Tuning the Magnetostructural Phases of Pr₂O₃ with Pressure and Magnetic Field

The energetic proximity of crystal electric field (CEF) and phonon excitations in rare-earth materials can produce many realizations of strong electron-phonon coupling. We present temperature-, pressure-, and magnetic field-dependent Raman scattering measurements of Pr₂O₃, which reveal phonon anomalies, CEF excitations, and evidence for strong phonon-CEF coupling. We show that both an applied magnetic field and pressure induce a similar splitting of the doubly degenerate first excited CEF level, suggesting that pressure and magnetic field have the similar effect of splitting the doubly degenerate CEF excited state into singlet states having opposite angular momenta. We suggest that Pr₂O₃ shows promise for observing pressure-induced magnetic order at sufficiently high pressures.