A comparison between advanced time–frequency analyses of non-stationary magnetization dynamics in spin-torque oscillators

We report re`sults of different time–frequency analyses (Wavelet and Hilbert–Huang Transform (HHT)) of voltage measurements related to a spin-torque oscillator working in a regime of non-stationary dynamics. Our results indicate that the Wavelet analysis identifies the non-stationary magnetization dynamics revealing the existence of intermittent and independent excited modes while the HHT is able to accurately extract the time domain traces of each independent mode. Overall performance indicates a route for a complete characterization of time–frequency domain data of a STO, pointing out that the combined Wavelet-HHT methodology developed is general and can be also used for a variety of other different scenarios.