Magnetic-field dependent phonon states in paramagnetic CeF3

Raman scattering experiments in paramagnetic uniaxial CeF₃ at helium temperature demonstrate a splitting of some degenerate (E_g)-phonon states in an external magnetic field parallel to the crystal axis. A linear splitting is observed in low fields, followed by a field independent (saturation) splitting in high fields. In addition, changes in the Raman scattering efficiencies and a reduction of the line width of phonon transitions are observed with increasing magnetic fields. No such effects are observed for magnetic fields perpendicular to the crystal axis. The splittings of degenerate phonon modes are related to the paramagnetic saturation 〈S_z〉.