Yoneda, Yasuhiro; Taniguchi, Hiroki*; Kitanaka, Yuki*; Noguchi, Yuji*
Ferroelectrics, 538(1), p.57 - 62, 2019/05
High-energy X-ray diffraction study was performed on lead titanate (PbTiO). Short-range order structure was revealed using atomic pair-distribution function (PDF) method. In the high-temperature cubic phase, there is a large deviation between local and average structure. Especially, Pb atoms deviated from the cubic lattice framework, but establish Pb-O-Pb random network.
Yoneda, Yasuhiro; Taniguchi, Hiroki*; Fu, D.*
Ferroelectrics, 513(1), p.1 - 6, 2017/09
An EXAFS study of lead magnesium niobate was performed at the Nb K edge and at the Pb L3 edge at 300 K. Two Nb-O bond lengths of 1.91 and 2.10 are observed and there is no significant modification of the local environment of the Nb atoms compared with NaNbO and AgNbO. The weak Pb L3 EXAFS signal indicated a strong static disorder, which can be extracted by PDF analysis.
Kim, J.*; Yamanaka, Satoru*; Nakajima, Akira*; Kato, Takanori*; Kim, Y.*; Fukuda, Tatsuo; Yoshii, Kenji; Nishihata, Yasuo; Baba, Masaaki*; Takeda, Masatoshi*; et al.
Ferroelectrics, 512(1), p.92 - 99, 2017/08
Yoneda, Yasuhiro; Kohara, Shinji*
Ferroelectrics, 485(1), p.34 - 41, 2015/00
High-energy X-ray total scattering provides simultaneous information about long-range order through the Bragg peaks and short-range order through the diffuse scattering. In ferroelectric materials, short-range order structure inside the ferroelectric domains tends to deviate from the average structure. The local structure analysis is necessary to reveal the ferroelectric mechanism. We applied atomic pair-distribution function (PDF) analysis using synchrotron X-ray for the study of local structure of ferroelectrics having perovskite structure. In BaTiO, since local distortion is averaged out owing to the requirements of periodicity and harmonic lattice vibrations, the average structure showed a cubic structure. The actual structure of systems which displays so much instability and disorder can be revealed by the PDF analysis.
Oishi, Daisuke*; Hayakawa, Hironori*; Akahama, Hiroshi*; Ikeda, Naoshi*; Kambe, Takashi*; Matsuo, Yoji*; Kimizuka, Noboru*; Kano, Jun*; Yoshii, Kenji
Ferroelectrics, 415(1), p.51 - 56, 2011/10
The variation of AC dielectric constant in the function of the DC magnetic fields was found in low oxygen vacant LuFeO single crystal in which the electric polarization arise from the polar charge ordering. These magneto-electric coupling should be explained by a novel mechanism where the boundary motion of the polar charge ordered domain is affected by the magnetic (spin) domain boundary motion.
Ferroelectrics, 414(1), p.86 - 89, 2011/06
The numerical model of the ferroelectric domain formation has been described with the polarization network, because it has been understood that a long-range network of elastic strain is generated by the inhomogeneity of polarization. Recently, the direct observation of long-range elastic strain has been able to be performed by several methods. We made an attempt to construct a mathematical model of the domain formation in BaTiO using elastic strain as a parameter.
Matsuo, Yoji*; Hirata, Akihiko*; Horibe, Yoichi*; Yoshii, Kenji; Ikeda, Naoshi*; Mori, Shigeo*
Ferroelectrics, 380(1), p.56 - 62, 2009/06
Diluted effect on the charge ordered (CO) structure in dielectric materials LuFeO (=Cu, Co) were investigated by an energy-filtered transmission electron microscope (TEM), in combination with a conventional TEM. It is revealed that partial substitution of Cu and Co for Fe in LuFeO destabilized the CO structure. In LuFeCuO, there exist characteristic zigzag-shaped diffuse streaks and diffuse spots at the h/3- h/3- 0-type positions (h: integer, =0.06) in reciprocal space, which originate from static cationic ordering of Fe and Cu ions in the triangular lattice. Moreover, real-space images by the energy-filtered TEM revealed that nanometer-sized domain structures with the 510 nm size are formed. In contrast, honeycomb-shaped diffuse streaks were found in LuFeCoO, in which no domain structures are observed in real-space images.
Yoshii, Kenji; Hiramitsu, Yusuke*; Yoneda, Yasuhiro; Okajima, Yuka; Nishihata, Yasuo; Mizuki, Junichiro; Ikeda, Naoshi*
Ferroelectrics, 379(1), p.183 - 190, 2009/05
The magnetic and dielectric properties of perovskite manganites RCaMnO (R=Eu-Lu) have been investigated. Their dielectric constants were about 1000 at around room temperature. Inflections or peaks of temperature dependences of the dielectric constants were observed at around the charge-ordering temperatures determined from the magnetic measurements. Analyses of tan and EXAFS spectra suggested that the dielectric properties of this system are due to a spatial arrangement and transfer of the Mn-3d electrons. The observation of a two-peak structure of tan indicates that dielectric measurement can be used to observe homogeneity or in homogeneity of sample, as mentioned in our previous paper.
Michiuchi, Takamasa*; Yokota, Yusuke*; Komatsu, Takuma*; Hayakawa, Hironori*; Kuroda, Tomoko*; Maeda, Daisuke*; Matsuo, Yoji*; Mori, Shigeo*; Yoshii, Kenji; Hanasaki, Noriaki*; et al.
Ferroelectrics, 378(1), p.175 - 180, 2009/00
We have synthesized the samples of LuFeO, which shows the ferroelectricity due to charge ordering of Fe ions, under several different reducing conditions using a CO-CO flow. The reducing condition was changed by changing a flow ratio of CO and CO. It was found that the flow ratio of CO/CO of about 5 provided the sample with the highest magnetic transition temperature of 240-250 K. This sample showed the dielectric constant of 10000 at room temperature. The imaginary part of the dielectric response offered the activation energy of 0.4-0.5 eV, which is slightly larger than that reported previously (about 0.3 eV). We will perform further investigation of the physical properties of this sample to clarify full details and their origin of LuFeO.
Yoneda, Yasuhiro; Mizuki, Junichiro; Takeda, Hiroaki*; Shiosaki, Tadashi*
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 55(5), p.971 - 974, 2008/05
We performed synchrotron X-ray topography on a LaTaGaO (LTG) crystal grown by the Czochralski (Cz) method. Since the synchrotron X-ray source can provide high-energy X-rays, one can detect bulk-sensitive information by the X-ray topography. LTG is one of the most attractive piezoelectric crystals like LaGaSiO (LGS), because of excellent acoustic properties (temperature compensation of acoustic losses). Since LTG single crystals can be grown from stoichiometric melt, single crystals with good crystal quality can be obtained comparing to LGS which can not be grown from stoichiometric system but from congruent melt. The 60-keV X-ray topography revealed that the LTG crystal quality was not the same crystalline quality. The crystal quality of a center parts was worse than that of surroundings.
Ikeda, Naoshi*; Matsuo, Yoji*; Mori, Shigeo*; Yoshii, Kenji
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 55(5), p.1043 - 1045, 2008/05
We report our recent discovery of novel ferroelectricity arising from the polar ordering of Fe and Fe in a mixed valence triangular lattice oxide LuFeO, where the electric polarization is not a result of ionic displacement. The polar ordering of Fe and Fe was confirmed with a resonant X-ray scattering study in SPring-8. The origin of such ordering is the competitive interaction between Fe and Fe in the triangular lattice, i.e., the charge frustration. The polar superlattice of Fe and Fe develops below 350 K, where the electric polarization appears. The ferroelectricity arising from the polar charge ordering or the polar electron distribution may have great potential for the future application of ferroelectrics.
Kitagawa, Shuji*; Ozaki, Tomoatsu*; Horibe, Yoichi*; Yoshii, Kenji; Mori, Shigeo*
Ferroelectrics, 376(1), p.122 - 128, 2008/00
Microstructures associated with the ferroelectric (FE) properties in (1-x)BiFeO-xBaTiO were investigated mainly by a transmission electron microscopy. It was found that large FE domains in BiFeO changed into complicated FE microdomains with the 20-30 nm width in the x = 0.25 compound. The directions of the spontaneous polarization in each FE microdomains were determined by obtaining dark-field images. Changes of the FE microdomains for x = 0.28 composition as a function of the temperature were also investigated.
Yoneda, Yasuhiro; Yoshii, Kenji; Saito, Hiroyuki; Mizuki, Junichiro
Ferroelectrics, 348, p.33 - 37, 2007/03
no abstracts in English
Kimura, Hiroyuki*; Kobayashi, Satoru*; Wakimoto, Shuichi; Noda, Yukio*; Kon, Keiichiro*
Ferroelectrics, 354, p.77 - 85, 2007/01
A review is given on the studies of magnetic properties and dielectric properties as functions of temperature and magnetic field for various multiferroic MnO ( = rare-earth) compounds. We have observed successive dielectric and magnetic phase transitions which concomitantly take place and a so-called multiferroics is realized. In this system, the ferroelectricity is magnetically induced and the commensurate magnetism is indispensable to produce a spontaneous electric polarization. The microscopic origin of the magnetically induced ferroelectricity and the role of the rare-earth magnetic moment for a colossal magnetoelectric effect in MnO will be discussed in the viewpoint of the magnetic structure.
Yoneda, Yasuhiro; Matsumoto, Norimasa; Suzuya, Kentaro; Kohara, Shinji*; Mizuki, Junichiro
Ferroelectrics, 268, p.277 - 282, 2002/00
no abstracts in English
Egusa, Shigenori; *
Ferroelectrics, 145, p.45 - 60, 1993/00
no abstracts in English
Ferroelectrics, 96, p.195 - 198, 1989/00
no abstracts in English