Magnon-phonon coupling and two-magnon continuum in two-dimensional triangular antiferromagnet CuCrO2

TL;DR

This study investigates magnon-phonon interactions and continuum excitations in the 2D triangular antiferromagnet CuCrO2 using inelastic neutron scattering, revealing coupling effects and complex magnetic excitations.

Contribution

The paper provides direct experimental evidence of magnon-phonon coupling in CuCrO2 and introduces a model Hamiltonian that accurately reproduces observed excitation features.

Findings

Evidence of magnon-phonon coupling at 12.5 meV

Observation of continuum excitations at the zone boundary

Model Hamiltonian reproduces experimental features

Abstract

CuCrO2 is a manifestation of a two-dimensional triangular antiferromagnet which exhibits an incommensurate noncollinear magnetic structure similar to a classical 120 degree ordering. Using the inelastic neutron scattering technique, direct evidence of a magnon-phonon coupling in CuCrO2 is revealed via the mixed magnon-phonon character of the excitation mode at 12.5 meV as well as a minimum at the zone boundary. A simple model Hamiltonian that incorporates an exchange striction type magnon-phonon coupling reproduces the observed features accurately. Also, continuum excitations originating from the interaction between quasiparticles are observed with strong intensity at the zone boundary. These features of the magnetic excitations are key to an understanding of the emergent excitations in noncollinear antiferromagnetic compounds.