The currents in magnetic multilayers are spin polarized and carry enough angular momentum that they can cause magnetic reversal and induce stable precession of the magnetization in thin magnetic layers. The flow of spins is determined by the spin-dependent transport properties, like conductivity, interface resistance, and spin-flip scattering in the magnetic multilayer. When an electron spin carried by the current interacts with a magnetic layer, the exchange interaction leads to torques between the spin and the magnetization. The torque that results from this interaction excites the magnetization when the current is large enough. The qualitative features of the dynamics that result from the current-induced torques are captured by a simple model in which the magnetization of the layer is assumed to be uniform. Even greater agreement results when finite temperature effects are included and the magnetization is allowed to vary throughout the film.
Spin Dynamics in Confined Magnetic Structures III: Topics in Applied Physics 101