Onset of spin wave time-domain fractals in a dynamic artificial crystal
Abstract
We report on the first observation of an exact fractal pattern in the time-domain arising spontaneously from a dynamic artificial crystal (DAC). The all-magnon process occurs in a passive, unlithographed magnetic waveguide. The DAC was created by a standing spin wave of frequency fDAC in a region of nonlinear waveguide, resulting in a spatio-temporally periodic potential. The interaction of travelling spin waves of frequency f' with the DAC resulted in a series of new modes appearing in a comb with intervals f(0) = fDAC-f'. As H was increased a 1st pre-fractal pattern was observed with frequency interval f(1) = f(0)/2. Finally, the onset of a 2nd pre-fractal was observed with frequency interval f(2) = f(1)/2 = f(0)/4. The magnetic field dependence of the nonlinear signals effect matched that of the DAC. The fractal-like behavior was demonstrated for different values of f'.