Femtosecond time-resolved spectroscopy of soft modes in structural phase transitions of perovskites

Dougherty, Thomas P.; Wiederrecht, Gary P.; Nelson, Keith A.; Garrett, M. H.; Jenssen, H. P.; Warde, Cardinal

doi:10.1103/physrevb.50.8996

Cited by 74 publications

(46 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Inelastic light scattering results [21,22,23] complexified this picture, by evidencing a "central peak" owing to a relaxational mode, in O-, T-KNbO 3 , T-and C-BaTiO 3 . This mode was interpreted from the 8-sites model as due to thermally activated jumps between unsymmetrical [22,23] positions of the Ti or Nb atoms.…”

mentioning

confidence: 89%

See 1 more Smart Citation

High-Pressure Study of X-Ray Diffuse Scattering in Ferroelectric Perovskites

et al. 2007

View full text Add to dashboard Cite

We present a high-pressure x-ray diffuse scattering study of the ABO3 ferroelectric perovskites BaTiO3 and KNbO3. The well-known diffuse lines are observed in all the phases studied. In KNbO3, we show that the lines are present up to 21.8 GPa, with constant width and a slightly decreasing intensity. At variance, the intensity of the diffuse lines observed in the cubic phase of BaTiO3 linearly decreases to zero at ∼ 11 GPa. These results are discussed with respect to x-ray absorption measurements, which leads to the conclusion that the diffuse lines are only observed when the B atom is off the center of the oxygen tetrahedron. The role of such disorder on the ferroelectric instability of perovskites is discussed. Because of the simplicity of their structure and their actual or potential applications, perovskites ABO 3 and their derivatives are amongst the most studied compounds in solid state science. Perovskites stabilize a large variety of states such as superconductivity, ferroelectricity (FE) and multiferroism, but despite decades of studies, the mechanisms of these transitions are still a matter of debate [1]. This is the case of the oxygen perovskites such as SrTiO 3 and KTaO 3 , which only exhibit incipient FE, while PbTiO 3 , BaTiO 3 and KNbO 3 stabilize this instability in well defined series of FE transitions.Upon heating at ambient pressure, barium titanate and potassium niobate undergo the same famous sequence of rhomboedric-orthorhombic-tetragonal-cubic (R-O-T-C) first-order phase transitions [2,3]. During this sequence, the polarization changes direction from the [111], to the [110] and [100] pseudo-cubic directions, before vanishing above the Curie temperature T C in the cubic phase. The mechanism of this sequence of phase transition has been often discussed from two limiting cases: the soft mode -or displacive -theory, in which a transverse optical (TO) mode frequency gradually soften when approaching the phase transition [4], and an order-disorder scenario [5], in which some atoms lying on symmetryequivalent sites, order on preferential ones. In fact, current theories favor an intermediate situation, in which soft phonons and disorder play a role [6,7].Pressure has proven to be an essential parameter to study phase transitions in perovskites [8]. Because applying pressure results in a symmetrization of chemical bonds, drastic effects on order-disorder phase transitions are expected. Indeed, the same sequence of phase transitions is observed as a function of pressure in KNbO 3 and BaTiO 3 [9]. At 300 K, FE is lost at 10 GPa (2 GPa) and is no more observed at low temperature above ∼ 26 GPa (∼ 6.5 GPa) in KNbO 3 (BaTiO 3 ). The existence of the O-T transition under pressure has been questioned in KNbO 3 [10], while in other studies its transition pressure was found at 6 GPa [11] or 8.5 GPa [9]. In this letter, we will show that high pressure x-ray diffuse scattering measurements give a unique opportunity to study the transitions and the FE instability as a function of the nature and the position of...

show abstract

mentioning

confidence: 89%

“…This mode was interpreted from the 8-sites model as due to thermally activated jumps between unsymmetrical [22,23] positions of the Ti or Nb atoms.…”

mentioning

confidence: 99%

High-Pressure Study of X-Ray Diffuse Scattering in Ferroelectric Perovskites

et al. 2007

View full text Add to dashboard Cite

show abstract

“…The problem of the low-frequency E-symmetry mode in tetragonal BTO was carefully studied by polariton Raman technique reviewed by Nakamura [54] who strongly supported its displacive (oscillatory) picture even though it is strongly overdamped in the limit of short polariton wavelengths. The low-frequency modes of both symmetries were also carefully studied by Dougherty et al [55] using impulsive stimulated Raman scattering. They have accurately determined the overdamped E-symmetry soft-mode parameters, i.e.…”

Section: Tetragonal Ferroelectric Phasementioning

confidence: 99%

“…The clamped ε c a response decreases on heating monotonically to about 1400 near 125 • C [56] or to still smaller values [46]. Similar behavior follows from the phonon contribution [51,55]. Appearance of any mode softening and/or central-mode dispersion is therefore possible only very close to T C and the increase in the clamped permittivity from the ferroelectric side was never quantitatively evaluated, since it might appear only very close to T C (5-10 K).…”

Section: Tetragonal Ferroelectric Phasementioning

confidence: 99%

Soft Mode Behavior in Cubic and Tetragonal BaTiO₃Crystals and Ceramics: Review on the Results of Dielectric Spectroscopy

Petzelt

2008

Ferroelectrics

View full text Add to dashboard Cite

“…The interaction with below-bandgap excitation has been intensively studied, revealing an impulsive stimulated Raman scattering process (ISRS) for the excitation of the lattice. Dougherty and coworkers [20,21] have shown that the selective excitation of transverse optical phonons shows the signature of mode softening close to the phase transition.…”

Section: Laser-induced Lattice Changesmentioning

confidence: 99%

Lattice Dynamics of Laser Excited Ferroelectric BaTiO₃

Issenmann¹,

Schleef²,

Ibrahimkutty³

et al. 2012

Acta Phys. Pol. A

View full text Add to dashboard Cite

We investigated the lattice dynamics of the prototypic ferroelectric barium titanate close to its ferroelectric--paraelectric phase transition aiming at a better understanding of the atomistic nature of the transition. The usage of time-resolved X-ray techniques allows to disentangle lattice motion and unit cell changes, which, in part, relate to the ferroelectric polarization. In the quasi-static case both the electrical and the laser excitation show a mean-field, simple thermal behaviour, while for time scales shorter than nanoseconds the impulsive nature of the excitation becomes visible.

show abstract

Femtosecond time-resolved spectroscopy of soft modes in structural phase transitions of perovskites

Cited by 74 publications

References 41 publications

High-Pressure Study of X-Ray Diffuse Scattering in Ferroelectric Perovskites

High-Pressure Study of X-Ray Diffuse Scattering in Ferroelectric Perovskites

Soft Mode Behavior in Cubic and Tetragonal BaTiO₃Crystals and Ceramics: Review on the Results of Dielectric Spectroscopy

Lattice Dynamics of Laser Excited Ferroelectric BaTiO₃

Contact Info

Product

Resources

About

Femtosecond time-resolved spectroscopy of soft modes in structural phase transitions of perovskites

Cited by 74 publications

References 41 publications

High-Pressure Study of X-Ray Diffuse Scattering in Ferroelectric Perovskites

High-Pressure Study of X-Ray Diffuse Scattering in Ferroelectric Perovskites

Soft Mode Behavior in Cubic and Tetragonal BaTiO3Crystals and Ceramics: Review on the Results of Dielectric Spectroscopy

Lattice Dynamics of Laser Excited Ferroelectric BaTiO3

Contact Info

Product

Resources

About

Soft Mode Behavior in Cubic and Tetragonal BaTiO₃Crystals and Ceramics: Review on the Results of Dielectric Spectroscopy

Lattice Dynamics of Laser Excited Ferroelectric BaTiO₃