Critical phenomena in a highly constrained classical spin system: Neel ordering from the Coulomb phase

Pickles, T. S.; Saunders, T. E.; Chalker, J. T.

Critical phenomena in a highly constrained classical spin system: Neel ordering from the Coulomb phase

Authors

Pickles, T. S.

Saunders, T. E.

Chalker, J. T.

Description

Many classical, geometrically frustrated antiferromagnets have macroscopically degenerate ground states. In a class of three-dimensional systems, the set of degenerate ground states has power-law correlations and is an example of a Coulomb phase. We investigate Neel ordering from such a Coulomb phase, induced by weak additional interactions that lift the degeneracy. We show that the critical point belongs to a universality class that is different from the one for the equivalent transition out of the paramagnetic phase, and that it is characterised by effective long-range interactions; alternatively, ordering may be discontinuous. We suggest that a transition of this type may be realised by applying uniaxial stress to a pyrochlore antiferromagnet.
4 pages, 3 figures