Spin phonon induced colinear order and magnetization plateaus in triangular and kagome antiferromagnets. Applications to CuFeO_2

TL;DR

This paper investigates how moderate spin-lattice couplings in triangular and Kagome antiferromagnets induce complex colinear magnetic orders and magnetization plateaus, with implications for materials like CuFeO₂.

Contribution

It demonstrates that spin-lattice coupling can generate experimentally observed and novel magnetic phases, including magnetization plateaus, in frustrated antiferromagnets.

Findings

Induces four and five sublattice states in triangular lattices.

Predicts multiple magnetization plateaus at various fractions.

Shows that strong coupling leads to striped colinear states.

Abstract

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 CuFeO$_2$. 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 $\alpha$-NaFeO$_2$ and MnBr$_2$. On the Kagome lattice, moderate spin-lattice couplings induce colinear order, but an extensive degeneracy remains.