Magnetic monopoles have recently been discovered in so-called spin-ice materials. The measurement of magnetic current in a spin-ice crystal now demonstrates the macroscopic consequences of these free, magnetically charged particles, and establishes a perfect equivalence between the bulk electrical properties of a conducting fluid and the bulk magnetic properties of spin ice in the magnetic-monopole regime.
- S. R. Giblin
- S. T. Bramwell
- I. Terry