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Broad Doublet Spectra Observed in Strontium Titanate
Yuhji Tsujimi,Mitsuru Itoh 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
The 90± light scattering experiment has been performed in SrTi16O and SrTi(18O0:99 16O0:01)3 (STO18-99) single crystals. The frequency shift and line width of the broad doublet (BD) and those of a transverse acoustic mode are precisely measured. The physical origin of the BD is discussed together with the softening behavior of the transverse acoustic mode of STO18-99.2
Low-frequency Optical Phonons in SrTiO<sub>3</sub> under Uniaxial Stress
Yuhji Tsujimi,Tomori Yanagisawa,Toru Mogami 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.7
The transition from the quantum paraelectric state to the quantum ferroelectric state is well known to be caused by applying a uniaxial stress along the [010]<sub>c</sub> direction in SrTiO<sub>3</sub>. In order to clarify the dynamical mechanism of the transition, we have performed a 180˚ light-scattering experiment under stress at three temperatures of <i>T</i> = 5.0, 10.3, and 16.5 K in the frequency region from 1,000 GHz down to ∼ 60 GHz. We find that the ferroelectric <i>B<sub>3u</sub></i>(<i>x</i>) soft mode, which originates from the polar <i>E<sub>u</sub></i>(<i>x, y</i>) mode of a Slater type, does not soften completely, not even at the critical stress σ<sub>c</sub>. This finding indicates that some other transition mechanism, in addition to the condensation of the <i>B<sub>3u</sub></i>(<i>x</i>) mode, must be present.
Hyper-Raman scattering of SrTi18O3
Yusuke Minaki,Yuhji Tsujimi,Makoto Nakanishi,Mika Kobayashi,Mitsuru Itoh,Ruiping Wang,Toshirou Yagi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Hyper-Raman scattering experiment has been performed in the SrTi(18Ox 16O1..x)3 single crystal plate with x = 0:87. Raman inactive ferroelectric Eu Slater mode is directly detected in the tetragonal phase. The mode clearly shows a softening behavior and seems to cause the ferroelectric transition at Tc = 26 1 K.
Broad Doublet Spectra in SrTiO3
Mingqiu Tan,Yuhji Tsujimi,Toshirou Yagi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Broad doublet (BD) spectra have been investigated in quantum paraelectric SrTiO3 by a 180 Brillouin-scattering experiment. Spectral analyses suggest that the second-sound scenario seems to be unfavorable for explaining the physical origin of BD. We nd that the integrated intensity of BD shows quite strong anisotropy; the BD exists clearly around 27 K in the direction = 0.4deviated from [001]c to [110]c, whereas the BD is almost absent in the direction = 21. We also nd that the integrated intensity of the longitudinal acoustic mode decreases as increases, while that of the pure transverse acoustic mode increases. All these anisotropies can be explained by the conventional formula with Pockel's tensor, signifying that the concept of antiphase-domain walls is not needed for such explanation.
Anisotropic Nature of the Broad Doublet Spectra in SrTiO_3
Kohsuke Satoh,Yuhji Tsujimi 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.31
The 180˚ Brillouin scattering experiment has been performed to study the anisotropy of the mean free path of a broad doublet appearing in a quantum paraelectric state of SrTiO_3 (below about 40 K). The anisotropy is found to be expressed by an ellipse on the (1 1 0)_c plane; the major axis is along [001]_c (∼250 nm at ∼22 K) and the minor axis is along [110]_c (∼60 nm at ∼22} K). The elliptical area corresponds to the ferroelectric region dispersing dynamically in the tetragonal paraelectric matrix and gives the length scale of the quantum paraelectric state.
Femtosecond Time-Resolved Spectroscopic Study of the Slow Dynamics
Toshirou Yagi,June Kano,Keith A. Nelson,Takeo Watanuki,Yuhji Tsujimi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
The femtosecond time-resolved spectroscopy has been applied for the study of the B2 soft mode in the phase transition of the hydrogen-bonded ferroelectric KDP. An extremely early stage of the excitation of the B2 soft mode in KDP reveals newly existence of the mechanical forming process of the soft modes over the limit of the Debye model. The method shows its high resolution on the wave vector in the study of the A1 phonon-polariton dispersion relation of LiNbO3.
Soft Modes in SrTi18O3 Studied by Light Scattering and Dielectric Measurements
Yohei Nakata,Mika Kobayashi,Mitsuru Itoh,Ruiping Wang,Toshirou Yagi,Yuhji Tsujimi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Light-scattering and dielectric easurements have been carried out, mainly in SrTi18O3, to clarify the physical origin of the two modes (Eu1 and Eu2) which were supposed to originate from a doubly degenerated ferroelectric Eu soft mode. The combined results of both measurements strongly suggest that the Eu1 and Eu2 modes correspond to the polarization uctuation parallel to the spontaneous polarization Ps (the mode of A1 symmetry) and to that perpendicular to Ps (the mode of B2 symmetry), respectively.