Laboratoire de Physique Théorique
Toulouse - UMR 5152

A hallmark of geometrical magnetic frustration is degeneracy between multiple classical spin configurations that are not related by any symmetry. Such a degeneracy can be lifted by thermal and quantum fluctuations via a so called order by disorder effect. I discuss the role of weak static disorder, nonmagnetic vacancies and random exchange bonds, on degeneracy lifting in frustrated magnets. Analytical and numerical results show that the structural disorder selects a different subset of classical ground states compared to fluctuations. Competition between quenched and thermal disorder leads to appearance of interesting and complicated phase diagrams.

I will also present the recent results on the classical Heisenberg kagome antiferromagnet with randomly modulated bonds. The spin liquid Coulomb phase appears to be remarkably stable against weak bond disorder. The transition into the spin glass state takes place only at a finite disorder strength. The random bond kagome antiferromagnet provides an interesting example of the competition between spin liquid and spin glass states and shows behavior qualitatively different from the previously studied pyrochlore antiferromagnet.