Coupling between spin and lattice degrees of freedom are important in geometrically frustrated magnets where they can lead to degeneracy lifting and novel orders. We show that moderate spin-lattice couplings in triangular and Kagome antiferromagnets can induce complex colinear magnetic orders. When classical Heisenberg spins on the triangular lattice are coupled to Einstein phonons, a rich variety of phases emerge, including the experimentally observed four sublattice state and the five sublattice 1/5th plateau state seen in the magneto-electric material CuFeO2. In addition we predict magnetization plateaus at 1/3, 3/7, 1/2, 3/5 and 5/7 at these couplings. Strong spin-lattice couplings induce a striped colinear state, seen in α-NaFeO2 and MnBr2. On the Kagome lattice, moderate spin-lattice couplings induce colinear order, but an extensive degeneracy remains.
@article{arxiv.0709.3546,
title = {Spin phonon induced colinear order and magnetization plateaus in triangular and kagome antiferromagnets. Applications to CuFeO_2},
author = {Fa Wang and Ashvin Vishwanath},
journal= {arXiv preprint arXiv:0709.3546},
year = {2008}
}