Boundary-free spin torque nano-oscillators based on ferrimagnetic skyrmions

Abstract

Skyrmion-based spin torque nano-oscillators have great potential as microwave signal generators in communication technology. In this work, we propose a spin torque nano-oscillator based on ferrimagnetic skyrmions, where the current-induced force can be easily balanced by the controllable Magnus force due to the ferrimagnetic nature, resulting in a stable motion around the edge of the area with applied current. The direction of such a motion is switchable by tuning the ferrimagnet across the compensation point. The oscillation frequency is found to rely on the magnetization and can exceed 1.5 GHz around the angular momentum compensation point. In contrast to previous proposals based on ferromagnetic or antiferromagnetic skyrmions, our ferrimagnetic nano-oscillator does not require a shaped magnetic working layer, thus suggesting that the ferrimagnet could be a potential platform for building oscillator arrays and studying interaction between them.