Tuning vertex configurations in connected artificial spin ice through geometry, field direction, and defect engineering

Artificial spin ice (ASI) provides a versatile platform to study magnetic frustration and emergent vertex states, whose populations govern the system’s behavior. In this work, we focus on connected kagome ASI, where nanoislands are physically and electrically linked at the vertices, enabling exchange coupling at nanobar junctions in addition to dipolar interactions. Using micromagnetic simulations, we identify three mechanisms to control vertex populations. First, varying the nanobar aspect ratio modifies the balance of shape anisotropy and interaction energies. Second, changing the orientation of the applied magnetic field alters magnetization reversal pathways, resulting in systematic variation of vertex populations across the hysteresis loop. Third, introducing controlled lattice defects through selective island removal locally perturbs the interaction landscape, enabling spatially selective stabilization or suppression of vertex states. We further show that elevated populations of certain vertex types arise predominantly as transient, non-equilibrium configurations during field-driven evolution. Time-dependent simulations reveal that these states relax on short timescales toward distributions consistent with experimentally observed vertex populations. These results demonstrate that vertex populations and switching behavior in connected kagome ASI can be tuned through geometry, field orientation, and engineered defects, providing a framework for controlled design of magnetic states in frustrated nanomagnetic systems, with an emphasis on their dynamical accessibility.