Imaging the stochastic microstructure and dynamic development of correlations in perpendicular artificial spin ice

Abstract

We use spatially resolved magneto-optical Kerr microscopy to track the complete microstates of arrays of perpendicular anisotropy nanomagnets during magnetization hysteresis cycles. These measurements, along with our statistical methodology, allow us to disentangle the intertwined effects of nearest-neighbor interactions, disorder, and stochasticity on magnetization switching. We find that the nearest-neighbor correlations depend on both interaction strength and disorder. We also find that although the global characteristics of the hysteretic switching are repeatable, the exact microstate sampled is stochastic with the behavior of individual islands varying between nominally identical runs. These protocols provide another way of understanding the relationship between macrohistory and microhistory in artificial magnetic arrays.