Microwave-assisted switching of microscopic rings: correlation between nonlinear spin dynamics and critical microwave fields

Phys Rev Lett. 2007 Nov 16;99(20):207202. doi: 10.1103/PhysRevLett.99.207202. Epub 2007 Nov 14.


We have studied the spin dynamics of microscopic permalloy rings at GHz frequencies. Increasing the irradiation power, we observe first nonlinear spin dynamics and second microwave-assisted switching (MAS). We explore the MAS phase diagram as a function of microwave power and frequency f and, in particular, extract the critical microwave field hc(f). Its frequency dependence reflects characteristic eigenfrequencies from both the linear and nonlinear spin-wave spectrum. By comparing hc(f) with the different susceptibilities, we gain insight into the microscopic processes which might be the basis of a predictive theory of MAS.