A skyrmion-based spin-torque nano-oscillator with enhanced edge

The oscillation frequency of the circular skyrmion motion in a nanodisk increases with the driving current density. However, the skyrmion may be destroyed at the nanodisk edge when the driving current density is larger than a threshold, which leads to a maximum oscillation frequency that may not be enough for ultrahigh frequency applications based on skyrmions. In this work, a modified nanodisk structure, in which a skyrmion can be driven by a large current density, is proposed. Numerical simulations demonstrate that when the edge of a ferromagnetic nanodisk has enhanced perpendicular magnetic anisotropy, the upper threshold of the skyrmion oscillation frequency can be increased by 75% compared to the original structure without enhanced edge. Our results may be useful for overcoming the frequency limit of the skyrmion-based spin-torque oscillator, which utilizes the current-induced oscillation of a skyrmion as the source of microwave power.