Raman phonons and light scattering in RMnO3 (R=La, Pr, Nd, Ho, Er Tb and Y) orthorhombic and hexagonal manganites

Martı́n-Carrón, L.; Andrés, A. de; Martı́nez-Lope, M. J.; Casáis, M. T.; Alonso, José Antonio

doi:10.1016/s0925-8388(01)01047-7

Cited by 59 publications

(22 citation statements)

References 14 publications

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“…The polarized Raman spectra of each compound, collected using laser excitation with different photon energy in the visible region, are practically identical, which shows that the resonance effects are negligible. It is worth noting here that this could not be concluded from the previous works 3,[5][6][7][8][9] because the spectra were obtained with a single laser line. Indeed, several papers on orthorhombic YMnO 3 report polarized 3,6,9 or nonpolarized 7,8 Raman spectra, obtained with either 515 nm or 633 nm laser excitation.…”

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confidence: 81%

“…It is worth noting here that this could not be concluded from the previous works 3,5-9 because the spectra were obtained with a single laser line. Indeed, several papers on orthorhombic YMnO 3 report polarized 3,6,9 or nonpolarized 7,8 Raman spectra, obtained with either 515 nm or 633 nm laser excitation. For YCrO 3 there is only one early paper 5 on the polarized Raman spectra using 515 nm.…”

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confidence: 99%

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Comparative Raman study of isostructural YCrO3and YMnO3: Effects of structural distortions and twinning

et al. 2011

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Polarized Raman spectra of isostructural orthorhombic YCrO 3 and YMnO 3 single crystals were collected at same conditions using different laser excitation in the visible range. The symmetry of the observed lines was determined and they were assigned to definite atomic vibrations based on lattice dynamical calculations. The frequencies of the lines of the same origin in both compounds are close, however, their intensities differ significantly. While the different intensity of the modes, activated by the Jahn-Teller distortion, can be explained by the different magnitude of this distortion in the two compounds, the cause of the reduced intensity of other lines in low frequency region in the Raman spectra of YMnO 3 is likely due to the fine twinning of the crystal. INTRODUCTIONThe interest in the transition-metal perovskite-like oxides ABO 3 continues for decades because of many attractive phenomena observed in these compounds. Among them are structural second-order phase transitions, high-T c superconductivity, colossal magnetoresistance, charge-and orbital-ordering, complex magnetic properties, etc. As a rule the structural, electrical and magnetic properties of these compounds are strongly correlated. They can be tuned through the change of the mismatch of the A-O and B-O bond lengths, expressed by the tolerance factor t = (R A + R O )/ √ 2(R B + R O ), where R O , R A and R B are the ionic radii of the oxygen and atoms in the A-and B-positions, respectively. Depending on the value of t, most of these compounds crystallize in superstructures of the ideal cubic perovskite (space group Pm3m) with R3c or Pnma symmetry. Using the model of Glazer 1 , treating the BO 6 octahedra as rigid ones, the superstructures can be obtained from the ideal cubic perovskite through some tilts (rotations) of the octahedra around the main crystallographic directions. In the Glazer's notations, the rhombohedral R3c structure is of (a − a − a − ) type and the orthorhombic Pnma structure is of (a − b + a − ) type.Raman spectroscopy is a powerful experimental technique for study of perovskite-like oxides. Due to the fact that there are no Raman-active modes in the ideal cubic perovskite, all observed lines in the one-phonon region of the Raman spectra of the real perovskites have to be connected to some deviations of the real structure from the ideal one. For example, as shown in the pioneering work of Scott 2 , one of the Raman-active modes in the rare-earth aluminates of R3c structure consists in a rigid octahedral tilt around [111] direction. This mode can be considered as a "soft mode" and its frequency goes to zero as the temperature approaches the critical temperature of the structural second-order phase transition. Iliev et al. 3 have shown that in the case of rare-earth manganites with orthorhombic Pnma structure, two of the observed lines in the Raman spectra originate from modes with a shape of the two static octahedral tilts, existing in the structure. Although that these compounds do not undergo second order transition to...

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confidence: 99%

Comparative Raman study of isostructural YCrO3and YMnO3: Effects of structural distortions and twinning

et al. 2011

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“…The ~460 cm -1 peak has the B 1g or B 3g symmetry as it is induced from the selection rules [29]. This mode was previously attributed to the B 1g bending mode [28]. The ~480 cm -1 peak has the B 2g symmetry and couples with the CO state.…”

Section: Resultsmentioning

confidence: 86%

“…1a and b) and the spectra are characterized by broader features due to the JT distortion. The ~430 cm -1 (80K) peak is of B 2g symmetry and is attributed to the bending mode [28]. The ~460 cm -1 peak has the B 1g or B 3g symmetry as it is induced from the selection rules [29].…”

Section: Resultsmentioning

confidence: 99%

“…The Pnma orthorhombic PCMO compound (point group symmetry D 2h ) is structurally distorted with respect to the cubic perovskite in two ways: the MnO 6 octahedra present a strong JT cooperative distortion due to Mn +3 ions, and the octahedra are tilted in order to optimize the R-O bond lengths [28] giving 7A g + 5B 1g + 7B 2g + 5B 3g Raman active zone-center optical phonons. Figure 1 presents typical Raman spectra for the single crystal of PCMO film at various external conditions.…”

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Pressure and magnetic field effects on Pr_1–xCa_x MnO₃ thin films

Antonakos

Filippi

Auban‐Senzier

et al. 2009

Physica Status Solidi (b)

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We report a systematic study of Pr1–x Cax MnO3 (x = 0.4 and 0.6) thin films grown on LaAlO3 (LAO) substrate (PCMO/LAO). X‐ray diffraction measurements have shown that the PCMO/LAO film is [101]‐oriented and under compressive strain due to the lattice mismatch. According to Raman spectroscopy the Jahn–Teller modes are suppressed under the application of pressure in the PCMO (x = 0.4) thin film. In particular, it was found that a pressure of 2 GPa suppresses the charge ordered state. Further high pressure measurements have confirmed that resistivity decreases linearly up to 2.4 GPa corresponding to a total reduction of about 35% in resistivity leading to a more conductive state on both concentrations. The temperature dependence of the resistivity has shown that the samples under pressure retain their semiconducting behavior. At ambient pressure the PCMO (x = 0.6) film shows a moderate magnetoresistance in the range 0–7 T and no metal to insulator transition (MIT). Raman spectroscopy confirmed that the application of a magnetic field of 1 T does not induce any remarkable changes on the electron–phonon interaction. Although, the hydrostatic pressure is not enough to induce a macroscopic metallic state, its effect is much greater than the one of the magnetic field. In addition, the effect of the 7 T magnetic field appears the same at ambient pressure and 2.5 GPa. Therefore the two effects of hydrostatic pressure and magnetic field do not seem to be coupled, at least up to the magnitudes studied. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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SO₂ Resisting Pd‐doped Pr_1‐xCe_xMnO₃ Perovskites for Efficient Denitration at Low Temperature

Cao

et al. 2021

Chemistry An Asian Journal

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H2‐SCR is served as the promising technology for the controlling of NOx emission, and the Pd‐based derivative catalyst exhibited high NOx reduction performance. Effectively regulating the electronic configuration of the active component is favorable to the rational optimization of noble Pd. In this work, a series of Pr1‐xCexMn1‐yPdyO3@Ni were successfully synthesized and exhibited superior NO conversion efficiency at low temperatures. 92.7 % conversion efficiency was achieved at 200 °C over Pr0.9Ce0.1Mn0.9Pd0.1O3@Ni in the presence of 4 % O2 with a GHSV of 32000 h−1. Meanwhile, the outstanding performance was obtained in the resistance to SO2 (200 ppm) and H2O (8 %). Deduced from the results of XRD, Raman, XPS, and H2‐TPR, the modification of d orbit states in palladium was confirmed originating from the incorporation in the B site of Pr0.9Ce0.1Mn0.9Pd0.1O3. The existence of higher valence (Pd3+ and Pd4+) than the bivalence in Pr0.9Ce0.1Mn0.9Pd0.1O3 catalyst was evidenced by XPS analysis. Our research provides a new sight into the H2‐SCR through the higher utilization of Pd.

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Raman phonons and light scattering in RMnO3 (R=La, Pr, Nd, Ho, Er Tb and Y) orthorhombic and hexagonal manganites

Cited by 59 publications

References 14 publications

Comparative Raman study of isostructural YCrO3and YMnO3: Effects of structural distortions and twinning

Comparative Raman study of isostructural YCrO3and YMnO3: Effects of structural distortions and twinning

Pressure and magnetic field effects on Pr_1–xCa_x MnO₃ thin films

SO₂ Resisting Pd‐doped Pr_1‐xCe_xMnO₃ Perovskites for Efficient Denitration at Low Temperature

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Raman phonons and light scattering in RMnO3 (R=La, Pr, Nd, Ho, Er Tb and Y) orthorhombic and hexagonal manganites

Cited by 59 publications

References 14 publications

Comparative Raman study of isostructural YCrO3and YMnO3: Effects of structural distortions and twinning

Comparative Raman study of isostructural YCrO3and YMnO3: Effects of structural distortions and twinning

Pressure and magnetic field effects on Pr1–xCax MnO3 thin films

SO2 Resisting Pd‐doped Pr1‐xCexMnO3 Perovskites for Efficient Denitration at Low Temperature

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Pressure and magnetic field effects on Pr_1–xCa_x MnO₃ thin films

SO₂ Resisting Pd‐doped Pr_1‐xCe_xMnO₃ Perovskites for Efficient Denitration at Low Temperature