Abstract
We study the ground-state and low-energy properties of classical vector spin models with nearest-neighbor antiferromagnetic interactions on a class of geometrically frustrated lattices, which includes the kagome and pyrochlore lattices. We explore the behavior of these magnets that results from their large ground-state degeneracies, emphasizing universal features and systematic differences between individual models. We investigate the circumstances under which thermal fluctuations select a particular subset of the ground states, and find that this happens only for the models with the smallest ground-state degeneracies. For the pyrochlore magnets, we give an explicit construction of all ground states, and show that they are not separated by internal energy barriers. We study the precessional spin dynamics of the Heisenberg pyrochlore antiferromagnet. There is no freezing transition or selection of preferred states. Instead, the relaxation time at low temperature T is of order We argue that this behavior can also be expected in some other systems, including the Heisenberg model for the compound
- Received 16 March 1998
DOI:https://doi.org/10.1103/PhysRevB.58.12049
©1998 American Physical Society