  Collective dynamics in lithographically-defined artificial spin ices offer
profound insights into emergent correlations and phase transitions of
geometrically-frustrated Ising spin systems. Their temporal and spatial
evolution are often simulated using kinetic Monte Carlo simulations, which rely
on the precise knowledge of the switching barriers to obtain predictive results
in agreement with experimental observations. In many cases, however, the
barriers are derived from simplified assumptions only, and do not take into
account the full physical picture of nanomagnetic switching. Here we describe
how the immediate magnetic environment of a nanomagnet reversing via
quasi-coherent rotation can induce clockwise and counter-clockwise switching
channels with different barrier energies. This barrier splitting for chiral
reversal channels can be sizeable and, as string-method micromagnetic
simulations show, is relevant for artificial spin ice systems made of both
exchange -- as well as magnetostatically --dominated units. Due to the barrier
splitting (and further reductions due to non-uniform reversal) transition rates
can be exponentially enhanced by several orders of magnitude compared to
mean-field predictions, especially in the limit of rare switching events where
thermal excitation is less likely. This leads to significantly faster
relaxation time scales and modified spatial correlations. Our findings are thus
of integral importance to achieve realistic kinetic Monte Carlo simulations of
emergent correlations in artificial spin systems, magnonic crystals, or the
evolution of nanomagnetic logic circuits.
