Two Problems in Spin-dependent Transport in Metallic Magnetic Multilayers

Transport properties of magnetic multilayers in current perpendicular to the plane of the layers geometry are defined by diffusive scattering in the bulk of the layers, and diffusive and ballistic scattering across the interfaces. Due to the short screening length in metals, layer by layer treatment of the multilayers is possible, when the macroscopic transport equation (Boltzmann equation or diffusion equation) is solved in each layer, while the details of the interface scattering are taken into account via the boundary conditions. Embedding the ballistic and diffusive interface scattering in the framework of the diffusive scattering in the bulk of the layers is the unifying idea behind the problems addressed in this work: the problem of finding the interface resistance in the multilayered structures and the problem of current-induced magnetization switching. In order to find the interface resistance, the method of solving the semiclassical linearized Boltzmann equation in CPP geometry is developed, allowing one to obtain the equations for the chemical potential everywhere in the multilayers in the presence of specular and diffuse scattering at the interfaces, and diffuse scattering in the bulk of the layers. The variation of the chemical potential within a mean-free path of the interfaces leads to a breakdown of the resistors-in-series model which is currently used to analyze experimental data. While the resistance of the whole system is found by adding resistances due to the bulk of the layers and resistances due to the interfaces, the interface resistances are not independent of the properties of the bulk of the layers, particularly, of the ratio of the layer thickness to the mean-free path in this layer. A mechanism of the magnetization switching that is driven by spin-polarized current is studied in noncollinear magnetic multilayers. Even though the transfer of the spin angular momentum between current carriers and local moments occurs near the interface of the magnetic layers, in order to determine the magnitude of the transfer one should calculate the spin transport properties far beyond the interfacial regions. Due to the presence of long longitudinal spin-diffusion lengths, the longitudinal and transverse components of the spin accumulations become intertwined from one layer to the