Giant magnetoresistance (GMR) effect in magnetic multilayers is a consequence of spin dependent scattering and spin dependent electronic structure. The effect describes the way in which magnetic structure of a system modifies its transport characteristics. An effect associated with GMR is the current-induced magnetic switching between different magnetic configurations (eg between parallel and antiparallel ones). This effect, in turn, describes the influence of electric current on magnetic configuration of the system. The magnetic switching may take place when electric current exceeds a certain critical value, and is due to absorption by the magnetic layer of a spin current component normal to the magnetization, which gives rise to spin-transfer torque.
The macroscopic description of current-perpendicular-to-plane (CPP) GMR has been recently extended to describe also the current induced magnetic switching (CIMS). Such a description is based on the classical spin diffusion equations for the distribution functions and on the relevant boundary conditions for the longitudinal and transverse components of the spin current in the situation of quasi-interfacial absorption of the transverse components in a magnetic layer. The torque is then expressed in terms of the usual parameters derived from the CPP-GMR experiments and additionally by the spin-mixing interfacial conductance. The spin transfer torque gives rise to magnetic switching phenomena and also may lead to transition to stationary precessional modes, which can occur when system parameters obey certain conditions.