Lattice geometry-dependent magnon modes and harmonic generation in Permalloy antidot waveguides

Custom-engineered nanomagnonic waveguides with enhanced nonlinear properties are pivotal for advancing next-generation wave-based spintronic technologies. In this work, we systematically explore how lattice geometry influences the linear and nonlinear dynamics of Permalloy antidot waveguides. Three lattice configurations—square, rhomboid, and honeycomb—are examined. Our results reveal that introducing antidots generates localized magnon modes alongside propagating spin waves, with geometry strongly dictating localization behavior. Spin waves exhibit selective channel propagation, and in the nonlinear regime, we observe the presence of both integer and fractional harmonics. The 1.5fexc mode displays behavior similar to that of the fundamental modes, propagating through the channels, while the second harmonic reveals antisymmetric characteristics with multiple nodes across the channels. Notably, harmonic-generation efficiency in honeycomb lattices is nearly four times higher than in reference waveguides without antidots, and the second harmonic's performance depends on lattice positioning. Direct spin-wave imaging via Brillouin light microscopy confirms these findings, highlighting the promise of geometry-tailored antidot waveguides for magnon-based computing applications.