  We study spin effects in the magneto-conductance of ballistic mesoscopic
systems subject to inhomogeneous magnetic fields. We present a numerical
approach to the spin-dependent Landauer conductance which generalizes recursive
Green function techniques to the case with spin. Based on this method we
address spin-flip effects in quantum transport of spin-polarized and
-unpolarized electrons through quantum wires and various two-dimensional
Aharonov-Bohm geometries. In particular, we investigate the range of validity
of a spin switch mechanism recently found which allows for controlling spins
indirectly via Aharonov-Bohm fluxes. Our numerical results are compared to a
transfer-matrix model for one-dimensional ring structures presented in the
first paper (Hentschel et al., submitted to Phys. Rev. B) of this series.
