A ferromagnetic skyrmion-based spin-torque nano-oscillator with modified edge magnetization

Abstract

Magnetic skyrmion-based spin-torque nano-oscillators (STNOs) have attracted significant interest because of their potential applications as microwave signal emitters and integrability in the existing CMOS process flow. However, the stable circular motion of the skyrmion in the nanodisk is affected by the Magnus force, which can destroy and annihilate the skyrmion at the nanodisk edge, thereby limiting the application of the maximum oscillation frequency. To overcome this problem, we investigated the influence of a modified magnetized structure at the edge of the nanodisk on the oscillation dynamics of skyrmions, in which the modified magnetized profile is acquired by local modification of the magnetic material parameters, and these skyrmions can move along the tilting magnetization formatted wall. It was found that the upper threshold for steady skyrmion oscillations can be improved by approximately two times compared to the standard structure without modified edge magnetization profiles. Based on the effective field analysis, we confirmed that the spatial distribution of the tilting moment at the edge layer changed the effective field distribution and caused a non-monotonic change in the upper threshold current with the modified region width. Our results may provide an optional route for designing future skyrmion-based STNOs with better performance in the communication and computing areas.