Seminarium Fizyki Materii Skondensowanej

We study a nonlinear spin dynamics of a ferromagnetic ring in a vortex state induced by the spin-polarized current. The spin dynamics of ferromagnets is commonly believed to be gyroscopic but we show that a response of the vortex-state ring to the spin-polarized current has hysteretic behaviour. We also found that the nonlinear spin oscillations are described by the simple and universal equation, known for many physical problems, like a point Josephson contact. We also suggest a design of a spin-transfer nano-oscillator (STNO) using the ferromagnetic ring as a free layer. Proposed nano-oscillator is characterised by the working frequencies up to 10 GHz, that makes it advantageous over the disc-based vortex oscillators operating in the sub-GHz range. Although the averaged output electromotive force vanishes, the output signal can be extracted with the help of special inhomogeneous analysers.