JOPSS - Search Results

Journal Articles

PSTEP: Project for solar-terrestrial environment prediction

Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.

Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12

https://doi.org/10.1186/s40623-021-01486-1

Times Cited Count：6 Percentile：51.19(Geosciences, Multidisciplinary)

The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

Journal Articles

Local structure modulation in the electronic ferroelectric oxide LuFe $_{2}$ O $_{4}$

Hayakawa, Hironori*; Morimoto, Masanori*; Ikeda, Naoshi*; Yoneda, Yasuhiro; Kohara, Shinji*; Yoshii, Kenji; Matsuo, Yoji*; Michiuchi, Takamasa*; Mori, Shigeo*

Transactions of the Materials Research Society of Japan, 34(1), p.51 - 54, 2009/05

https://doi.org/10.14723/tmrsj.34.51

We have recently reported that LuFe $_{2}$ O $_{4}$ becomes ferroelectric below 330 K, owing to a charge-ordering transition of Fe ions. As details of the properties of this material have not been reported so far, we have investigated its local structure in the ferromagnetic phase by means of synchrotron X-ray diffraction. The analysis of pair-distribution function showed the existence of displacement of Lu atoms; this structure is different from the average structure of this materials known thus far. This result encourages a detailed reinvestigation of crystal structure of LuFe $_{2}$ O $_{4}$ . We also show the results obtained from some other experimental methods, such as dielectric measurement and electron diffraction.

Journal Articles

Stoichiometric study of the dielectric and magnetic properties in charge frustrated system LuFe $_{2}$ O $_{4}$

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

https://doi.org/10.1080/00150190902859187

Times Cited Count：18 Percentile：59.66(Materials Science, Multidisciplinary)

We have synthesized the samples of LuFe $_{2}$ O $_{4}$ , which shows the ferroelectricity due to charge ordering of Fe ions, under several different reducing conditions using a CO $_{2}$ -CO flow. The reducing condition was changed by changing a flow ratio of CO $_{2}$ and CO. It was found that the flow ratio of CO $_{2}$ /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 LuFe $_{2}$ O $_{4}$ .

Journal Articles

Evidence for a difference in the dissociation mechanisms of acetylene (HCCH) and vinylidene (H $_{2}$ C=C:) from charge inversion mass spectrometry

Hayakawa, Shigeo*; Tomozawa, Koji*; takeuchi, takae*; Arakawa, Kazuo; Morishita, Norio

Physical Chemistry Chemical Physics, 5(11), p.2386 - 2390, 2003/05

https://doi.org/10.1039/B212834A

Times Cited Count：15 Percentile：44.45(Chemistry, Physical)

The process of formation of the negative ions in charge inversion mass spectrometry is via near-resonant neutralization followed by spontaneous dissociation, and then endothermic negative ion formation. The intensity of the C $_{2}$ $^{-}$ peak relative to the C $_{2}$ H $^{-}$ peak in these spectra increased with decreasing ionization potential of the targets for both of the isomeric C $_{2}$ H $_{2}$ $^{+}$ cations. The formation of the C $_{2}$ $^{-}$ anion is proposed to result from the dissociation of excited C $_{2}$ H $_{2}$ neutrals into C $_{2}$ and H $_{2}$ . The dependence on target species of the intensities of C $_{2}$ $^{-}$ peak relative to the C $_{2}$ H $^{-}$ peak for HCCH and H $_{2}$ C=C: cannot be rationalized by the internal energy of the excited C $_{2}$ H $_{2}$ neutrals. The differences indicate that the isomeric C $_{2}$ H $_{2}$ neutrals dissociate into C $_{2}$ H and H prior to 1,2-hydrogen atom migration.

Journal Articles

A New technique to study the dissociation of energy-selected neutral intermediates

Hayakawa, Shigeo*; Harada, Kengo*; Watanabe, Nobuaki*; Arakawa, Kazuo; Morishita, Norio

International Journal of Mass Spectrometry, 202(1-3), p.A1 - A7, 2000/10

https://doi.org/10.1016/S1387-3806(00)00286-4

Times Cited Count：16 Percentile：60.07(Physics, Atomic, Molecular & Chemical)

no abstracts in English

Journal Articles

Study of dissociation of neutral intermediates using charge inversion mass spectrometry

Hayakawa, Shigeo*; Harada, Kengo*; Arakawa, Kazuo; Morishita, Norio

Journal of Chemical Physics, 112(19), p.8432 - 8435, 2000/05

https://doi.org/10.1063/1.481446

Times Cited Count：19 Percentile：50.82(Chemistry, Physical)

no abstracts in English

Journal Articles

Definitive evidence for the existence of a long-lived vinylidene radical cation, H $_{2}$ C=C $^{+}$

Hayakawa, Shigeo*; *; Arakawa, Kazuo; Morishita, Norio

Journal of Chemical Physics, 110(6-8), p.2745 - 2748, 1999/02

https://doi.org/10.1063/1.477875

Times Cited Count：21 Percentile：55.28(Chemistry, Physical)

no abstracts in English

Journal Articles

Dissociation mechanism of electronically excited C $_{3}$ H $_{4}$ isomers by charge inversion mass spectrometry

Hayakawa, Shigeo*; *; Arakawa, Kazuo; Morishita, Norio

Int. J. Mass Spectrom. Ion Process, 171(1-3), p.209 - 214, 1997/00

no abstracts in English

Oral presentation

Dielectric properties on charge ordered ferroelectrics LuFe $_{2}$ O $_{4}$

Ikeda, Naoshi*; Kambe, Takashi*; Komatsu, Takuma*; Michiuchi, Takamasa*; Hayakawa, Hironori*; Hanasaki, Noriaki*; Yoshii, Kenji; Matsuo, Yoji*; Mori, Shigeo*

no journal, ,

A review will be given on the new type of ferroelectric material LuFe $_{2}$ O $_{4}$ . This oxide becomes ferroelectric below about 330 K, owing to the charge-ordered arrangement of Fe ions on a triangular lattice: This is a novel mechanism of ferroelectricity. We discuss the experimental results obtained from resonant X-ray diffraction, dielectric response, polarization and magnetization to show some interesting properties of this new ferroelectric oxide.

Oral presentation

Local structure of triangular-lattice oxides LuFeMO $_{4}$ (M=Co,Cu)

Matsuo, Yoji*; Mori, Shigeo*; Yoshii, Kenji; Hayakawa, Hironori*; Ikeda, Naoshi*

no journal, ,

We have investigated the local structure of LuFe(Co,Cu)O $_{4}$ , in which half of Fe ions are replaced by Co and Cu in electronic ferroelectric LuFe $_{2}$ O $_{4}$ . It was found that the electron diffraction patterns at room temperature showed diffuse scattering besides fundamental spots. Based on calculations for possible model structures, we suggest the existence of 4-point clusters consisting of Fe and Co/Cu, which is likely the origin of dielectric constant of 10-1000 at room temperature.

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PSTEP: Project for solar-terrestrial environment prediction

Local structure modulation in the electronic ferroelectric oxide LuFe $_{2}$ O $_{4}$

Stoichiometric study of the dielectric and magnetic properties in charge frustrated system LuFe $_{2}$ O $_{4}$

Evidence for a difference in the dissociation mechanisms of acetylene (HCCH) and vinylidene (H $_{2}$ C=C:) from charge inversion mass spectrometry

A New technique to study the dissociation of energy-selected neutral intermediates

Study of dissociation of neutral intermediates using charge inversion mass spectrometry

Definitive evidence for the existence of a long-lived vinylidene radical cation, H $_{2}$ C=C $^{+}$

Dissociation mechanism of electronically excited C $_{3}$ H $_{4}$ isomers by charge inversion mass spectrometry

Dielectric properties on charge ordered ferroelectrics LuFe $_{2}$ O $_{4}$

Local structure of triangular-lattice oxides LuFeMO $_{4}$ (M=Co,Cu)