Zero-energy excitation in the classical kagome antiferromagnet NaBa$_{2}$Mn$_{3}$F$_{11}$

TL;DR

This study uses inelastic neutron scattering to identify a zero-energy excitation in the classical kagome antiferromagnet NaBa₂Mn₃F₁₁, revealing a dispersionless mode influenced by dipole interactions.

Contribution

It provides experimental evidence of a zero-energy mode in NaBa₂Mn₃F₁₁ and links it to dipole interactions, advancing understanding of kagome antiferromagnets.

Findings

Identification of a zero-energy excitation with strong low-energy intensity.

Observation of dispersive high-energy excitations.

Confirmation that dipole interactions lift the zero-energy mode.

Abstract

We performed inelastic neutron scattering measurements on a polycrystalline sample of a classical kagome antiferromagnet NaBa$_{2}$Mn$_{3}$F$_{11}$ to investigate the possibility of a dispersionless zero-energy excitation associated with rotation of spins along the chains. The observed spectra indeed exhibit such an excitation with strong intensity at low energy, as well as dispersive excitations with weak intensity at high energy. Combining the measurements with calculations from linear spin-wave theory reveals that NaBa$_{2}$Mn$_{3}$F$_{11}$ is a good realization of the classical kagome antiferromagnet which exhibits a dispersionless mode lifted by the magnetic dipole-dipole interaction.