Raman and crystal field studies of Tb-O bonds in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>TbM</mml:mi><mml:msub><mml:mi mathvariant="normal">n</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math>

Mansouri, S.; Jandl, S.; Ballı, M.; Laverdière, J.; Fournier, P.; Dimitrov, Dimitre

doi:10.1103/physrevb.94.115109

Cited by 19 publications

(19 citation statements)

References 35 publications

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“…With decreasing temperature, between 300 K and 5 K, no additional modes appear indicating a structural phase stability of the samples. follows the anharmonic model between 300 K and 160 K but then decreases below T S ~ 150 K. The Raman intensities of the modes at 214, 601, 622, 681 cm -1 decrease significantly below T S ~ 150 K. Similar thermal behavior has also been observed for the Raman modes at ~220 cm -1 , ~ 327 cm -1 and ~ 700 cm -1 as we have recently reported in the TbMn2O5, HoMn2O5 and YMn2O5 compounds [28]. We have attributed this characteristic temperature at T S ~ 150 K to a local disorder effect induced by the splitting of R-O bonds, into short and long bonds.…”

Section: Resultssupporting

confidence: 86%

“…Each set of Raman spectra is recorded under the same experimental conditions and on the same spot of the sample. The typical phonons associated with the orthorhombic RMn2O5 manganites are observed [24,28,[30][31][32]. The assignment of the phonon symmetries refers to the previous studies in Refs.…”

Section: Resultsmentioning

confidence: 99%

“…Raman scattering and infrared measurements have been used successfully for the study of the interplay of charge, spin, and lattice degrees of freedom in manganite multifunctional materials [23][24][25][26][27]. The study of the phonon and CF excitation evolutions as a function of temperature and/or magnetic field provides interesting information regarding the magnetic and the electronic properties as well as the surrounding ligands and the local inhomogeneities [28]. In particular, the Nd 3+ , Sm 3+ and Dy 3+ Kramers ions, with odd numbers of electrons in their 4f shells, have levels with two-fold degeneracies that could be lifted in the presence of local and applied magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

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Probing the role of Nd3+ ions in the weak multiferroic character of NdMn2O5 by optical spectroscopies

et al. 2018

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Raman and infrared spectroscopies are used as local probes to study the dynamics of the Nd-O bonds in the weakly multiferroic NdMn2O5 system. The temperature dependence of selected Raman excitations reveals the splitting of the Nd-O bonds in NdMn2O5. The Nd 3+ ion crystal field (CF) excitations in NdMn2O5 single crystals are studied by infrared transmission as a function of temperature, in the 1800-8000 cm -1 range, and under an applied magnetic field up to 11 T. The frequencies of all 4 Ij crystal-field levels of Nd 3+ are determined. We find that the degeneracy of the ground-state Kramers doublet is lifted (∆0 ~7.5 cm -1 ) due to the Nd 3+ -Mn 3+ interaction in the ferroelectric phase, below TC ~ 28 K.The Nd 3+ magnetic moment mNd(T) and its contribution to the magnetic susceptibility and the specific heat are evaluated from ∆0(T) indicating that the Nd 3+ ions are involved in the magnetic and the ferroelectric ordering observed below ~ 28 K. The Zeeman splitting of the excited crystal field levels of the Nd 3+ ions at low temperature is also analyzed. dependent on the size of the rare-earth [2, 12-15]. The RMn2O5 compounds with large ionic radii (R= La and Pr) do not exhibit a detectable electric polarization and are considered as paraelectrics [14], while those with small ionic radii (R=Sm to Lu) display a finite electric polarization [13]. The intermediate size member of this family NdMn2O5 represents a particular case between the non-ferroelectric PrMn2O5 and the ferroelectric SmMn2O5. Recently, Chattopadhyay et al. [16-17] have revealed the weak ferroelectric character of this compound. The electric polarisation of NdMn2O5 (~2.4 μCm −2 ) is two orders of magnitude smaller than that of other multiferroic members of this series. Moreover, unlike the other multiferroic members of this family, its electrical polarization arises in an incommensurate magnetic state [13]. The RMn2O5 compounds crystallize in the orthorhombic structure [18-19] where edge-shared Mn 4+ O6 octahedra are connected along the c-axis and pairs of Mn 3+ O5 pyramids are linked to two Mn 4+ O6 chains. The rare earth ions are located in distorted RO8 polyhedra. However, there is no consensus on their space group symmetry. Indeed, a slight deviation from the Pbam space group has been recently observed in some compounds of this family [20]. The magnetic frustration of these systems is imposed by the geometric configuration. The loop of five adjacent Mn 3+ and Mn 4+ ions leads to a complex magnetic configuration in the RMn2O5 systems [1, 21-22]. The Mn 3+ and Mn 4+ moments are coupled antiferromagnetically by the exchange parameters J4 along the a-axis and J3 along the baxis [22]. The Mn 3+ moments, in two linked pyramids, couple antiferromagnetically via the exchange parameters J5. As a result of these numerous exchange parameters and the magnetic frustration, RMn2O5 multiferroics with small R ions show multiple phase transitions as a function of temperature. A magnetic transition to an antiferromagnetic order

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Probing the role of Nd3+ ions in the weak multiferroic character of NdMn2O5 by optical spectroscopies

et al. 2018

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“…This reduced Raman intensity can be approximated by the product , where is the density of vibrational states and a matrix element. A best fit for the phonon density of states usually results in 23 , 25 , 59 . To consider only the contribution of the monoclinic phase of VO to the Raman response, we normalized the reduced Raman intensity to the monoclinic phase fraction 25 , 58 , 59 .…”

Section: Resultsmentioning

confidence: 99%

“…Raman spectroscopy probes the local structural properties of materials based on the characteristic of their vibrational modes (frequencies, widths and intensities) and it has already been successfully used to study the coupling between charge and lattice degrees of freedom in strongly correlated electron systems 22 , 23 and observation of low-fequency spin excitation 24 . Moreover, the evolution of phonon intensities as a function of temperature provides crucial information on the electronic properties as well as the bonding covalence and the local thermal disorder.…”

Section: Introductionmentioning

confidence: 99%

Probing the role of thermal vibrational disorder in the SPT of VO$$_2$$ by Raman spectroscopy

Suleiman

Mansouri

Émond

et al. 2021

Sci Rep

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Phase competition in transition metal oxides has attracted remarkable interest for fundamental aspects and technological applications. Here, we report a concurrent study of the phase transitions in undoped and Cr-doped VO$$_2$$ 2 thin films. The structural, morphological and electrical properties of our films are examined and the microstructural effect on the metal–insulator transition (MIT) are highlighted. We further present a distinctive approach for analyzing the Raman data of undoped and Cr-doped VO$$_2$$ 2 thin films as a function of temperature, which are quantitatively correlated to the electrical measurements of VO$$_2$$ 2 films to give an insight into the coupling between the structural phase transition (SPT) and the MIT. These data are also combined with reported EXAFS measurements and a connection between the Raman intensities and the mean Debye–Waller factors $$\sigma ^2$$ σ 2 is established. We found that the temperature dependence of the $$\sigma _{R}^{2}(V-V)$$ σ R 2 ( V - V ) as calculated from the Raman intensity retraces the temperature profile of the $$\sigma _{EXAFS}^{2}(V-V)$$ σ EXAFS 2 ( V - V ) as obtained from the EXAFS data analysis. Our findings provide an evidence on the critical role of the thermal vibrational disorder in the VO$$_2$$ 2 phase transitions. Our study demonstrates that correlating Raman data with EXAFS analysis, the lattice and electronic structural dynamics can be probed.

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