Artificial spin ice consists of arrays of lithographically fabricated single-domain ferromagnetic elements, arranged in different geometries such that the magnetostatic interactions between the moments are frustrated.  Because we can both design the lattice geometries and probe the individual moments, these systems allow us to study the accommodation of frustration with exquisite detail and flexibility.  

I will report results from a number of recent experimental efforts in artificial spin ice in our group. The first area of research consists of studies of artificial spin ice arrays with lattice geometries that are unavailable in natural systems and are specifically designed to manifest novel forms of frustration. These so-called “vertex frustrated” lattices demonstrate that novel forms of frustration result in unusual collective behavior. The second area of research is detailed electrical transport studies of connected artificial spin ice systems. We find that appropriate micromagnetic modeling allows us to explain the fascinating collective magnetoresistance phenomena in these systems and reveals the crucial role of the vertex regions in how electronic transport is manifested.   I will conclude with a discussion of additional recent work, including noise associated with a plasma of monopole-like elementary excitations.

References: Schiffer and Nisoli, Appl. Phys. Lett. 118, 110501 (2021); Goryca et al., Phys. Rev. X 11, 011042 (2021); Zhang et al. Nature Comm 12, 6514 (2021); Saglam et al., Nature Physics 18, 706 (2022); Bingham et al., Phys. Rev. Lett. 127, 207203 (2021) and Phys. Rev. Lett. 129, 067201 (2022).