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Description
Artificial spin ice (ASI) exhibits an effect referred to as return point memory (RPM) [1, 2] where the system cycles through exactly the same microstates upon subsequence field loops. The pathway the system takes as a result of the field protocol is strongly constrained by the quenched disorder of the system and the initial microstate the system starts in. While previous studies have focused on the effects of the quenched disorder on RPM little has been done on the effects of the initial microstate.
How the initial microstate influences the RPM behaviour is studied using a dipolar needle simulation and magnetic force microscopy. The simulation models the bars in response to applied magnetic field protocols including the local dipole field. The quenched disorder of the fabricated lattice is replicated in the simulation to identify critical macrospins that lead to different RPM states. The nanomagnetic writing technique allows access to specific microstates to experimentally test the RPM behaviour from various initial microstates.
[1] Libál, A. et al. (2012). Hysteresis and return-point memory in colloidal artificial spin ice systems. Physical Review E, 86(2), 1–5.
[2] Gilbert, I. et al. (2015). Direct visualization of memory effects in artificial spin ice. Physical Review B, 92(10), 104417.
