The electric conductivity of a laminated metal system (alternating magnetic and nonmagnetic layers)

A set of kinetic equations for the distribution functions of carriers differing both by the energy spectrum and by the spin projection is used to investigate the conductivity of a multilayer sample (alternating layers of magnetic (m) and nonmagnetic (_n) metals). The boundary conditions on the interlayer surfaces are derived in an approximation in which the surface scattering is divided into “specular” and “diffuse” scattering and is characterized by scattering parameters (reflection and transmission) which are related to each other by relations dependent on spin projections and on the type of spectrum. The problem on the longitudinal (with respect to the layers) current is treated; situations are analyzed in which the variation in conductivity due to the change of mutual orientation of magnetization in successive m layers from antiparallel to parallel may be of the order of the values of the conductivity proper (the so-called giant magnetoresistance effect). This is possible only in the case of thin (compared with the free path) n layers (in m layers, the ratios of the characteristic dimensions may be arbitrary) and in the mandatory presence of specular surface scattering. Results are given for different possible ratios of Fermi momenta of electron groups and for different fractions of specular and diffuse scattering. The possibility of realizing the effects of both signs is demonstrated.