  Artificial spin ices were originally introduced as analogs of the pyrochlore
spin ices, but have since become a much richer field . The original attraction
of building nanotechnological analogs of the pyrochlores were threefold: to
allow room temperature studies of geometrical frustration; to provide model
statistical mechanical systems where all the relevant parameters in an
experiment can be tuned by design; and to be able to examine the exact
microstate of those systems using advanced magnetic microscopy methods. From
this beginning the field has grown to encompass studies of the effects of
quenched disorder, thermally activated dynamics, microwave frequency responses,
magnetotransport properties, and the development of lattice geometries--with
related emergent physics---that have no analog in naturally-occurring
crystalline systems. The field also offers the prospect of contributing to
novel magnetic logic devices, since the arrays of nanoislands that form
artificial spin ices are similar in many respects to those that are used in the
development of magnetic quantum cellular automata. In this chapter, I review
the experimental aspects of this story, complementing the theoretical chapter
by Gia-Wei Chern.
