Formation of High-Density Surface Spin-Wave Soliton Train

The propagation characteristics of solitary spin waves in an yttrium iron garnet waveguide were investigated using a vector network analyzer and a real-time oscilloscope. Frequency- and time-domain analyses of spin-wave waveforms revealed the transition from linear to nonlinear response regimes and identified the threshold excitation power required to establish a single spin-wave soliton. With sufficiently high excitation power, a single spin-wave soliton transformed into a stable soliton train when the excitation frequency was modulated within dipole gaps. The frequency characteristics of the soliton train varied with the duration of the excitation power signal. The different time segments of the waveforms suggested the presence of new spin-wave modes excited through the self-modulation instability process, providing valuable insights into the formation of high-density spin-wave soliton trains.