Temperature‐dependent Raman study of PrFeO₃thin film

Abstract

Low-temperature Raman study of (001)-oriented PrFeO 3 thin film of around 200 nm thickness deposited on a LaAlO 3 (001) substrate by using the pulsed-laser deposition technique is presented. X-ray diffraction analysis of this film shows an orthorhombic structure with Pbnm space group. The observed substrate-induced strain is found to be small. In the room temperature Raman spectra, different Raman modes were observed that were classified according to the orthorhombic structure. All the observed modes show a decrease in wavenumber with rise in temperature, except the B 1g mode (624 cm −1 ) which shows some anomalous behavior. We tried to correlate the variations in linewidth and position with temperature for the observed modes with the octahedral disorder of FeO 6 . Many possibilities are presented to explain the observed results.

Cluster Glass Behavior in Orthorhombic SmFeO3 Perovskite: Interplay between Spin Ordering and Lattice Dynamics

“…There are 24 Raman active modes for the materials with the Pbnm space group, and they are 7 A g , 5 B 1g , 7 B 2g , and 5 B 3g . , Figure shows the temperature-dependent Raman spectra of the SmFeO 3 sample in the spectral range of 100–700 cm –1 from temperature 90 to 300 K. The mode assignments have been done according to the suggestion made by Weber et al The vibration modes A g (1) , A g (2) , and B 2g (2) at around 109, 142, and 157 cm –1 , respectively, are identified as a result of Sm–O bond stretching . The B 1g (2) , B 2g (3) , A g (4) , A g (5) , B 1g (4) , B 3g (3) , B 2g (5) , and A g (7) vibration modes that arise in the spectral range of 200–500 cm –1 are found to be mainly dominated by FeO 6 octahedron bending, squeezing, and scissoring-like bending. − The vibration mode around 624 cm –1 is attributed to the asymmetric stretching of the Fe–O bond, which is identified as B 2g (7) , although the behavior of this mode is similar to the A g mode …”

Crystal Structure and Concentration-Driven Phase Transitions in Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) Prepared by the Sol–Gel Method

“…The positions of the fundamental bands were very similar to those in the Raman spectrum of a single-crystal LuFeO 3 sample [ 40 ], thus indicating a high phase purity of the studied compound. Based on the frequency value, the vibrational bands below ~200 cm −1 could be considered associated mainly with vibrations of heavy rare-earth ions, the vibrational modes ranging from 200 to 350 cm −1 could be related to tilting motions of FeO 6 octahedra, the bands in the frequency region from 350 to 500 cm −1 belonged mainly to the oxygen bending modes, and the vibrational modes at wavenumbers higher than 500 cm −1 were related to symmetric stretching vibrations of Fe–O bonds [ 41 , 42 ].…”

“…This band had two components located near 523 and 546 cm −1 ; the higher-frequency blue-shifted component clearly appeared for the compound with x = 0.75. Because the vibrational modes in the frequency region above 500 cm −1 are related mainly to Fe–O stretching vibrations [ 41 , 42 ], this may indicate a strengthening of the corresponding bond. It should be noted that the spectral parameters of the strong band near 112 cm −1 remained essentially unchanged, which suggested that the local structure in the vicinity of heavy Lu ions remained similar.…”

Effects of mechanochemical activation on the structural and electrical properties of orthorhombic LuFeO3 ceramics

“…Schematically, the low wavenumber modes below 200 cm −1 are controlled by displacements namely stretching modes of heavy rare‐earth ions; those mid wavenumber ranging from 200 to 350 cm −1 are largely related to FeO 6 octahedral tilting motions, whereas 350–500 cm −1 modes are ascribed to displacements namely oxygen bending motions. High wavenumbers (>500 cm −1 ) corresponds to symmetric Fe–O stretching motions 31 . The room temperature micro‐Raman spectra of the CSS and MAS samples are represented in Figure 5.…”