  The magnetic reversal by spin-polarized current of a magnetic junction
consisting of two ferromagnetic layers and a nonmagnetic spacer in between is
considered. Initially, the free layer is magnetized antiparallel to the pinned
layer by an external magnetic field. Under current flowing, a nonequilibrium
spin polarization appears in the free layer. The interaction between the
injected spins and the lattice leads to instability of the antiparallel
orientation at the high enough current density and to switching the free layer
to a state with magnetization parallel to one in the pinned layer. If the free
layer thickness and the external magnetic field strength are large enough, then
a nonuniform switching is favorable, so that only a part of the free layer near
the injector switches. Such a switching is accompanied with appearance of a
domain wall between the switched and non-switched regions. The domain wall can
oscillate around the equilibrium position with some natural frequency depending
on the external magnetic field.
