Magnetic monopole density and antiferromagnetic domain control in spin-ice iridates

Magnetically frustrated systems provide fertile ground for complex behaviour, including unconventional ground states with emergent symmetries, topological properties, and exotic excitations. A canonical example is the emergence of magnetic-charge-carrying quasiparticles in spin-ice compounds. Despite extensive work, a reliable experimental indicator of the density of these magnetic monopoles is yet to be found. Using measurements on single crystals of Ho2Ir2O7 combined with dipolar Monte Carlo simulations, we show that the isothermal magnetoresistance is highly sensitive to the monopole density. Moreover, we uncover an unexpected and strong coupling between the monopoles on the holmium sublattice and the antiferromagnetically ordered iridium ions. These results pave the way towards a quantitative experimental measure of monopole density and demonstrate the ability to control antiferromagnetic domain walls using a uniform external magnetic field, a key goal in the design of next-generation spintronic devices. Magnetic monopoles emerge as magnetic excitations in spin ices, but their direct detection has been challenging. Here the authors show that the magnetoresistance in a pyrochlore iridate spin ice could be used as a measure of the monopole density and demonstrate magnetic-field control of the antiferromagnetic iridium domain walls.

Automated summary

Magnetically frustrated systems exhibit complex behavior such as emergent symmetries, topological properties, and exotic excitations, with the reliable experimental indicator of the density of magnetic monopoles remaining elusive despite extensive research. This study demonstrates a strong coupling between monopoles on the holmium sublattice and antiferromagnetically ordered iridium ions, paving the way for a quantitative experimental measure of monopole density. Furthermore, the research showcases the ability to control antiferromagnetic domain walls using a uniform external magnetic field, a crucial step towards enhancing future spintronic device design.