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

Abstract

Forward volume spin waves were excited in a yttrium–iron–garnet film using a microstrip delay line. Low frequency modulations in output power were captured on a digital oscilloscope for various combinations of microwave input frequency and power. Using the decrease in mutual information as a criterion, an embedding delay time was chosen for each time series. The method of false nearest neighbors was then used to calculate a minimal embedding dimension, D. Despite large changes in input frequency (4.4 GHz<f<4.6 GHz) and power (15.7 dBm<P<22.7 dBm), D⩽3 for each time series, indicating a low dimensional system. Finally, the information dimension, d, was estimated by computing the distance from a collection of reference 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 higher power levels or at frequencies close to an odd dipole gap.