  Spin dependent transport in a three-terminal graphene nanoribbon (GNR) is
investigated in presence of Rashba spin-orbit interaction. Such a
three-terminal structure is shown to be highly effective in filtering electron
spins from an unpolarized source simultaneously into two output leads and thus
can be used as an efficient spin filter device compared to a two-terminal one.
The study of sensitivity of the spin-polarized transmission on the location of
the outgoing leads results in interesting consequences and is explored in
details. There exist certain symmetry relations between the two outgoing leads
with regard to spin-polarized transport, especially when they are connected to
the system in a particular manner. We believe that the prototype presented here
can be realized experimentally and hence the results can also be verified.
