetic excitations.
