Lattice-coupled Antiferromagnet on Frustrated Lattices

TL;DR

This paper investigates how spin-lattice interactions influence magnetic ordering and lattice deformations in frustrated antiferromagnetic systems on triangular, Kagome, and pyrochlore lattices, revealing distinct behaviors and supporting experimental observations.

Contribution

It provides a detailed analysis of spin-lattice coupling effects in various frustrated lattices, highlighting the unique case of pyrochlore structures and proposing a model consistent with recent experiments.

Findings

No static lattice deformation in triangular and Kagome lattices.

Spin-lattice coupling induces hexagon contraction in pyrochlore lattices.

Residual interactions form a 3-state Potts model with orthogonal spin directions.

Abstract

Lattice-coupled antiferromagnetic spin model is analyzed for a number of frustrated lattices: triangular, Kagome, and pyrochlore. In triangular and Kagome lattices where ground state spins are locally ordered, the spin-lattice interaction does not lead to a static deformation of the lattice. In the pyrochlore structure, spin-lattice coupling supports a picture of the hexagon spin cluster proposed in the recent experiment[S. H. Lee et al. Nature, 418, 856 (2002)]. Through spin-lattice interaction a uniform contraction of the individual hexagons in the pyrochlore lattice can take place and reduce the exchange energy. Residual hexagon-hexagon interaction takes the form of a 3-states Potts model where the preferred directions of the spin-loop directors for nearby hexagons are mutually orthogonal.