Tunable power-phase distributions in a phonon-magnon-coupled magnon microwave antenna for reservoir computing

Exploring the power and phase profiles of spin waves not only enhances our fundamental understanding of magnetic materials but also opens up avenues for energy-efficient technologies such as spintronics, magnonics, and potentially reservoir computing. Here, we present the power-phase distributions and their tunability of a surface-acoustic-wave-driven ``magnon microwave antenna'' (MMA), comprising patterned arrays of magnetostrictive nanomagnets embedded in piezoelectric heterostructures. The MMA generates tunable microwave frequencies without external bias fields, thanks to phonon-magnon coupling, producing multimode microwave frequencies with nonvolatile spin textures. A comprehensive static magnetic study elucidates the crucial role of the demagnetization energy distribution, rather than its overall magnitude in magnetization reversal processes. Additionally, functional tunability could be achieved through amplitude-dependent training using various combinations of nanowire and nanodot dimensions, topologies, material properties, and array configurations. The nonvolatile nature of the spin textures generated in the MMA under bias-field-free conditions is promising for energy-efficient logic and low-power computing applications. Thus this work introduces a novel alternative approach, paving the way to utilize these MMAs for on-chip reservoir computing, where amplitude varies at the operating frequency.