Single-crystalline nanopillars for spin-transfer measurements

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.