  Magnetization switching provoked by spin-injection is studied in Ni nanowires
of various size and morphology. The response of the magnetization to the
spin-injection is studied as a function of the amplitude of the current, the
temperature, and the symmetry of the interfaces. The amplitude of the response
of the magnetization to spin-injection is a decreasing function of the
temperature, does not depend on the current sign, and occurs only in the case
of asymmetric interfaces. It is shown that the spin-injection does not act on
small magnetic inhomogeneities inside the layer. Some consequences in terms of
longitudinal spin-transfer are discussed.
