  A recent experiment reports a non-local spin-signal that shows oscillatory
behavior as a function of gate voltage when the contacts are magnetized along
the direction of current flow, but not when they are magnetized perpendicular
to the current, in agreement with the predictions from a simple theory. In this
paper we first present a straightforward extension of this theory to include
the angular spectrum of electrons and the extended injecting and detecting
contacts. The results are in good agreement with those from a non-equilibrium
Green function (NEGF)- based model with contact parameters adjusted to fit the
experimental contact conductances. They also describe certain aspects of the
experiment fairly well, but other aspects deserve further investigation.
