Produção Nacional
Phonon Raman scattering in R 1 − x A x MnO 3 +</…
1998; American Physical Society; Volume: 58; Issue: 17 Linguagem: Inglês
10.1103/physrevb.58.11435
ISSN1095-3795
AutoresE. Granado, N. O. Moreno, Ailton J. Garcia, J. A. Sanjurjo, C. Rettori, Í. Torriani, S. B. Oseroff, J. J. Neumeier, K. J. McClellan, Sang‐Wook Cheong, Y. Tokura,
Tópico(s)Iron-based superconductors research
ResumoPolarized Raman spectra of single and polycrystalline ${R}_{1\ensuremath{-}x}{A}_{x}{\mathrm{MnO}}_{3} (R=\mathrm{L}\mathrm{a},\mathrm{P}\mathrm{r};A=\mathrm{C}\mathrm{a},\mathrm{S}\mathrm{r})$ ceramic samples were studied as a function of temperature. For the rhombohedral ${\mathrm{LaMnO}}_{3.1}$ and ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3},$ the observed Raman peaks were associated with modes arising from the folding of the Brillouin zone under lattice deformation. For the orthorhombic ${\mathrm{LaMnO}}_{3.0},$ the Raman spectra are consistent with the $\mathrm{Pnma}$ structure and show an anomalous softening of the 494 and 604 ${\mathrm{cm}}^{\ensuremath{-}1}$ modes below the antiferromagnetic ordering temperature ${T}_{N}\ensuremath{\simeq}140$ K. Polycrystalline samples of ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ show a dramatic change of the Raman spectra between 100 and 160 K, which was associated with the increase of the orthorhombic distortion observed by others for $T\ensuremath{\lesssim}240$ K. Other ${R}_{1\ensuremath{-}x}{A}_{x}{\mathrm{MnO}}_{3}$ single crystals, with small orthorhombic distortions, show Raman spectra which are similar to those observed in the rhombohedral samples.
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