Self-Generation of Chaotic Solitary Spin Wave Pulses in Magnetic Film Active Feedback Rings

The chaotic self-generation of short solitary spin wave pulses has been observed for the first time. The pulses were produced from parametrically excited spin waves in an yttrium-iron-garnet film in an active feedback ring under conditions where both three-wave and four-wave parametric processes were allowed. The power-frequency spectrum was broadband and chaotic.

Figure 1

Diagram of YIG film active feedback ring system.

Figure 2

Measured transmission versus frequency profiles (left panels) and computed spin wave dispersion curves of frequency versus wave number (right panels) for two values of the field $H$, as indicated. The vertical and horizontal lines and the $S$, $B$, $k_{\max }$, $\omega$, and $\omega /2$ labels mark band limits and frequency bands relevant to three- and four-wave processes.

Figure 3

Power-frequency spectra for different ring gain $G$ values, as indicated. The static field was 171 Oe, the same as in Fig. 2b.

Figure 4

Power-frequency spectrum development for frequencies close to that of the dominant ring mode at gain $G=0\mathrm{dB}$ as a function of the ring gain, as indicated. Graphs are shown for two frequency scales, 35 and 3.5 MHz, in order to show the simultaneous development of the four-wave ring mode frequencies (left graphs) and the fine structure and drive to chaos associated with the additional three-wave processes (right graphs).

Figure 5

Time trace envelope waveforms on a $30\mu \mathrm{s}$ time scale for two different ring gain $G$ values, as indicated. The left insets show corresponding power-frequency spectra. The right insets show expanded time traces.