  We study electron transport through single-electron spin-valve transistors in
the presence of non-local exchange between the ferromagnetic leads and the
central normal-metal island. The Coulomb interaction is described with the
orthodox model for Coulomb blockade and we allow for noncollinear lead
magnetization directions. Two distinct exchange mechanisms that have been
discussed in the literature are shown to be of comparable strength and are
taken into account on equal footing. We present results for the linear
conductance as a function of gate voltage and magnetic configuration, and
discuss the response of the system to applied magnetic fields.
