Abstract
The authors use Raman spectroscopy to study anomalous phonon-softening with decreasing temperature and the pressure- and magnetic field-dependent crystal electric field splittings in hexagonal Pr${}_{2}$O${}_{3}$.
Highlights
The energetic proximity of phononic states to the atomiclike f -electronic crystal-electric-field (CEF) levels in rare earth materials is conducive to strong electron-phonon coupling that can give rise to interesting phenomena and novel material properties
We present a temperature, pressure, and magnetic field-dependent Raman scattering study of Pr2O3 that reveals soft phonon mode behavior and anomalies associated with crystal electric field (CEF) excitations, which are indicative of strong phonon-CEF coupling
In addition to the phonon modes, at low temperatures, we observe excitations at 124 and 527 cm−1 (Fig. 1, red/lower spectrum) which we identify as crystal electric field (CEF) excitations associated with transitions among the electronic levels of the Pr3+ 3H4 manifold
Summary
The energetic proximity of phononic states to the atomiclike f -electronic crystal-electric-field (CEF) levels in rare earth materials is conducive to strong electron-phonon coupling that can give rise to interesting phenomena and novel material properties. Recent Raman scattering measurements revealed that the onset of a giant magnetodielectric response and Néel ordering in Ce2O3 is associated with emergent vibronic modes, i.e., coupled phonon and crystal electric field excitations [8]. These results suggest a novel mechanism for magnetoresponsive behavior—namely, a field-tunable coupling between electronic and phononic degrees of freedom—that may be prevalent in rare-earth materials.
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