Current-driven excitations in magnetic multilayers: A brief review

In 1996, Berger and Slonczewski independently predicted that a large enough spin-polarized dc current density sent perpendicularly through a ferromagnetic layer could produce magnetic excitations (spin-waves) or reversal of magnetization (switching). In the past few years, both current-driven switching and current-driven excitation of spin-waves have been observed. The switching is of potential technological interest for direct 'writing' of magnetic random access memory (MRAM) or magnetic media. The spin-wave generation could provide a new source of dc generated microwave frequency radiation. We will describe what has been learned experimentally about these two related phenomena, and some models being tested to explain these observations. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.