Auto-oscillation threshold and line narrowing in MgO-based spin-torque   oscillators
  We present an experimental study of the power spectrum of current-driven magnetization oscillations in MgO tunnel junctions under low bias. We find the existence of narrow spectral lines, down to 8 MHz in width at a frequency of 10.7 GHz, for small applied fields with clear evidence of an auto-oscillation threshold. Micromagnetics simulations indicate that the excited mode corresponds to an edge mode of the synthetic antiferromagnet. 
S. Cornelissen, L. Bianchini, G. Hrkac, M. Op de Beeck, L. Lagae,   Joo-Von Kim, T. Devolder, P. Crozat, C. Chappert, T. Schrefl