Frequency Modulation of a Nano-Oxide Layer-Based Spin-Torque Oscillator With FeCo Nanocontacts

We studied the effect of injecting a low-frequency (0.5-1 GHz) ac signal on the natural oscillations of a nano-oxide layer-based nanocontact magnetoresistive spin-torque oscillator with multiple Fe
₅₀
Co
₅₀
nanocontacts. We observed a frequency modulation effect with odd-numbered side bands having low amplitudes. Also, no frequency shift at main spectral peak's frequency, typical with nonlinear frequency modulation, was observed. We could not completely explain this behavior, but we propose that this could be related to the internal dynamics of constricted domain walls.