  We use a combination of analytic calculations and numerical simulations to
demonstrate that electrical current flowing through a magnetic bilayer induces
dynamical coupling between the layers. The coupling originates from the
dependence of the spin transfer torque exerted on the layers on the relative
orientations of their magnetic moments. We demonstrate that such coupling
modifies the behaviors of both layers, significantly affecting the the
stability of the current-induced dynamical regimes and the efficiency of
current-induced magnetic reversal.
