Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO<sub>3</sub>at Low Temperatures Using Picosecond Ultrasound Spectroscopy

Nagakubo, Akira; Yamamoto, Akihiro; Tanigaki, Kenichi; Ogi, Hirotsugu; Nakamura, Nobutomo; Hirao, Masahiko

doi:10.7567/jjap.51.07ga09

Cited by 16 publications

(11 citation statements)

References 30 publications

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“…Below 323 K, the LA phonon shows anomalous behavior with a sharp minimum in the frequency followed by a sharp maximum in width at the ferroelastic phase transition temperature T ct = 280 K [ 83 ]. Similar elastic anomalies are observed in nondoped SrTiO 3 crystal by picosecond ultrasound spectroscopy [ 84 ]. The remarkable increase in T ct by Ca doping can be caused by the smaller ionic radius of Ca ions, which induces the antiferro distortive rigid rotation of the oxygen octahedral [ 85 ].…”

Section: Resultssupporting

confidence: 80%

Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals

2023

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Compositionally disordered perovskite compounds have been one of the exotic topics of research during the past several years. Colossal piezoelectric and electrostrictive effects have been observed in disordered perovskite ferroelectric materials. The key ingredient in the physical behavior of disordered perovskites is the nucleation and growth of the local dipolar regions called polar nanoregions (PNRs). PNRs begin to nucleate far above the temperature of the dielectric maximum Tm and exhibit varied relaxation behavior with temperature. The evidence for the existence of various stages in the relaxation dynamics of PNRs was revealed through the study of the temperature evolution of optical phonons by Raman scattering. The quasi-static regime of PNRs is characterized by the strong coupling between the local polarization and strain with the local structural phase transition and the critical slowing of the relaxation time. Strong anomalies in the frequency and the width of the acoustic phonons, and emergence of the central peak in the quasi-static region of the relaxation dynamics of PNRs have been observed through Brillouin scattering studies. In this review, we discuss the anomalies observed in Brillouin scattering in selected disordered perovskite ferroelectrics crystals such as Pb(Mg1/3Ta2/3)O3, Pb(Sc1/2Ta1/2)O3, 0.65PIN-0.35PT and Sr0.97Ca0.03TiO3 to understand dynamical behavior of PNRs.

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Section: Resultssupporting

confidence: 80%

Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals

2023

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“…Since the generation of the acoustic phonons is due to the pump‐induced lattice expansion, the amplitude of the acoustic phonons ( A osc ) is proportional to change of lattice constants Δ b . If we only take the lattice heating effect into consideration, according to the previous reports in La 1−x Ca x MnO 3 ( x = 0.5, 0.58) and Pt/SrTiO 3 , the Δ b is expected to increase with the increase of T . However, the A osc in our measurements as shown in Figure (b) decreases with increasing T , showing that the small polarons can suppress the A osc .…”

contrasting

confidence: 55%

Observation of Small Polaron and Acoustic Phonon Coupling in Ultrathin La_0.7Sr_0.3MnO₃/SrTiO₃ Structures

Liu

Niu

Ruan

et al. 2019

Physica Rapid Research Ltrs

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Understanding the underlying physics of interactions among various quasi‐particles is a fundamental issue for the application of spintronics and photonics. Here the observation of a coupling between the small polarons in the nanoscale ultrathin La0.7Sr0.3MnO3 (LSMO) films and the acoustic phonons in the SrTiO3 (STO) substrate using ultrafast pump–probe spectroscopy has been reported. According to the temperature‐ and wavelength‐dependent measurements, the amplitudes of the acoustic phonons are suppressed by tuning the small polarons absorption. This shows a coupled relationship between the acoustic phonons and the small polarons. At the probe photon energy of 1.55 eV where the polaron absorption is dominant, the acoustic phonons become unobservable. Furthermore, by performing the pump fluence dependent measurements on the LSMO films with different thicknesses, smaller acoustic phonon amplitudes are found in the thinner film with stronger small polaron binding energy. Such a coupled nature can be utilized to manipulate the small polarons using the acoustic phonons or vice versa, which is of great importance in device applications of colossal magnetoresistance materials.

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“…Both light normally entered a specimen through an objective lens. 48 The pump light pulse excites a strain pulse at the film surface, which leads to through-thickness resonances or pulse-echo signals for the 40-nm or 70-nm films, respectively (in Fig. S2).…”

mentioning

confidence: 99%

Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory

Nagakubo

Lee

Ogi

et al. 2020

Applied Physics Letters

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Tungsten thin films are used for various applications and sometimes exhibit an A15 structure (b-W). They have some superior properties in comparison to the bcc structure (a-W), such as a higher superconducting transition temperature and larger spin Hall angle. However, elastic constants of b-W are unclear, which restricts mechanical applications and reliable density-functional-theory calculations. In this study, we synthesized a-W, b-W, and mixed-phase W films and determined their elastic constants by picosecond ultrasonics. We also calculated the elastic constants based on density functional theory and reveal that b-W has a larger elastic anisotropy and smaller shear modulus. Our calculation further indicates a stable stacking faulted b-W, which leads to a monoclinic structure.

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Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO₃at Low Temperatures Using Picosecond Ultrasound Spectroscopy

Cited by 16 publications

References 30 publications

Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals

Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals

Observation of Small Polaron and Acoustic Phonon Coupling in Ultrathin La_0.7Sr_0.3MnO₃/SrTiO₃ Structures

Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory

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Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO3at Low Temperatures Using Picosecond Ultrasound Spectroscopy

Cited by 16 publications

References 30 publications

Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals

Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals

Observation of Small Polaron and Acoustic Phonon Coupling in Ultrathin La0.7Sr0.3MnO3/SrTiO3 Structures

Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory

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Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO₃at Low Temperatures Using Picosecond Ultrasound Spectroscopy

Observation of Small Polaron and Acoustic Phonon Coupling in Ultrathin La_0.7Sr_0.3MnO₃/SrTiO₃ Structures