Selected magnetoelectrical phonon stiffening in Cr 2 O 3

Using inelastic neutron scattering and first-principles calculations, the authors investigate here the origin of anomalous phonon stiffening in Cr₂O₃. They challenge the common belief that dynamic spin-phonon interactions are responsible for this behavior. The findings attribute the stiffening to a static effect---the renormalization of electron states owing to the magnetic transition. This work suggests that the proposed static origin may dominate phonon energy shifts, prompting a reevaluation of phonon stiffening in other magnetic materials.