Magnonic bending, phase shifting and interferometry in a 2D reconfigurable nanodisk crystal.

Strongly-interacting nanomagnetic systems are pivotal across next-generation technologies including reconfigurable magnonics and neuromorphic computation. Controlling magnetisation state and local coupling between neighbouring nanoelements allows vast reconfigurable functionality and a host of associated functionalities. However, existing designs typically suffer from an inability to tailor inter-element coupling post-fabrication and nanoelements restricted to a pair of Ising-like magnetisation states. Here, we propose a new class of reconfigurable magnonic crystal incorporating nanodisks as the functional element. Magnetic nanodisks are crucially bistable in macrospin and vortex states, allowing inter-element coupling to be selectively activated (macrospin) or deactivated (vortex). Through microstate engineering, we leverage the distinct coupling behaviours and magnonic band structures of bistable nanodisks to achieve reprogrammable magnonic waveguiding, bending, gating and phase-shifting across a 2D network. The potential of nanodisk-based magnonics for wave-based computation is demonstrated via an all-magnon interferometer exhibiting XNOR logic functionality. Local microstate control is achieved here via topological magnetic writing using a magnetic force microscope tip.