Raman scattering study of Nd_1 xSr_xMnO₃(x  0.3, 0.5)

Abstract

We report on polarized Raman scattering of single crystals of Nd 1−x Sr x MnO 3 (x = 0.3, 0.5). Raman spectra of Nd 0.7 Sr 0.3 MnO 3 show a significant change through the metal-insulator transition. In the ferromagnetic metallic phase phonon modes grow in intensity and number while the electronic continuum becomes more pronounced. We suggest that these effects are due to the strong competition between the localization and the delocalization of carriers which is the origin of the largest colossal magnetoresistance effect ever reported for the manganites. Raman spectra of Nd 0.5 Sr 0.5 MnO 3 , upon cooling through the charge-ordering temperature T C O = 148 K, exhibit several new lines which undergo a substantial hardening. This hardening is interpreted as a freezing of the Jahn-Teller distortions with a gradual decrease of a fraction of the ferromagnetic phase in the CE-type charge/orbital ordered state.

Zone center frequencies of the orthorhombic NdMnO3 perovskite

“…Recently, the polarized Raman spectra were recorded by Jandl et al [5] and they had assigned the observed frequencies to 10 Raman modes. It should be mentioned that Raman frequencies were also measured in case of Nd 0.7 Sr 0.3 MnO 3 by Choi et al [6]. In the present paper, an attempt has been made to study the zone center phonons in NdMnO 3 for the first time using a short range force constant model and then based on the atomic vibrations, the specific modes assigned in the experimental studies of Raman frequencies [5] were confirmed and for infrared frequencies assigned.…”

“…One should note that each of the eigen vectors have three components, which makes The experimental values at 4.2 K obtained by Jandl et al [5] and Choi et al [6] for Nd 0.7 Sr 0.3 MnO 3 at 5 K are also shown. the table very lengthy and hence only the length of the total displacements are provided in the table.…”

Effect of iron doping on the physical properties of europium manganites

“…The assignment of these modes is based on the lattice dynamic calculation [35] and similar to Choi et al [38]. The low-frequency mode at 210 cm −1 is attributed to the A 1g mode, which is the inphase rotation of the oxygen cage about the y-axis to adjacent MnO 6 octahedra.…”

Synthesis of Pr0.70Sr0.30MnO3δ and Nd0.70Sr0.30MnO3δ powders by solution-combustion technique

“…The Pr 3+ ion has an ionic radius of 0.990 Å and Nd 3+ ion has an ionic radius of 0.983 Å, while the ionic radius of the Sr 2+ ion is 1.180 Å. Because the ionic radius of the Sr 2+ ion is larger than Pr 3+ or Nd 3+ ions, there is a limitation and substitution these ions for Sr in the structures (15) .…”