Spin torque nano-oscillators based on isolated edge skyrmions in nano-pillars with perpendicular anisotropy.

• The oscillation frequencies of an edge skyrmion in circular nano-pillars are analytically derived. • The size of the sample to produce isolated edge skyrmion oscillation is relatively small. • The oscillation frequencies strongly depend on the eccentricity and the perimeter of the elliptical nanopillar. The magnetic skyrmions have received a lot of attention because they have potential applications in spin torque nano-oscillators. In this paper, we numerically and analytically study the dynamics of edge skyrmions in circular nano-pillar oscillators with perpendicular magnetic anisotropy (PMA) free layer and spin polarizer. Numerical simulations demonstrate that a steady edge skyrmion oscillation mode with GHz frequency can be driven by spin currents and magnetic fields. The oscillation frequencies in circular nano-pillars with different radius are analytically derived, which agrees well with the numerical results. In addition, the steady oscillations of edge skyrmions are also observed in elliptical nano-pillars, in which the oscillation frequencies strongly depend on the eccentricity and perimeter of the elliptical nanopillar. It is found that the oscillation frequency of this edge skyrmion can range from 1 GHz to 6.7 GHz. The line width is about 55 MHz. [ABSTRACT FROM AUTHOR]