Linear and nonlinear spin dynamics in GdFeCo microdisks: a microfocused Brillouin light scattering study

Abstract GdFeCo is one of the most promising alloys in the emerging ferrimagnetic spintronics. While ferromagnetic resonance properties have been assessed in thin films of this critical material, a comprehensive investigation of magnetization dynamics is elusive. In this work, we report linear and nonlinear spin dynamics of lithographically defined GdFeCo circular microdisks, which are directly probed using microfocused Brillouin light scattering spectroscopy. At low rf excitation powers, only the fundamental resonance is observed in the frequency range of 4–5.5 GHz, whereas at higher powers, second and third harmonics emerge. The intensity of the fundamental mode scales linearly with excitation power, while the harmonic modes display pronounced nonlinear behavior. Furthermore, we have demonstrated tunable access to resonant and non-resonant mechanisms of harmonic generation via an externally applied magnetic field. The results offer additional potential of GdFeCo in low-damping wave-based spintronics technologies.