Inelastic x-ray scattering with meV energy resolution (IXS) is an ideal tool to measure collective excitations in solids and liquids. In non-resonant scattering condition, the cross section is strongly dominated by lattice vibrations (phonons). However, it is possible to probe additional degrees of freedom such as magnetic fluctuations that are strongly coupled to the phonons. The IXS spectrum of the coupled system will contain not only the phonon dispersion (majority component) but also the so far undetected magnetic correlation function (minority component). Here we report the discovery of strong magnon-phonon coupling in LiCrO2 that enables the measurement of magnetic correlations throughout the Brillouin-zone via IXS. We found electromagnon excitations and electric dipole active two-magnon excitations in the magnetically ordered phase and paraelectromagnons in the paramagnetic phase of LiCrO2. We predict that the numerous group of (frustrated) magnets with dominant direct exchange and non-collinear magnetism shows similarly strong coupling and surprisingly large and measurable IXS cross section for magnons and multi-magnon processes.
@article{arxiv.1606.07321,
title = {Electromagnon dispersion probed by inelastic x-ray scattering},
author = {Sándor Tóth and Björn Wehinger and Katharina Rolfs and Turan Birol and Uwe Stuhr and Hiroshi Takatsu and Kenta Kimura and Tsuyoshi Kimura and Henrik M. Rønnow and Christian Rüegg},
journal= {arXiv preprint arXiv:1606.07321},
year = {2016}
}