Magnetic charge crystals imaged in artificial spin ice

Magnetic charge crystals imaged in artificial spin ice
A team of scientists has reported direct visualization of magnetic charge crystallization in an artificial spin ice material, a first in the study of a relatively new class of frustrated artificial magnetic materials-by-design known as "Artificial Spin Ice." These charges are analogs to electrical charges with possible applications in magnetic memories and devices.

The unique properties of spin ice materials have fascinated scientists since they were first discovered in the late 1990s in naturally occurring rare earth titanites. The material is aptly named: the highly complex ordering of nanoscale magnets in spin ice obey the same rules that determine the positional ordering of hydrogen and oxygen atoms in frozen water ice. Both have "spin", degrees of freedom—with frustrated interactions that prevent complete freezing, even at absolute zero.

The image bellow shows the topography of a sample of artificial kagome spin ice. The ends of the islands have been shaded blue and orange according to the magnetic polarity, and the plus and minus signs denote the net magnetic charge at each three-island vertex. Thermal annealing forms crystallites of magnetic charges of alternating sign.

Source and further reading:
http://phys.org/news/2013-08-magnetic-crystals-imaged-artificial-ice.html
Image credit: Alex David Jerez Roman, Ian Gilbert, and Sheng Zhang