Magnetic Interaction in the Geometrically Frustrated Triangular Lattice Antiferromagnet $\rm CuFeO_2$

TL;DR

This study investigates the magnetic interactions and spin wave excitations in the frustrated triangular lattice antiferromagnet CuFeO2, revealing complex three-dimensional couplings and dynamic features linked to multiferroic behavior.

Contribution

The paper provides detailed measurements of spin wave dispersions in CuFeO2, demonstrating the necessity of multiple exchange interactions and out-of-plane coupling to understand its magnetic properties.

Findings

Multiple exchange interactions (J1, J2, J3) are essential to describe spin waves.

Out-of-plane coupling (Jz) contributes to three-dimensional magnetic behavior.

Energy dips at incommensurate wavevectors relate to multiferroic phase precursors.

Abstract

The spin wave excitations of the geometrically frustrated triangular lattice antiferromagnet (TLA) $\rm CuFeO_2$ have been measured using high resolution inelastic neutron scattering. Antiferromagnetic interactions up to third nearest neighbors in the ab plane (J_1, J_2, J_3, with $J_2/J_1 \approx 0.44$ and $J_3/J_1 \approx 0.57$), as well as out-of-plane coupling (J_z, with $J_z/J_1 \approx 0.29$) are required to describe the spin wave dispersion relations, indicating a three dimensional character of the magnetic interactions. Two energy dips in the spin wave dispersion occur at the incommensurate wavevectors associated with multiferroic phase, and can be interpreted as dynamic precursors to the magnetoelectric behavior in this system.