We report a field-driven reconfiguration of accessible magnetization-state sets in square Permalloy nanoelements under a common erase protocol. Rather than showing a monotonic increase in the number of reachable remanent states with increasing write-field amplitude, the system exhibits two sharp reconfiguration thresholds. Following +x erase, the accessible state set changes from E, N, NE, S, SE at 18-21 mT to E, NE, NW, SE, SW at 22-27 mT, and then expands to E, N, NE, NW, S, SE, SW at 28-30 mT. Reversing the erase polarity yields the exact mirror sequence. Additional simulations confirm numerical robustness against mesh variation, systematic threshold shifts with thickness and corner rounding, degradation under edge roughness above about 2-3 nm, partial thermal retention at 300 K, and size-dependent evolution up to the micrometer scale. These results establish accessible-state-set reconfiguration as a distinct micromagnetic phenomenon and support its interpretation as a history-dependent field-window response in square Permalloy nanoelements.
Yohna Kim (Fri,) studied this question.