  Electronic transport through thin and laterally constrained domain walls in
ferromagnetic nanojunctions is analyzed theoretically. The description is
formulated in the basis of scattering states. The resistance of the domain wall
is calculated in the regime of strong electron reflection from the wall. It is
shown that the corresponding magnetoresistance can be large, which is in a
qualitative agreement with recent experimental observations. We also calculate
the spin current flowing through the wall and the spin polarization of electron
gas due to reflections from the domain wall.
