Topological frustration of artificial spin ice

Abstract

Frustrated systems, typically characterized by competing interactions that cannot all be simultaneously satisfied, display rich behaviours not found elsewhere in nature. Artificial spin ice takes a materials-by-design approach to studying frustration, where lithographically patterned bar magnets mimic the frustrated interactions in real materials but are also amenable to direct characterization. Here, we introduce controlled topological defects into square artificial spin ice lattices in the form of lattice edge dislocations and directly observe the resulting spin configurations. We find the presence of a topological defect produces extended frustration within the system caused by a domain wall with indeterminate configuration. Away from the dislocation, the magnets are locally unfrustrated, but frustration of the lattice persists due to its topology. Our results demonstrate the non-trivial nature of topological defects in a new context, with implications for many real systems in which a typical density of dislocations could fully frustrate a canonically unfrustrated system.

Unexpected Phenomenology in Particle-Based Ice Absent in Magnetic Spin Ice

“…This does not imply, however, that violation of the ice rule, must necessarily happen in the lowest coordination vertices, as demonstrated below and as found recently [42] in square PI. This ice-rule violation through charge transfer is unique to PI, and nothing of the sort can happen in SI, where the ice rule is robust to decimation and mixed coordination [13,24,43], dislocations [44], and indeed even in clusters [41], because it is enforced by the local energy.…”

Advances in artificial spin ice

“…In thermally active artificial kagome spin ice, the emergent magnetic monopoles remain confined, because increasing the length of the strings beyond one spin flip is energetically unfavourable 34 . Therefore, important in defining the behaviour of the monopoles are the background magnetic configuration and the artificial spin-ice geometry, both of which can be modified by introducing defects into the lattice [35][36][37] . In artificial square ice, the string tension can be exploited to obtain spontaneous magnetic currents, by stretching the bound monopoles apart with an applied magnetic field and removing the field in order to release them, and it was suggested that this effect may be of interest for energy storage 38 .…”

“…Lattice defects are topological defects in the structure (Fig. 5a), and the introduction of an edge dislocation in the artificial square ice results in the creation of domain boundaries between areas of type I ground-state order that have one end pinned at the defects 37 .…”

Dynamics of reconfigurable artificial spin ice: Toward magnonic functional materials

“…In Ref. 80, physical defects such as a missing nanoisland accompanied by lattice distortion were introduced in square ice. Such defects have been found to lead to the formation of domain walls across ground state regions.…”