Effect of phonon anharmonicity on ferroelectricity in 
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Poojitha, Bommareddy; Rubi, Km; Sarkar, Soumya; Mahendiran, R.; Venkatesan, T.; Saha, Surajit

doi:10.1103/physrevmaterials.3.024412

Cited by 21 publications

(22 citation statements)

References 43 publications

(20 reference statements)

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“…Along these lines, we like to stress again that the scope of the presented method goes beyond thermal transport and phase transition mechanisms, and potentially applies to any phenomenon governed by anharmonic effects such as free energies [53], thermal expansion [54], thermal stability [55], defect formation [56,57], ferroelectricity [58], and electronphonon coupling [59]. Further investigations are expected to reveal useful relationship between σ A and these target properties, as the thermal conductivities example above showcases.…”

Section: Discussionmentioning

confidence: 86%

Anharmonicity measure for materials

Knoop

Purcell

Scheffler

et al. 2020

Phys. Rev. Materials

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Theoretical frameworks used to qualitatively and quantitatively describe nuclear dynamics in solids are often based on the harmonic approximation. However, this approximation is known to become inaccurate or to break down completely in many modern functional materials. Interestingly, there is no reliable measure to quantify anharmonicity so far. Thus, a systematic classification of materials in terms of anharmonicity and a benchmark of methodologies that may be appropriate for different strengths of anharmonicity is currently impossible. In this work, we derive and discuss a statistical measure that reliably classifies compounds across temperature regimes and material classes by their "degree of anharmonicity." This enables us to distinguish "harmonic" materials, for which anharmonic effects constitute a small perturbation on top of the harmonic approximation, from strongly "anharmonic" materials, for which anharmonic effects become significant or even dominant and the treatment of anharmonicity in terms of perturbation theory is more than questionable. We show that the analysis of this measure in real and reciprocal space is able to shed light on the underlying microscopic mechanisms, even at conditions close to more complicated dynamical processes, e.g., phase transitions or defect formation. Eventually, we demonstrate that the developed approach is computationally efficient and enables rapid high-throughput searches by scanning over a set of several hundred binary solids. The results show that strong anharmonic effects beyond the perturbative limit are not only active in complex materials or close to phase transitions, but already at moderate temperatures in simple binary compounds.

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Section: Discussionmentioning

confidence: 86%

Anharmonicity measure for materials

Knoop

Purcell

Scheffler

et al. 2020

Phys. Rev. Materials

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“…Based on the information provided in Poojitha et al [ 28 ] we suspect that the broad bands are the result of the high laser power used in these studies. Figure S3 clearly evidences the effect of overheating on our samples: starting from a featureless Raman spectrum, consistent with the cubic space group, broad bands appear with increased laser power, similar to those observed in Poojitha et al [ 28 ] (which remain when laser power is reduced). From this observation we conclude that the observed modes detected are caused by oxidation of the ETO.…”

Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

“…Recently, an experimental study of ETO polycrystalline samples [ 28 ] revealed broad Raman bands even at room temperature (as in SrTiO 3 [ 7,8 ] ), which were almost temperature independent. Based on the information provided in Poojitha et al [ 28 ] we suspect that the broad bands are the result of the high laser power used in these studies. Figure S3 clearly evidences the effect of overheating on our samples: starting from a featureless Raman spectrum, consistent with the cubic space group, broad bands appear with increased laser power, similar to those observed in Poojitha et al [ 28 ] (which remain when laser power is reduced).…”

Section: Resultsmentioning

confidence: 99%

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Magnetic interactions and the puzzling absence of any Raman mode in EuTiO₃

Pappas

Liarokapis

Calamiotou

et al. 2021

J Raman Spectroscopy

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Polycrystalline ceramic samples and a single crystal of EuTiO3 have been investigated by Raman spectroscopy in the temperature range 80–300 K. Although synchrotron x‐ray diffraction (XRD) data clearly indicated the cubic to tetragonal phase transition around 282 K, no mode from the symmetry allowed Raman active phonons was found in the tetragonal phase, contrary to the case of the homologous SrTiO3. In order to study the evolution of this unique characteristic, ceramics of EuxSr1‐xTiO3 (x = 0.03–1.0) characterized by synchrotron XRD for the structural phase transition have been also investigated by Raman spectroscopy, verifying the very strong influence on the Raman yield by Eu substitution. By applying an external magnetic field or alternatively hydrostatic pressure modes are activated in the Raman spectra. Temperature dependant XAS/XMCD measurements indicate the presence of magnetic interactions even close to room temperature in agreement with previous experimental results also showing the presence of small magnetic interactions deep inside the paramagnetic phase. A possible explanation for the puzzling absence of the Raman modes is proposed related to a strong spin–lattice interaction that drives the cubic to tetragonal structural phase transition and makes the Raman tensor antisymmetric. In this model, the external perturbation will induce a symmetric Raman tensor allowing modes to be present in the spectra.

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“…They have attributed the observed correlation between magnetic and dielectric responses to the possible spin-phonon coupling in 15R-BaMnO3. Since phonons play a major role in ferroelectric materials [16][17][18], one may expect them to have an equally important role in the magnetoelectric multiferroics too. A detailed understanding of the phonons and their coupling is, therefore, extremely important as it extends the opportunity to engineer new functionalities in transition metal oxides such as BaMnO3 and others.…”

Section: Introductionmentioning

confidence: 99%

Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal15R−BaMnO3

et al. 2020

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Spin-phonon coupling, the interaction of spins with surrounding lattice is a key parameter to understand the underlying physics of multiferroics and engineer their magnetization dynamics. Elementary excitations in multiferroic materials are strongly influenced by spin-phonon interaction, making Raman spectroscopy a unique tool to probe these coupling(s). Recently, it has been suggested that the dielectric and magnetic properties of 15R-type hexagonal BaMnO3 are correlated through the spin-lattice coupling. Here, we report the observation of an extensive renormalization of the Raman spectrum of 15R-BaMnO3 at 230 K, 280 K, and 330 K. Magnetic measurements reveal the presence of a long-range and a short-range magnetic ordering in 15R-BaMnO3 at 230 K and 330 K, respectively. The Raman spectrum shows the appearance of new Raman modes in the magnetically ordered phases. Furthermore, an additional Raman phonon appears below ~ 280 K, possibly arising from a local latticedistortion due to the displacement of Mn-ions, that exhibits anomalous shift with temperature. The origin of the observed renormalization and phonon anomalies in Raman spectra are discussed based on the evidences from temperature-and magnetic-field-dependent Raman spectra, temperature-dependent x-ray diffraction, magnetization, and specific heat measurements. Our results indicate the presence of magnetostriction and spin-phonon coupling in 15R-BaMnO3 thus suggesting that the optical phonons are strongly correlated to its magnetoelectric properties.

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Effect of phonon anharmonicity on ferroelectricity in EuxBa1−xTiO3

Cited by 21 publications

References 43 publications

Anharmonicity measure for materials

Anharmonicity measure for materials

Magnetic interactions and the puzzling absence of any Raman mode in EuTiO₃

Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal15R−BaMnO3

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Effect of phonon anharmonicity on ferroelectricity in EuxBa1−xTiO3

Cited by 21 publications

References 43 publications

Anharmonicity measure for materials

Anharmonicity measure for materials

Magnetic interactions and the puzzling absence of any Raman mode in EuTiO3

Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal15R−BaMnO3

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Product

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Magnetic interactions and the puzzling absence of any Raman mode in EuTiO₃