Raman Study of Crystal Field Excitations and Soft Modes in Pr2O3

The rare earth sesquioxides constitute an interesting class of materials because of the diverse ways in which lattice degrees of freedom interact with f-electrons. Several members of this class of materials exhibit unit cell doubling, as is the case with La2O3 at high pressures, or magnetodielectric effects, such as Ce2O3 at low temperatures, however Pr2O3 has only been only minimally investigated under high pressures or high fields. We report a preliminary Raman scattering study of the phonon and crystal field excitations Pr2O3 as functions of temperature and magnetic field. We observe significant softening of an A1g phonon that may be indicative of an incipient structural distortion that cannot be accessed at ambient pressures. Two crystal field excitations (CFEs) are also observed at low temperatures, and we observe splitting and evidence of electron-phonon coupling effects associated with the lowest CFE under an applied magnetic field.. We discuss the relevance of these results to the possibility of a pressure-dependent structural change for Pr2O3.