  We show that a controllable dc magnetization is accumulated in a junction
comprising a quantum dot coupled to non-magnetic reservoirs if the junction is
subjected to a time-dependent spin-orbit interaction. The latter is induced by
an ac electric field generated by microwave irradiation of the gated junction.
The magnetization is caused by inelastic spin-flip scattering of electrons that
tunnel through the junction, and depends on the polarization of the electric
field: a circularly polarized field leads to the maximal effect, while there is
no effect in a linearly polarized field. Furthermore, the magnetization
increases as a step function (smoothened by temperature) as the microwave
photon energy becomes larger than the absolute value of the difference between
the single energy level on the quantum dot and the common chemical potential in
the leads.
