  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.
