Artificial Spin Ice: A Playground for Frustration

Artificial spin ice consists of arrays of interacting lithographically fabricated single-domain ferromagnetic elements, arranged in different geometries such that the magnetostatic interactions among the moments can be frustrated. We both design the lattice geometries and probe the individual microscopic moments, enabling us to study the accommodation of frustration with exquisite detail and flexibility. Because we conduct experiments on frustrated lattice geometries that are inaccessible in other systems, we can observe and study behavior such as strings of magnetic excitations and entropically induced long-range ordering. Artificial spin ice structures also allow studies of a range of other phenomena, including avalanche statistics, monopole-like charge excitations, and quadrupolar ordering, all of which can be probed microscopically in real space.