Professor John Gregg

Abstract:

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

Abstract:

Magnonic circuit elements generally operate using signals that are either amplitude or phase modulated. We propose a simple all-magnon circuit element capable of converting between these two types of encoding, and support our design with simulations. We highlight the potential of our technique to augment existing devices and propose an alternative schematic for an “equality” gate and exclusive nor gate.