  We consider the possibility to employ a quantum wire realized in a
two-dimensional electron gas (2DEG) as a spin ratchet. We show that a net spin
current without accompanying net charge transport can be induced in the
nonlinear regime by an unbiased external driving via an ac voltage applied
between the contacts at the ends of the quantum wire. To achieve this we make
use of the coupling of the electron spin to inhomogenous magnetic fields
created by ferromagnetic stripes patterned on the semiconductor heterostructure
that harbours the 2DEG. Using recursive Green function techniques we
numerically study two different setups, consisting of one and two ferromagnetic
stripes, respectively.
