Magnetoelastic Excitations In Multiferroic Hexagonal Ymno3 Studied By Inelastic X-Ray Scattering

Despite extensive studies, the exact mechanism of magnetoelastic coupling in hexagonal rare-earth manganite RMnO3 still remains under debate. Using inelastic x-ray scattering, we have measured the lattice vibrations of hexagonal manganite RMnO3 over a wide momentum-energy space to identify clear magnetoelastic excitations, which are the long-sought-after direct evidence of the dynamic magnon-phonon coupling. Our calculations using a magnetoelastic coupling model of superexchange striction quantitatively reproduces the experimental observations. Based on these results, we present a broadly applicable method to analyze the mode and momentum dependence of the magnon-phonon coupling for noncollinear magnets.