  We perform micromagnetic simulations to study the switching barriers in
square artificial spin ice systems consisting of elongated single domain
magnetic islands arranged on a square lattice. By considering a double vertex
composed of one central island and six nearest neighbor islands, we calculate
the energy barriers between two types of double vertices by applying the string
method. We investigate by means of micromagnetic simulations the consequences
of the neighboring islands, the inhomogeneities in the magnetization of the
islands and the reversal mechanisms on the energy barrier by comparing three
different approaches with increasing complexity. The micromagnetic models,
where the string method is applied, are compared to the currently common
method, the mean barrier approximation. Our investigations indicate that a
proper micromagnetic modeling of the switching process leads to significantly
lower energy barriers, by up to 35% compared to the mean-barrier approximation,
so decreasing the expected average life time up to seven orders of magnitude.
Hereby, we investigate the influence of parallel switching channels and the
conceptional approach of using a mean-barrier to calculate the corresponding
rates.
