  In this paper, we propose to control the strength of phase-locking between
two dipolarly coupled vortex based spin-torque nano-oscillators by placing an
intermediate oscillator between them. We show through micromagnetic simulations
that the strength of phase-locking can be largely tuned by a slight variation
of current in the intermediate oscillator. We develop simplified numerical
simulations based on analytical expressions of the vortex core trajectories
that will be useful for investigating large arrays of densely packed
spin-torque oscillators interacting through their stray fields.
