A ferromagnetic skyrmion-based nano-oscillator with modified perpendicular magnetic anisotropy

Perpendicular magnetic anisotropy can be induced when the atoms orbital anisotropy in the ultrathin ferromagnetic layer is reflected. Here, we computationally study a ferromagnetic skyrmion-based nano-oscillator model with a composite structure, where the skyrmion dynamics is controlled by modifying perpendicular magnetic anisotropy. The proposed nano-oscillator structure has two concentric circular areas with different anisotropy coefficients. When the anisotropy of the inner area is larger than that of the outer area, the inner area can provide a repulsive force acting on the skyrmion, leading to the motion of skyrmion along with the edge of the inner circular area. Three cases of skyrmion motion are found for different anisotropy coefficients. We also study the effects of each anisotropy coefficients and current density on the frequency of the skyrmion-based nano-oscillator. Our results provide a promising method to modulate the frequency of future skyrmion-based nano-oscillators.