Nature Phys. doi:10.1038/nphys1227 (2009)

Might it be possible to have a north magnetic pole without a corresponding south? Despite three-quarters of a century of theoretical investigation and occasional searches, such unpaired poles or 'monopoles' have yet to be seen.

There is growing evidence that 'spin ices', materials containing rare-Earth ions locked into pyramidal lattices, could create something akin to monopoles as a result of the collective behaviour of their individual atoms. Ludovic Jaubert and Peter Holdsworth of the University of Lyon in France have added to that evidence. They show that experimental data for the dynamic magnetic properties of a spin ice are well interpreted in terms of the behaviour of monopoles.