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

Abstract

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+(d3) to Fe3+(d5) and results to d2–d6 (Cr4+–O−2–Fe2+) configuration. The interactions of d2–d6 configuration are different from d3–d5 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.

Effect of Dopant Concentrations on the Luminescent Properties of LiAl5O8:Fe Phosphors

“…4 A 2 emission presents a much more noticeable shape and intensity, which is due to the excitation energy used (7112 eV) having an approximate value similar to the excitation energy of the Cr K-edge (5979 eV), another possibility is that there is a process of energy transfer between Fe 3þ and Cr 3þ ions. [34,35] The variation of XEOL intensity with Fe concentration has a behavior similar to the PL spectrum (see Figure 4 and 5) with a maximum intensity for 1 mol% Fe 3þ samples.…”

Investigations on the Electronic Structure of the Strongly Correlated Electron System Cr-Doped PrFeO3

“…In the present investigations, the estimated values of the Goldschmidt structural tolerance factor scale with Cr content (see Figure 1), indicating the increase in the stability and tendency toward the cubic structure (Fe−O−Fe = 180°), and as a result of the same, the Fe−O−Fe bond angle also increases systematically. 34 3.2. X-ray Absorption Spectroscopy at Fe L-Edge, Cr L-Edge, and Oxygen K-Edge.…”

“…Moreover, the emergence of electron−phonon coupling in Jahn−Teller compounds such as manganites is well known. 34 However, the existence of the said electron-lattice coupling in JT inactive compounds and its mechanism is not explored so far in detail and would turn into very interesting information. In addition to this, the antiferromagnetic ordering temperature for PrFeO 3 (730 K) can be adjusted near to RT with the incorporation of Cr doping, scaling the possibility of magnetoelectric coupling and possibility of fabricating RT-based novel multiferroic devices.…”

Strong Impact of Cr Doping on Structural and Magnetic Properties of Bi0.5La0.5Fe1−xCrxO3−δ

“…45 It is important to note that the AS and SS modes are not allowed for orthorhombic non-Jahn-Teller (JT)-active systems. [50][51][52] The presence of these modes in Bi 0.5 La 0.5 FeO 3 could be activated by oxygen vacancies, disorder/local lattice imperfection, etc. [50][51][52] Comparing the energies of the two second-order scattering and first-order vibrational modes, it can be proposed that the lines observed at 965 cm À1 and 1092 cm À1 correspond to two-phonon 2B 2g (2) and 2AS modes, respectively.…”

“…45,51,53 The line observed at 500 cm À1 can be attributed to Cr-induced structural disorder (SD), whereas the line seen at around 660 cm À1 can be assigned to the breathing (BR) mode of FeO 6 octahedra activated by orbital-mediated charge transfer between Fe 3+ and Cr 3+ ions. 11,45,[51][52][53][54][55] The lines observed at around 1235 and 1333 cm À1 are second-order modes of the SS and BR modes, respectively. Upon increase of the Cr concentration, the SS and BR modes as well as their second-order counterparts shifted towards higher wavenumber, consistent with the decrease in the M-O bond length with increasing Cr content shown by the NPD results.…”