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Investigation of Lattice Effects in Perovskites by $O-isotope^{18}$ Exchange
Itoh, Mitsuru,Mahesh, Rajappan,Wang, Ruiping The Korean Ceramic Society 2000 The Korean journal of ceramics Vol.6 No.3
In the present study, preliminary experimental results of the change in the properties of perovskite-type oxides caused by the $^{18}O$- exchange have been reported. Two systems were selected for the exchange, (1) $ATiO_3$(A=Ca,Sr,Ba) and (2) manganese perovskite. The dielectric properties of isotope-exchanged $SrTi^{18}O_3$showed a drastic change from a quantum paraelectricity below 3K to ferroelectric-like behavior with a peak at 23K and an enhanced dielectric constant, 35000 at the peak. On the contrary, the $T_c$ for $BaTiO_3$was found to increase by 0.9K. The observed isotope shift of $T_c$ as well as $T_co$ for the manganese perovskites is correlated with the key parameters controlling the lattice such as $Mn^{3+}$ content, average ionic radius of the A-site cation <$r_A$> ad A-site ionic disorder $\sigma^2$.
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
Effects of Electric Field on Raman Spectra in SrTi16O3 and SrTi18O3
Kohji Abe,Mitsuru Itoh,Osamu Sanaka,Ruiping Wang,Takashi Akaike,Takeshi Shigenari,Tomohiko Takemoto 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Proton ordering phase transition of ice crystal was studied by Raman pectroscopy. The difference of the vibrational modes between Ih and XI phase were detected for the rst time in the translation region and in the libration region. Below Tc(= 72K), in the translation region a new intense peak was observed at 236 cm1 and the peak at 315 cm1 in Ih phase shifted to 325 cm1. In the libration region several new peaks were observed. Assignments of these modes are discussed from the polarization dependence.
Hiroki Taniguchi,Masaki Takesada,Mitsuru Itoh,Toshirou Yagi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
The oxygen-isotope exchange eect on the ferroelectric micro-regions (FMR) in SrTiO3 is investigated by Raman scattering in the low-temperature region near 1 K by using a 3He cryostat. With decreasing temperature, the intensity of the FMR spectra decreases and a sharp peak newly appears with increasing intensity. The sharp peak is assigned to be the polar Eu mode activated by local symmetry breaking induced by the growth of FMR.
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.
Hiroshi Takashima,조명희,Tomoyasu Taniyama,Mitsuru Itoh 한국물리학회 2017 Current Applied Physics Vol.17 No.5
Epitaxial SrTiO3 thin film was grown on 1%-Nb-doped SrTiO3 (001) substrate by pulsed laser deposition (PLD). Post-annealing at 1050 C drastically changes the particle-type surface morphology of the asgrown film to a well-defined step-terrace structure. An atomically smooth surface was obtained with a step height of about 0.4 nm, which corresponds to one-unit-cell of SrTiO3 (a ¼ 0.3905 nm). The dielectric constants εr at 300 and 2 K were found to be 120 and 520 at 100 kHz, respectively. The dielectric losses at 300 and 2 K were 2.0 105 and 1.2 105 at 100 kHz, respectively. Temperature dependence of the dielectric properties showed suppressed quantum paraelectricity. Post-annealed films with an atomically smooth surface used as an insulating layer contribute to the high performance of thinfilm electroluminescent (TFEL) heterostructure devices. Preparation of ideal interfaces of different materials may aid in the development of heterostructure electronic devices.
Strong anisotropy of ferroelectricity in lead-free bismuth silicate.
Seol, Daehee,Taniguchi, Hiroki,Hwang, Jae-Yeol,Itoh, Mitsuru,Shin, Hyunjung,Kim, Sung Wng,Kim, Yunseok RSC Pub 2015 Nanoscale Vol.7 No.27
<P>Bismuth silicate (Bi2SiO5) was recently suggested as a potential silicate based lead-free ferroelectric material. Here, we show the existence of ferroelectricity and explore the strong anisotropy of local ferroelectricity using piezoresponse force microscopy (PFM). Domain structures are reconstructed using angle-resolved PFM. Furthermore, piezoresponse hysteresis loops and piezoelectric coefficients are spatially investigated at the nanoscale. The obtained results confirm the existence of ferroelectricity with strong c-axis polarization. These results could provide basic information on the anisotropic ferroelectricity in Bi2SiO5 and furthermore suggest its considerable potential for lead-free ferroelectric applications with silicon technologies.</P>
Thermal, Dielectric, and Magnetic Properties in Multiferroic Cu2.85Zn0.15Mo2O9
Haruhiko Kuroe,Kento Aoki,Ryusuke Itoh,Tomohiro Hosaka,Takuya Hasegawa,Suguru Hachiuma,Mitsuru Akaki,Hideki Kuwahara,Tomoyuki Sekine,Masashi Hase,Kunihiko Oka,Toshimitsu Ito,Hiroshi Eisaki 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We study the effects of Zn substitution on single crystals of the low-dimensional multiferroicmaterial Cu3Mo2O9. We report the magnetic field-temperature phase diagram obtained from thetemperature and the magnetic field dependences of the specific heat, the dielectric constant, thedifferential magnetization, and the electric polarization-electric field curve in Cu2.85Zn0.15Mo2O9. We obtain three phases: a paraelectric and a ferroelectric phase, and a ferroelectric phase with alarge coercive electric field. The origin of the last one is discussed based on the charge redistributioneffect on a half-filled Mott insulator. In this phase, the Zn substitution induces a robust localizedferroelectric polarization that increases the coercive electric field.