  Spintronics devices rely on spin-dependent transport behavior evoked by the
presence of spin-polarized electrons. Transport through nanostructures, on the
other hand, is dominated by strong Coulomb interaction. We study a model system
in the intersection of both fields, a quantum dot attached to ferromagnetic
leads. The combination of spin-polarization in the leads and strong Coulomb
interaction in the quantum dot gives rise to an exchange field acting on
electron spins in the dot. Depending on the parameter regime, this exchange
field is visible in the transport either via a precession of an accumulated dot
spin or via an induced level splitting. We review the situation for various
transport regimes, and discuss two of them in more detail.
