Spin waves and magnetic interactions in LiCu2O2

TL;DR

This study investigates the spin wave excitations and magnetic interactions in LiCu2O2 using inelastic neutron scattering, revealing the limitations of simple models and providing insights into the material's complex helimagnetic behavior.

Contribution

It provides a detailed experimental analysis of spin waves in LiCu2O2 and challenges the adequacy of the simple J1-J2 model for this compound.

Findings

Measured spin wave dispersion near magnetic Bragg reflection.

Estimated exchange constants and explained geometric frustration.

Identified discrepancies with previous theoretical models.

Abstract

The quasi-one-dimensional helimagnet LiCu2O2 was studied by single crystal inelastic neutron scattering. The dispersion relation of spin wave excitations was measured in the vicinity of the principal magnetic Bragg reflection. A spin wave theoretical analysis of the data yields an estimate of the relevant exchange constants and explains the mechanism of geometric frustration that leads to helimagnetism. It is found that the simple antiferromagnetic J_1-J_2 model that was previously proposed is inadequate for LiCu2O2. The experimental findings are generally in a qualitative agreement with first principal calculations of [A. A. Gippius et al., Phys. Rev. B {\bf 70}, 020406 (2004)], though certain important discrepancies remain to be explained.