Extended auto-oscillator equation and non-linear parameters of a synthetic ferrimagnet spin torque oscillator

Spin-Torque Oscillators (STOs) have promising application as high frequency electronic devices. However, the relatively large linewidth exhibited in STOs devices is a prohibitive for applications. Devices with coupled magnetic layers seem adapted to tackle this problem, as the additional coupling energy improves the magnetic stability of the layers, and therefore reduce the linewidth. Indeed, it was observed experimentally that the linewidth of an oscillating Synthetic Ferrimagnetic (SyF) free layer was one order of magnitude smaller than a single layer. This result motivates a theoretical study of coupled layers self-sustained oscillations in order to understand precisely their oscillation modes.