  The control of intrinsic magnetic degrees of freedom is very important as it
offers a practical means to manipulate and probe electron spin transport.
Tunable spin-orbit effect in quantum wires can in principle serve as a means to
achieve this goal. Here, we investigate within the scattering matrix approach
the effect of an in-plane magnetic field on the conductance of the quantum wire
in the Datta-Das geometry and show that the interplay of the spin-orbit
interaction with the magnetic field provides enhanced control over the electron
spin polarization. In particular, we predict a novel effect of magnetically
induced oscillations of the electron spin in a certain range of magnetic field.
