Nonlinear multi-magnon scattering in artificial spin ice

Magnons, the quanta of spin waves, are bosons whose number does not need to be conserved in scattering processes. Microwave-induced parametric magnon processes, often referred to as Suhl instabilities, have been known to occur in magnetic thin films only, where quasi-continuous magnon bands exist. Here, we reveal the existence of such nonlinear magnon-magnon scattering processes and their coherence in ensembles of magnetic nanostructures known as artificial spin ice [1]. These systems show scattering processes akin to those observed in continuous magnetic thin films. We utilize a combined microwave and microfocused Brillouin light scattering measurement approach to investigate the evolution of their modes. Scattering events occur between discrete bands whose resonant frequencies are determined by each nanomagnet's mode volume and profile. Comparison with numerical simulations reveals that parametric pumping leads to scattering from bulk modes into edge modes. Furthermore, our results suggest that tunable directional scattering is possible in these structures.

[1] Lendinez et al., https://doi.org/10.21203/rs.3.rs-1636046/v1