Brillouin light scattering spectral fingerprinting of magnetic microstates in artificial spin ice

The family of nanomagnetic arrays termed artificial spin ice (ASI) possess a vast range of metastable microstates. These states exhibit both exotic fundamental physics and more recently applied functionality, garnering attention as reconfigurable magnonic circuits and neuromorphic computing platforms. However, open questions remain on the role of microstate imperfections or angular disorder – particularly in the GHz response of the system. We report a study on the GHz dynamics of a series of five carefully prepared microstates in the same ASI sample, with both coexistence of vortex and uniformly magnetized macrospins, and disorder in the orientation of the macrospins at different vertices. We observe microstate-specific mode frequency shifting, mode creation and mode crossing. This versatility of characteristic spin-wave (SW) peaks for specific magnetic microstates in ASI enables identification of microstate configurations via SW spectral characterization. The wide reconfigurability of microstate-specific SW dynamics also opens avenues for developing rich magnonic devices operating in the GHz frequency regime and advances the understanding of ASI physics.