Magnetic monopoles in spin ice

Real-space observation of emergent magnetic monopoles and associated Dirac strings in artificial kagome spin ice.
Elena Mengotti, Laura J. Heyderman , Arantxa Fraile Rodríguez , Frithjof Nolting , Remo V. Hügli , Hans-Benjamin Braun
Nature Physics 7, 68 (2011)

a, Schematic view of the nanolithographic array of permalloy islands with anisotropy axes along honeycomb links and the orientation of the magnetization indicated by arrows. . b, Corresponding charge distribution with magnetic moments replaced by dumbbells carrying charge q and −q (in red and blue).