High-Frequency Current-Controlled Vortex Oscillations in Ferrimagnetic Disks

Recently it was shown that ferrimagnetic nanodisks support a magnetic vortex state that can oscillate at frequencies up to 30 GHz, suggesting that a ferrimagnetic free layer in a spin-torque-driven nanopillar oscillator would have a significantly higher frequency than the ferromagnetic oscillator. Here theory shows that a nanopillar spin-torque oscillator with a current perpendicular to the ferrimagnetic free-layer will indeed drive high-frequency vortex oscillations. This work indicates that it is feasible to construct ferrimagnetic spin-torque oscillators with frequencies increased tenfold, or more. Moreover, the Oersted field from the current provides enhanced frequency control.