Coupling efficiency for phase locking of a spin transfer oscillator to a   microwave current
  The phase locking behavior of spin transfer nano-oscillators (STNOs) to an external microwave signal is experimentally studied as a function of the STNO intrinsic parameters. We extract the coupling strength from our data using the derived phase dynamics of a forced STNO. The predicted trends on the coupling strength for phase locking as a function of intrinsic features of the oscillators i.e. power, linewidth, agility in current, are central to optimize the emitted power in arrays of mutually coupled STNOs. 
B. Georges, J. Grollier, M. Darques, V. Cros, C. Deranlot, B.   Marcilhac, A. Fert, G. Faini