Observation and control of collective spin-wave mode hybridization in chevron arrays and in square, staircase, and brickwork artificial spin ices
Troy Dion, Jack C. Gartside, Alex Vanstone, Kilian D. Stenning, Daan M. Arroo, H. Kurebayashi, W. R. Branford
Abstract
Dipolar magnon-magnon coupling has long been predicted in nanopatterned artificial spin systems. However, observation of such phenomena and related collective spin-wave signatures have until recently proved elusive or been limited to low-power edge modes which are difficult to measure experimentally. Here we describe the requisite conditions for dipolar mode-hybridization, how it may be controlled, why it was not observed earlier, and how strong coupling may occur between nanomagnet bulk modes. We experimentally investigate four nanopatterned artificial spin system geometries: chevron arrays, square, staircase, and brickwork artificial spin ices. We observe significant dynamic dipolar-coupling in all systems with relative coupling strengths and avoided-crossing gaps supported by micromagnetic-simulation results. We demonstrate reconfigurable mode-hybridization regimes in each system via microstate control, and in doing so elucidate the underlying dynamics governing dynamic dipolar-coupling with implications across reconfigurable magnonics. We demonstrate that confinement of the bulk modes via edge effects plays a critical role in dipolar hybridized modes, and treating each nanoisland as a coherently precessing macro-spin or a standing spin-wave is insufficient to capture experimentally observed coupling phenomena. Finally, we present a parameter-space search detailing how coupling strength may be tuned via nanofabrication dimensions and material properties.