  We investigate the Fano-Anderson model coupled to a large ensemble of spins
under the influence of an external magnetic field. The interaction between the
two spin systems is treated within a meanfield-approach and we assume an
anisotropic coupling between these two systems. By using a nonadiabatic
approach, we make no further approximations in the theoretical description of
our system, apart from the semiclassical treatment. Therewith, we can include
the short-time dynamics as well as the broadening of the energy levels arising
due to the coupling to the external electronic reservoirs. We study the spin
dynamics in the regime of low and high bias. For the infinite bias case, we
compare our results to those obtained from a simpler rate equation approach,
where higher-order transitions are neglected. We show, that these higher-order
terms are important in the range of low magnetic field. Additionally, we
analyze extensively the finite bias regime with methods from nonlinear
dynamics, and we discuss the possibility of switching of the large spin.
