Bifurcation to chaos in auto-oscillations in circular yttrium-ion-garnet films

One of the most intriguing features of any nonlinear system is its dynamic evolution. Starting from the steady state the system evolves to a linear pe riodic motion and then experiences a series of "phase transitions" known as bifurcation which lead to a final chaotic state. In order to better unders tand the nonlinear behavior in magnetic systems, an experimental and numeri cal study of bifurcation to chaos in auto-oscillations at ferromagnetic res onance is presented. Experiments have been performed with thin circular iro n garnet films using perpendicular high-power ferromagnetic resonance. Taki ng the magnetic field as a variable parameter the bifurcation route to chao s has been investigated. The system has been modeled by the usual three mag netostatic mode interaction model derived from the macroscopic Hamiltonian. Along with the modeled signal, the time dependence of the complex Lyapunov exponent has been investigated for the three magnetostatic modes. The poss ibilities for controlling chaos with periodic perturbation have been studie d and the reason for desynchronization bursts is discussed. (C) 1999 Americ an Institute of Physics. [S0021-8979(99)39108-8].