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Your search keyword '"Yamada, Yasusada"' showing total 146 results
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146 results on '"Yamada, Yasusada"'

1. Spontaneous symmetry breaking of domain walls in phase-competing regions

Author

Ishizuka, Hiroaki, Yamada, Yasusada, and Nagaosa, Naoto

Subjects
Condensed Matter - Statistical Mechanics, Condensed Matter - Strongly Correlated Electrons
Abstract

We study the nature of domain walls in an ordered phase in the phase-competing region of two Ising-type order parameters. Considering a two-component $\phi^4$ theory, we show that the domain wall of the ground-state (primary) order parameter shows a second-order phase transition associated with the secondary order parameter of the competing phase; the effective theory of the phase transition is given by the Landau theory of Ising-type phase transition. We find that the phase boundary of this phase transition is different from the spinodal line of the competing order. Experimentally, the phase transition is detected by the divergence of the susceptibility corresponding to the secondary order when the temperature is quenched to introduce the domain walls., Comment: 4 pages, 4 figures

Published
2018
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2. A Theory of Ferroelectric Phase Transition in SrTiO$_3$ induced by Isotope Replacement

Author

Yamada, Yasusada, Todoroki, Norikazu, and Miyashita, Seiji

Subjects
Condensed Matter - Statistical Mechanics
Abstract

A theory to describe the dielectric anomalies and the ferroelectric phase transition induced by oxygen isotope replacement in SrTiO$_3$ is developed. The proposed model gives consistent explanation between apparently contradictory experimental results on macroscopic dielectric measurements versus microscopic lattice dynamical measurements by neutron scattering studies. The essential feature is described by a 3-state quantum order-disorder system characterizing the degenerated excited states in addition to the ground state of TiO$_6$ cluster. The effect of isotope replacement is taken into account through the tunneling frequency between the excited states. The dielectric properties are analyzed by the mean field approximation (MFA), which gives qualitative agreements with experimental results throughout full range of the isotope concentration.The phase diagram in the temperature-tunneling frequencycoordinate is studied by a QMC method to confirm the qualitative validity of the MFA analysis., Comment: 26 pages, 8 figures

Published
2003
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3. Symmetry of high-piezoelectric Pb-based complex perovskites at the morphotropic phase boundary I. Neutron diffraction study on Pb(Zn1/3Nb2/3)O3 -9%PbTiO3

Author

Uesu, Yoshiaki, Matsuda, Masaaki, Yamada, Yasusada, Fujishiro, Kouji, Cox, Dave E., Noheda, Beatriz, and Shirane, Gen

Subjects
Condensed Matter - Materials Science
Abstract

The symmetry was examined using neutron diffraction method on Pb(Zn1/3Nb2/3)O3 -9%PbTiO3 (PZN/9PT) which has a composition at the morphotropic phase boundary (MPB) between Pb(Zn1/3Nb2/3)O3 and PbTiO3. The results were compared with those of other specimens with same composition but with different prehistory. The equilibrium state of all examined specimens is not the mixture of rhombohedral and tetragonal phases of the end members but exists in a new polarization rotation line Mc# (orthorhombic-monoclinic line). Among examined specimens, one exhibited tetragonal symmetry at room temperature but recovered monoclinic phase after a cooling and heating cycle.

Published
2001
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4. Symmetry of high-piezoelectric Pb-based complex perovskites at the morphotropic phase boundary II. Theoretical treatment

Author

Yamada, Yasusada, Uesu, Yoshiaki, Matsuda, Masaaki, Fujishiro, Kouji, Cox, Dave E., Noheda, Beatriz, and Shirane, Gen

Subjects
Condensed Matter - Materials Science
Abstract

The structural characteristics of the perovskite- based ferroelectric Pb(Zn1/3Nb2/3)O3-9%PbTiO3 at the morphotropic phase boundary (MPB) region (x≃0.09) have been analyzed. The analysis is based on the symmetry adapted free energy functions under the assumption that the total polarization and the unit cell volume are conserved during the transformations between various morphotropic phases. Overall features of the relationships between the observed lattice constants at various conditions have been consistently explained. The origin of the anomalous physical properties at MPB is discussed.

Published
2001
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7. A New Aspect of the Charged Domain Wall in Hexagonal RMnO3 Systems (R: Y, In).

Author

Mori, Shigeo, Ishizuka, Hiroaki, Cheong, Sang-Wook, Nagaosa, Naoto, and Yamada, Yasusada

Abstract

We investigate the profiles of the polarization in the simple "flat" charged domain wall, specified by "head to head" ("tail to tail") configuration, in the hexagonal RMnO3 systems (R: Y and In). Detailed observations of profiles of the displacements of Y-ions (In-ions) across the above-specified domain walls have been carried out utilizing the HAADF-STEM method with the resolution as high as 20 picometers. The results show qualitatively different features from the conventionally accepted tanh(x) type polarization profile in the domain wall. Taking into account that the non-polar state exists as a (meta)stable one in addition to the two degenerate polar states, the analysis of the obtained experimental results has been carried out based on one-dimensional ϕ6 field theory. The theoretical results have shown satisfactory consistencies with experimental observations. We also recognize that the present problem may be discussed in the framework of "interacting (either attractive or repulsive) soliton pair". In this context, YMnO3 corresponds to the case where the attractive interaction dominates, resulting in merging of the solitons while InMnO3 to the case where the repulsive interaction dominates, resulting in the completely separated configuration of the two solitons. These pictures provide a new perspective to understand the "charged" domain wall in the materials under consideration. [ABSTRACT FROM AUTHOR]

Published
2019
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9. 国富研究室(理学部,<特集>大阪大学)

Author

Yamada, Yasusada, ヤマダ, ヤスサダ, 山田, 安定, Yamada, Yasusada, ヤマダ, ヤスサダ, and 山田, 安定

Abstract

この論文は国立情報学研究所の電子図書館事業により電子化されました。

Published
2009

21. Relaxor as heterophase fluctuation

Author

Yamada, Yasusada, primary, Iwase, Takeshi, additional, Fujishiro, Kouji, additional, Uesu, Yoshiaki, additional, Yamashita, Yohachi, additional, Tomeno, Izumi, additional, and Shimanuki, Senji, additional

Published
2000
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