Ultrastrong magnon-magnon coupling and chiral spin-texture control in a dipolar 3D multilayered artificial spin-vortex ice

Strongly-interacting nanomagnetic arrays such as artificial spin ice (ASI) are ideal systems for exploring reconfigurable magnonics, possessing a vast range of microstates with intriguing distinct magnon dynamics. Ferromagnetic resonance has proved to be a powerful "fingerprinting" method well suited to probing ASI magnon dynamics, but accessing more than a handful of the potential range of microstates is experimentally challenging [1-3]. By designing ASI with a range of switching fields via differential fabrication (subsets of nanomagents with different widths) and tuning island dimensions to support bistable macrospin and vortex states, we can increase both the range of accessible states and magnon dynamics for functional processing including Neuromorphic Computing [4]. Beyond this, we have recently shown that expanding ASI into three-dimensional architectures can further enhance the breadth of ASI microstates and depth of emergent magnon dynamics [5]. The energetic landscape of ASI is modified in this configuration as a function of the distance between the layers [6]. By fabricating multi-layered ASI arrays comprising two magnetic layers & a non-magnetic spacer, we demonstrate a range of phenomena including ultrastrong dipolar magnon-magnon coupling and magnon frequency combing. [5].