- 著者
- Hira Asuka Yabe Hiromasa Yoshida Kenichi Okuno Yusuke Shiraishi Yuichi Chiba Kenichi Tanaka Hiroko Miyano Satoru Nakamura Jun Kojima Seiji Ogawa Seishi Matsuo Keitaro Takata Minoru Yabe Miharu
- 出版者
- American Society of Hematology
- 雑誌
- Blood (ISSN:00064971)
- 巻号頁・発行日
- 2013-09-13
- 被引用文献数
- 146
「アルデヒド分解酵素遺伝子」ALDH2が解き明かす難病の謎. 京都大学プレスリリース. 2013-09-13
- 著者
- Kojima Seiji Tsumura Naoki Wada Takeda Mitsuo Nishizawa Seizi
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.67, no.3, pp.035102, 2003-01
- 被引用文献数
- 52 39
We report observations of the intensity and phase transmission spectra related to phonon-polariton propagation using coherent far-infrared radiation for a high-quality ferroelectric bismuth titanate crystal plate. In order to determine the polariton-dispersion relation, the phase delay was determined minutely as a function of the THz radiation frequency in the region between 3 and 100 cm-1. The anisotropy of polariton dispersion relation was also successfully determined on the c plate simply by switching the polarization direction of an incident beam from E∥a to E∥b. The observed polariton dispersion relations are consistently reproduced by the calculation using Kurosawa’s formula.
- 著者
- Lushnikov S G Fedoseev A I Gvasaliya S N Ko J-H Kojima Seiji
- 出版者
- IOP Publishing
- 雑誌
- Journal of physics. Condensed matter (ISSN:09538984)
- 巻号頁・発行日
- vol.19, no.49, pp.496206, 2007-11
- 被引用文献数
- 7 6
The behavior of longitudinal acoustic (LA) and transverse acoustic (TA) phonons in a cubic relaxor PbMg1/3Ta2/3O3 (PMT) ferroelectric has been investigated by Brillouin light scattering. Analysis of the temperature dependences of phonon velocity in the temperature range from 50 to 870 K has revealed anomalies in the vicinity of the Burns temperature (TB≈570 K) for LA phonons and a wide frequency-dependent minimum of the velocities of LA and TA phonons in the same temperature region as the dielectric response anomaly. Using experimental data, temperature dependences of the C11 and C44 elastic constants have been calculated. The elastic constants have been found to be frequency-independent in the gigahertz range. The results obtained are discussed in the framework of modern ideas on the crystalline lattice dynamics of relaxor ferroelectrics.
- 著者
- Ohta Ryu Zushi Junta Ariizumi Takuma Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.98, no.9, pp.092909, 2011-02
- 被引用文献数
- 36
The precursor dynamics of a cubic–tetragonal ferroelectric phase transition of potassium tantalate niobate (KTa1−xNbxO3 with x = 0.32) crystals is studied by Brillouin scattering. The appearance of the central peak (CP) and marked softening of the elastic constant c11 are clearly observed above the Curie temperature, TC–T, owing to the interaction between the LA mode and local polarization fluctuations of polar nanoregions (PNRs). The relaxation time determined by the CP width clearly shows a critical slowing down above TC–T, indicating an order–disorder feature of the ferroelectric phase transition. The size of a dynamic PNR is evaluated, and it increases toward TC–T.
- 著者
- Ko Jae-Hyeon Lushnikov S. G. Kim Do Han Kojima Seiji Jun Byeong-Eog Hwang Yoon Hwae
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physic (ISSN:00218979)
- 巻号頁・発行日
- vol.104, no.10, pp.104105, 2008-11
- 被引用文献数
- 9 5
Acoustic properties were investigated for four tungsten bronze (TB) uniaxial ferroelectric crystals, i.e., (Sr0.61Ba0.39)5Nb10O30 (SBN61), Cu-doped (K0.5Na0.5)1.0(Sr0.75Ba0.25)4.5Nb10O30 (KNSBN:Cu), K5.80Li3.82Nb10.12O30, and K4.74Li3.07Nb10.44O30 of which the spontaneous polarization is directed along the polar c axis. Large acoustic anisotropy between the two elastic constants C11 and C33 have been observed from all samples. C33 exhibits a significant softening on approaching the diffuse phase transition temperature from high-temperature side while C11 does not show any substantial change in the same temperature range. This softening is accompanied by substantial growth of hypersonic damping, appearance and growth of central peak (CP), and slowing down of the relevant dynamics of CP represented by the reducing half width. All these results indicate that the lattice motions along the c axis couple strongly to the one-component order parameter of the polar nanoregions (PNRs) or precursor polar clusters which form and grow below a certain temperature in the paraelectric phase. The inverse dielectric constant measured along the c axis of SBN61 and KNSBN:Cu can be described by two linear regions divided by a crossover temperature at which the change in the magnitude of dipole moments and the strength of the dipole couplings are expected due to the formation of PNRs. C33 of SBN61 becomes continuously softened upon cooling even when the temperature crosses the Burns temperature TB at which PNRs begin to appear. It may suggest that additional relaxation process other than that of PNRs may exist at high temperatures above TB and couple to the longitudinal acoustic waves propagating along the polar axis. Recent observation of a single-particle relaxation at high temperatures and its transformation into a collective relaxation of PNRs by dielectric spectroscopy [Belous et al., J. Appl. Phys. 102, 014111 (2007)] might be related to the anomalous acoustic behavior of SBN61 observed above TB.
- 著者
- Shabbir Ghulam Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.105, no.3, pp.034106, 2009
- 被引用文献数
- 7 5
Lanthanum-doped lead zirconate titanate, PLZT-x/65/35 (x=8.0, 9.0, and 9.4), relaxor ferroelectric ceramics were investigated by the high resolution Brillouin light scattering spectroscopy in the temperature range from ~870 down to ~170 K. Broad anomalies were observed in the acoustic phonon mode velocity and related elastic stiffness coefficient showing minimum between ~320–~240 K. The deviation in the acoustic mode velocity from the high temperature linearity at the Burns temperature (TB~720 K) and presence of a broad central peak in the temperature range 200T540 K were attributed to the dynamics of polar nanoregions with randomly oriented local polarization appearing due to site and/or charge disorder at both A- and B-sites of the ABO3 perovskite lattice. The presence of a new temperature point Td (~575 K) was conclusively established in PLZT-x/65/35 relaxor ceramics.
- 著者
- Ahart Muhtar Hushur Anwar Bing Yonghong Ye Zuo-Guang Hemley Russell J. Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.94, no.14, pp.142906, 2009-04
- 被引用文献数
- 27
Brillouin spectroscopy of Pb(Sc0.5Nb0.5)O3 single crystals reveals an order-disorder ferroelectric phase transition occurs at 110 °C upon cooling. A softening of the longitudinal acoustic (LA) mode is observed that can be attributed to the coupling between polar nanoregions and acoustic modes. A critical slowing down of the central peak, a feature of order-disorder ferroelectric phase transitions, is observed near Tc. The similarity in temperature dependences of the two kinds of relaxation times determined from the central peak and LA mode suggests that the changes in the central peak arise from local polarization fluctuations in the polar nanoregions.
- 著者
- Ko Jae-Hyeon Kojima Seiji Bokov Alexei A. Ye Zuo-Guang
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.91, no.25, pp.252909, 2007-12
- 被引用文献数
- 36 25
The dynamic polar nanoregions (PNRs) which form below the Burns temperature and determine the unique properties of relaxor ferroelectrics were predicted [Tinte et al., Phys. Rev. Lett. 97, 137601 (2006)] to be pinned to the quenched chemically ordered regions (CORs) usually observed in lead-containing relaxors. In Pb[(Mg1/3Nb2/3)0.45Ti0.55]O3 crystal where CORs are known to be absent, we have found the phenomena typically related to the relaxation of dynamic PNRs, namely, the significant Brillouin quasielastic scattering, the softening of the longitudinal acoustic mode, and the deviation from the Curie-Weiss law above the Curie point. This implies that PNRs may appear in crystals without CORs.
1 0 0 0 OA Direct evidence of an order-disorder nature of ferroelectric phase transitions in K2MgWO2(PO4)2
- 著者
- Maczka Miroslaw Hanuza Jerzy Majchrowski Andrzej Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.90, no.12, pp.122903, 2007-03
- 被引用文献数
- 5
K2MgWO2(PO4)2 single crystal, related to famous optical nonlinear material KTiOPO4, was investigated by micro-Brillouin scattering with a focus on the central components of the relaxation modes. A critical slowing down has been clearly observed in the vicinity of T1=436 K while suppressed by the coupling with the order parameter. The temperature dependence of the relaxation time indicates that the former transition is the second order, while the latter is strongly first order. The obtained results show that disorder processes in the sublattice of potassium ions play a major role in the mechanism of these phase transitions.
1 0 0 0 OA Broadband inelastic light scattering of a relaxor ferroelectric 0.71Pb(Ni1/3Nb2/3)O3-0.29PbTiO3
- 著者
- Tsukada Shinya Ike Yuji Kano Jun Sekiya Tadashi Shimojo Yoshihito Wang Ruiping Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.89, no.21, pp.212903, 2006-11
- 被引用文献数
- 40 28
Brillouin and Raman scatterings of a 0.71Pb(Ni1/3Nb2/3)O3-0.29PbTiO3 single crystal have been measured to investigate broadband inelastic spectra. The two different central peaks related to fast and slow relaxation processes have been observed separately. These two processes are attributed to the thermally activated switching of polarization in polar nanoregions. By the analysis of modified superparaelectric model, the activation energies of fast and slow relaxation processes are determined to be 3.66×103 and 4.31×102 K, respectively. The fast process with the lower activation energy probably originated from 180° switching, whereas the slow one with the higher energy from non-180° switching.
- 著者
- Hushur Anwar Shigematsu Hirotake Akishige Yukikuni Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.86, no.11, pp.112903, 2005-03
- 被引用文献数
- 28 25
Ferroelectric single crystals of BaTi2O5 have been studied in detail by Raman and high-resolution micro-Brillouin scattering with a focus on the central component of the relaxation mode over a wide temperature range (20–600 °C). A relaxation mode has been clearly observed in these single crystals. The temperature dependences of the relaxation time and integrated intensity of the relaxation mode are well reproduced by the extended semiclassical tunneling model. The ferroelectric phase transition shows, at least near the vicinity of Tc, an order-disorder nature. Our results indicate that the spontaneous polarization mainly resulted from the dynamic disorder of the Ti ions in the octahedra along the polar b axis of BaTi2O5.
- 著者
- Shabbir Ghulam Ko Jae-Hyeon Kojima Seiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.86, no.1, pp.012908, 2004-12
- 被引用文献数
- 11 10
High-resolution Brillouin scattering experiments have been performed to investigate the low temperature "aging" effect in lanthanum lead zirconate titanate (PLZT) relaxor ferroelectric ceramics. From the temperature dependence of the frequency shift of longitudinal acoustic mode, an acoustic anomaly was observed at T0~46 K in these ceramics with clear "aging" effect below T0. The results have been discussed in the light of stepwise freezing of the related degrees of freedom causing transition from proper to improper dipole glassy states at T0.