  The influence of a spin-polarized current on long ferromagnetic nanostripes
is studied numerically. The current flows perpendicularly to the stripe. The
study is based on the Landau-Lifshitz phenomenological equation with the
Slonczewski-Berger spin-torque term. The magnetization behavior is analyzed for
all range of the applied currents, up to the saturation. It is shown that the
saturation current is a nonmonotonic function of the stripe width. For a stripe
width increasing it approaches the saturation value for an infinite film. A
number of stable periodic magnetization structures are observed below the
saturation. Type of the periodical structure depends on the stripe width.
Besides the one-dimensional domain structure, typical for narrow wires, and the
two-dimensional vortex-antivortex lattice, typical for wide films, a number of
intermediate structures are observed, e.g. cross-tie and diamond state. For
narrow stripes an analytical analysis is provided.

Mesoscale and Nanoscale Physics