High-frequency spin transfer nano-oscillator based on the motion of skyrmions in an annular groove

Abstract

Abstract Magnetic skyrmion-based spin transfer nano-oscillators (STNOs) have been proposed as microwave signal generators and attracted enormous interest recently. However, the oscillation frequency of skyrmion-based STNOs is about 2 GHz, which is not so high for practical applications. In this paper, we create an annular groove in the surface of the free layer and put skyrmions in the annular groove. Due to the potential of the groove, skyrmions are confined to moving in the groove when driven by the spin-polarized currents. Through micromagnetic simulations, it is found that the frequency tunability of the STNO with the presence of the annular groove reaches to 15.63 GHz, which is more than 6 times higher than the case without the presence of the annular groove because of three reasons: the oscillation radius of skyrmions can be adjusted by the groove, the potential of the groove is larger than that of the edge and the groove can limit the diameter of skyrmions so that a larger number of skyrmions can be placed in the groove. Our results present the understanding of dynamic of skyrmions in an annular groove, which provides alternative possibilities for the design of skyrmion-based STNOs.