Current-driven magnetization reversal and spin-wave excitations in Co/Cu/Co pillars

Using thin film pillars similar to 100 nm in diameter, containing two Co la yers of different thicknesses separated by a Cu spacer, we examine the proc ess by which the scattering from the ferromagnetic layers of spin-polarized currents flowing perpendicular to the layers causes controlled reversal of the moment direction in the thin Co layer. The well-defined geometry permi ts a quantitative analysis of this spin-transfer effect, allowing tests of competing theories for the mechanism and also new insight concerning magnet ic damping. When large magnetic fields are applied, the spin-polarized curr ent no longer fully reverses the magnetic moment, but instead stimulates sp in-wave excitations.