Information dimension analysis of chaotic forward volume spin waves in a yttrium-iron-garnet thin film

Forward volume spin waves were excited in a yttrium-iron-garnet film using a microstrip delay line. Low frequency modulations in output power were cap tured on a digital oscilloscope for various combinations of microwave input frequency and power. Using the decrease in mutual information as a criteri on, an embedding delay time was chosen for each time series. The method of false nearest neighbors was then used to calculate a minimal embedding dime nsion, D. Despite large changes in input frequency (4.4 GHz < f < 4.6 GHz) and power (15.7 dBm < P < 22.7 dBm), D less than or equal to 3 for each tim e series, indicating a low dimensional system. Finally, the information dim ension, d, was estimated by computing the distance from a collection of ref erence points to their nearest neighbors. The distribution for d was found to be bimodal. When correlated with the input microwave power and frequency , it was found that values of d < 2 occurred close to the auto-oscillation threshold in the vicinity of an even dipole gap. d < 3 was observed at high er power levels or at frequencies close to an odd dipole gap. (C) 2000 Amer ican Institute of Physics. [S0021-8979(00)64608-X].