Thermoremanent magnetic nanoparticles (MNPs) can self-assemble into rings through dipolar interactions, when dispersed under appropriate conditions. Analysis of individual MNP rings and clusters by off-axis electron holography reveals bistable flux closure (FC) states at ambient temperatures, and their reversible switching by magnetic field gradients. We introduce a line-bond formalism to describe the coupling between MNPs.
Wei, A., Kasama, T., & Dunin-Borkowski, R. E. (2011). Self-assembly and flux closure studies of magnetic nanoparticle rings. Journal of Materials Chemistry, 21(42), 16686-16693. https://doi.org/10.1039/c1jm11916h