Resistance of a domain wall in the quasiclassical approach

Starting from a simple microscopic model, we have derived a kinetic equation for the matrix distribution function. We employed this equation to calculate the conductance G in a mesoscopic F'/F/F' structure with a domain wall (DW). In the limit of a small exchange energy J and an abrupt DW, the conductance of the structure is equal to G_2d=4σ_↑σ_↓/ (σ_↑+σ_↓)L. Assuming that the scattering times for electrons with up and down spins are close to each other we show that the account for a finite width of the DW leads to an increase in this conductance. We have also calculated the spatial distribution of the electric field in the F wire. In the opposite limit of large J (adiabatic variation of the magnetization in the DW) the conductance coincides in the main approximation with the conductance of a single-domain structure G_1d=(σ_↑+σ_↓)/L. The account for rotation of the magnetization in the DW leads to a negative correction to this conductance. Our results differ from the results in papers published earlier.