Pressure-induced phase transition and phonon softening in h-Lu_0.6Sc_0.4FeO₃

We combine diamond anvil cell techniques, synchrotron-based infrared and Raman scattering spectroscopies, a symmetry analysis, and complementary lattice dynamics calculations to explore the pressure-driven phase transition in multiferroic h-Lu0.6Sc0.4FeO3. Comparison of the measured and predicted phonon patterns reveals a P6(3)cm -> P (3) over bar c1 structural transition at 15 GPa. Symmetry breaking across the polar -> antipolar transition takes place via changes in the bipyramidal tilting direction and Lu/Sc displacement pattern, analogous to the strain-driven K-3 distortion pathway in h-LuFeO3 and temperature-induced transitions in the rare-earth manganites.