Orbital facilitated charge transfer originated phonon mode in Cr-substituted PrFeO3: A brief Raman study

We report the possible origin of orbital facilitated new Raman mode in orthorhombic perovskite PrFe1-xCrxO3. For this purpose, resonance and power-dependent Raman spectroscopy measurements have been carried out to understand the origin of local oxygen breathing mode in the mixed Fe-Cr orthorhombic perovskites through the orbital mediated charge transfer mechanism. It has been observed that multi-phonon scattering is highly sensitive to the presence of mixed Fe-Cr ions and is absent in pure iso-structural vacuum annealed PrFeO3. The Raman spectroscopy results infer a scaling in the intensity of octahedral breathing Raman mode around 660 cm(-1), which is attributed to the lattice rearrangement due to the transfer of an electron from Cr3+(d(3)) to Fe3+(d(5)) and results to d(2)-d(6) (Cr4+-O-2-Fe2+) configuration. The interactions of d(2)-d(6) configuration are different from d(3)-d(5) configuration, which leads to the octahedral lattice rearrangement and activates the new Raman mode. The charge transfer phenomenon is supported through first-principle calculations and valence band spectroscopy.