Dielectric Constant of Strontium Titanate at Low Temperatures

Sawaguchi, E.; Kikuchi, Atsushi; Kodera, Yōichi

doi:10.1143/jpsj.17.1666

Cited by 170 publications

(62 citation statements)

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“…9 They should demonstrate also very short response time comparable with the period of the lattice soft mode oscillations and the microwave 4 GHz intermodulation distortion measurements ͑subnano-second scale of response time͒ 10 and nanosecond pulse measurements 11 appeared to confirm this. However, a more careful analysis of the experimental results 11 revealed a difference between the variation of dielectric constant under ac and dc voltages, with a dc voltage producing a greater change in dielectric constant.…”

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confidence: 75%

Enhanced electrical properties of ferroelectric thin films by ultraviolet radiation

Alford

Petrov

Gagarin

et al. 2005

Applied Physics Letters

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Ferroelectric films in the paraelectric phase exhibit two undesirable properties: hysteresis in the voltage-capacitance characteristics and a significant relaxation time of the capacitance. Our experiments show that suppression of both of these is achieved by using UV radiation with wavelengths corresponding to the material forbidden gap. Experimentally we also observed UV radiation induced modulation of thin film permittivity without an applied electric field. The observed phenomena are believed to have the same origin: UV light generates nonequilibrium charge carriers that screen out local electric field induced by defects and interfaces inside ferroelectric thin films and change films effective dielectric properties. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.2137466͔ Ferroelectric materials have been the subject of extensive research for over 50 years. However, recent investigations of thin films of SrTiO 3 , BaTiO 3 , and their solid solution Ba x Sr 1−x TiO 3 ͑BSTO͒, motivated by the prospect of new applications such as electrically controllable microwave devices, 1,2 have uncovered many complexities not previously recognized. The most effort has been aimed at the optimization of thin film fabrication processes, i.e., to the microwave loss reduction ͑microwave loss tangent of ferroelectric thin films is much higher than that of corresponding bulk crystals͒, 3,4 increasing the tunability, 5 and improving the temperature stability. 6,7 These points are now better understood, but the issue of the residual polarization and the hysteresis phenomenon observed under varying bias voltage, resulting in slow relaxation of dielectric constant of ferroelectric films in paraelectric phase ͑above the Curie temperature͒, 8 has not been properly addressed.In principle, ferroelectric materials in the paraelectric phase should not exhibit hysteresis in the C͑V͒ behavior ͑voltage-capacitance characteristics͒. 9 They should demonstrate also very short response time comparable with the period of the lattice soft mode oscillations and the microwave 4 GHz intermodulation distortion measurements ͑subnano-second scale of response time͒ 10 and nanosecond pulse measurements 11 appeared to confirm this. However, a more careful analysis of the experimental results 11 revealed a difference between the variation of dielectric constant under ac and dc voltages, with a dc voltage producing a greater change in dielectric constant. The varactors' fast switching is at the expense of a decreased tunability. Furthermore, the difference between the variation of dielectric constant under ac and dc voltages varied with the magnitude of the applied voltage pulses, their duration and their repetition time making the control of devices problematic. Overcoming this problem will enable broader application of the ferroelectrics in microwave electronics.There exist a number of models explaining the residual polarization and dielectric relaxation in ferroelectric thin films. The charge injection 12 and space charge formation ͑migration of oxyg...

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confidence: 75%

Enhanced electrical properties of ferroelectric thin films by ultraviolet radiation

Alford

Petrov

Gagarin

et al. 2005

Applied Physics Letters

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“…18,19 The internal electric field at the LAO/STO interface, for example, is somewhere between 1 -10 mV/Å [19][20][21][22][23][24] , which 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 …”

Section: Model and Methodsmentioning

confidence: 99%

Electronic phases and phase separation in the Hubbard-Holstein model of a polar interface

Nanda

Satpathy

2011

Phys. Rev. B

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From a mean-field solution of the Hubbard-Holstein model, we show that a rich variety of different electronic phases can result at the interface between two polar materials such as LaAlO3/SrTiO3. Depending on the strengths of the various competing interactions, viz., the electronic kinetic energy, electron-phonon interaction, Coulomb energy, and electronic screening strength, the electrons could (i) either be strongly confined to the interface forming a 2D metallic or an insulating phase, (ii) spread deeper into the bulk making a 3D phase, or (iii) become localized at individual sites forming a Jahn-Teller polaronic phase. In the polaronic phase, the Coulomb interaction could lead to unpaired electrons resulting in magnetic Kondo centers. Under appropriate conditions, electronic phase separation may also occur resulting in the coexistence of metallic and insulating regions at the interface.

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“…They exhibit a wide range of novel magnetic, dielectric, and transport properties: for example, the large negative magnetoresistance in La 1−x Sr x MnO 3 [3][4][5], the spin-state transition in La 1−x Sr x CoO 3 [6,7], the metalto-insulator transition in RNiO 3 (R: rare earth element) [8], and the ferroelectric to quantum paraelectric transition in Ba 1−x Sr x TiO 3 [9,10]. In these phenomena, the central players are the electrons in 3d orbitals of the B-site TMs hybridized with oxygen 2p orbitals.…”

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confidence: 99%

Theory of Valence Transition inBiNiO3

2016

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Motivated by the colossal negative thermal expansion recently found in BiNiO3, the valence transition accompanied by the charge transfer between the Bi and Ni sites is theoretically studied. We introduce an effective model for Bi-6s and Ni-3d orbitals with taking into account the valence skipping of Bi cations, and investigate the ground-state and finite-temperature phase diagrams within the mean-field approximation. We find that the valence transition is caused by commensurate locking of the electron filling in each orbital associated with charge and magnetic orderings, and the critical temperature and the nature of the transitions are strongly affected by the relative energy between the Bi and Ni levels and the effective electron-electron interaction in the Bi sites. The obtained phase diagram well explains the temperature-and pressure-driven valence transitions in BiNiO3 and the systematic variation of valence states for a series of Bi and Pb perovskite oxides. PACS numbers: 71.10.Fd , 71.30.+h , 75.25.Dk, 75.30.Kz Perovskite transition metal (TM) oxides (general formula: ABO 3 ) have been providing central issues of phase transitions and strong electron correlations in condensed matter physics [1,2]. They exhibit a wide range of novel magnetic, dielectric, and transport properties: for example, the large negative magnetoresistance in La 1−x Sr x MnO 3 [3-5], the spin-state transition in La 1−x Sr x CoO 3 [6,7], the metalto-insulator transition in RNiO 3 (R: rare earth element) [8], and the ferroelectric to quantum paraelectric transition in Ba 1−x Sr x TiO 3 [9, 10]. In these phenomena, the central players are the electrons in 3d orbitals of the B-site TMs hybridized with oxygen 2p orbitals. The A-site cations, on the other hand, are usually inert and have been regarded as "stagehands": they control the electron filling and bandwidth through their valence state and ionic radius, respectively.Peculiar exceptions to the above standards have recently been found in several perovskite TM oxides, in which the Asite cations play an active role as "valence skipper". In these compounds, not only the B-site 3d electrons but also the valence s electrons in the A-site cations significantly contribute to the electronic properties. In the valence skippers, the outermost s orbital prefers closed-shell configurations s 0 or s 2 , and tends to skip the intermediate valence s1 . This is attributed to the effective attractive interaction between s electrons [11][12][13], and hence the A-site valence state can be actively controlled through electronic degrees of freedom. Owing to the multiple electronic instabilities in both A-and B-site cations, the TM oxides with the A-site valence skipper have a potential of new electronic phases and functions.The colossal negative thermal expansion (CNTE) material BiNiO 3 [14] is one of such candidates; both Bi-6s and Ni3d electrons are expected to play a key role in the large volume change [15,16] [15,18,19]. Under pressure, this phase transition is also observed by raising temperature ...

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Dielectric Constant of Strontium Titanate at Low Temperatures

Cited by 170 publications

References 5 publications

Enhanced electrical properties of ferroelectric thin films by ultraviolet radiation

Enhanced electrical properties of ferroelectric thin films by ultraviolet radiation

Electronic phases and phase separation in the Hubbard-Holstein model of a polar interface

Theory of Valence Transition inBiNiO3

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