Background: A bar magnet has two poles, denoted as +1
and -1 magnetic charges. Patterned
structures consist of many magnets (Fig. 1), where the square array (Fig. 1a)
does not, whereas the honeycomb (Fig. 1b) has, net magnetic charges (or magnetic
monopoles). Under a magnetic field these
local magnetic monopoles will move (Fig. 1c).
This latter structure is called “spin ice”, because it has a large
number of nearly degenerate configurations.
This work: We propose a theoretical model of the
dynamics in artificial spin ice under an applied magnetic field, where
magnetization reversal (Fig. 2) is mediated by domain walls carrying two units
of magnetic charges, in agreement with experiment.