Symmetry breaking in Ni-doped PrFeO₃ thin films established by Raman study

Abstract

Structural and Raman study of PrFe 1Àx Ni x O 3 (0 x 0.5) thin films deposited on LaAlO 3 substrate by Pulse laser deposition is presented. Structural analysis by X-ray diffraction shows that these films are highly epitaxial grown along the c-axis with (0 0 l) orientation and have an orthorhombic structure with space group Pbnm throughout the doping range. From Raman spectrum, a new peak starts developing at around 574 cm À1 in this system with Ni doping. However, after x ¼ 0.3 Ni concentration, there is a decline in intensity of this observed peak and for x ! 0.3, it (this mode) becomes hard to resolve with other observed modes. The generation of this new peak (574 cm À1 ) in the other similar system (LaFe 1Àx Ni x O 3 ) with Ni doping is also observed. This study is a direct indication of a structural phase transition (SPT) or symmetry breaking in the present and related systems. The established orthorhombic structure for the present and related system is doubtful.

Strain induced disordered phonon modes in Cr doped PrFeO3

“…Hence, it appears that the formation of new Raman mode in the Raman spectra is possibly due to structural disorder [40,54,55]. Present results are in well agreement with earlier reports [54,[60][61][62]. In order to further confirm the appearance of Raman mode around 510 cm −1 is due to the structural disorder; laser irradiation has been carried out on pure PrFeO It is important here to note that various researchers have used laser and irradiation to produce the structural disorder [40,54,55,63].…”

“…As discussed in earlier section, the generation of new mode in Raman spectra with Cr doping can be due to structural disorder [54,55] or due to symmetry breaking [56,60], SXRD studies do not show any new peak due to symmetry breaking as no new peak in the diffraction patter appears or existing peak disappears even at much higher values of 2θ where the resolution of the system is much higher. Hence, it appears that the formation of new Raman mode in the Raman spectra is possibly due to structural disorder [40,54,55].…”

“…It is important here to note that both PrFeO 3 and PrCrO 3 have orthorhombic structure and have 24 Raman active modes [23,53]; hence, from Raman spectrum it's not easily possible to differentiate the orthorhombic and any other space group. However, any change in the spectrum with incorporation of doping is expected to be either due to a structural phase transition or it can also be treated as disordered phonon modes [54][55][56]60]. It is clear from the figure 3(a) that with Cr doping an additional mode is generated at around 510 cm −1 and intensity of this mode increases with increasing the Cr doping.…”

Epitaxial thin-film growth of Ruddlesden–Popper-type Ba3Zr2O7 from a BaZrO3 target by pulsed laser deposition

“…are technologically very important for numerous devices like piezoelectric transducer, transistor, dielectric resonator, dynamic random access memory (DRAMS), magnetic data storage devices, sensors, etc. [1,2] because of their variable structure and chemical composition [3]. Among the ideal cubic perovskite oxide materials, BaZrO 3 being a high-dielectric-constant material has been studied to replace silicon dioxide (SiO 2 ) gate insulator material of MOS transistors [4].…”