Electromagnon dispersion probed by inelastic X-ray scattering in LiCrO₂

Lattice vibrations (phonons) in crystals are typically weakly interacting with the electronic and magnetic degrees of freedom, such as charge and spin fluctuations. Researchers of PSI together with collaborators from EPF Lausanne, Japan and USA discovered an unexpectedly strong coupling between lattice vibrations and spin fluctuations in the quantum magnet LiCrO₂. The observed magnetoelastic waves or electromagnons carry both electric and magnetic dipole moment. This was proven using complementary studies with non-resonant inelastic X-ray scattering at ESRF and on the EIGER thermal neutron triple-axis-spectrometer at SINQ, PSI. The experimental data together with model calculations revealed the underlying coupling mechanism. These results will help to develop better multiferroic materials and demonstrate that inelastic X-ray scattering can probe magnetism with high energy resolution in special systems in strong spin-lattice coupling.