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Journal Articles

Ginzburg-Landau action and polarization current in an excitonic insulator model of electronic ferroelectricity

Adachi, Hiroto*; Ikeda, Naoshi*; Saito, Eiji

Physical Review B, 107(15), p.155142_1 - 155142_10, 2023/04

https://doi.org/10.1103/PhysRevB.107.155142
 Times Cited Count：2 Percentile：75.57(Materials Science, Multidisciplinary)

Journal Articles

Elemental substitution effects in multiferroic ${it R}$Fe$$_{2}$$O$$_{4}$$ (${it R}$: rare earths)

Yoshii, Kenji; Funae, Takeshi*; Mizumaki, Masaichiro*; Ejiri, Hiroki*; Ikeda, Naoshi*; Saito, Hiroyuki; Matsumura, Daiju

Physica Status Solidi (C), 12(6), p.841 - 844, 2015/06

https://doi.org/10.1002/pssc.201400250
 Times Cited Count：1 Percentile：40.68(Physics, Condensed Matter)

We report the effects of elemental substitutions in multiferroic ${it R}$Fe$$_{2}$$O$$_{4}$$ ($$R$$: Y, Ho-Lu, In). The substitution by nonmagnetic Ga$$^{3+}$$ at the Fe site, which has not been reported so far, shows a drastic decrease in the ferrimagnetic transition temperature ($$T_{rm N}$$). This is plausibly owing to the suppression of magnetic interactions between Fe ions, based on our previous results of other substituted systems such as ${it R}$FeCoO$$_{4}$$. Dielectric constants near room temperature were comparable to those of $$R$$Fe$$_{2}$$O$$_{4}$$. The suppression of dielectric loss in this system is suitable to application. The ${it R}$-site substitution was also attempted by the large R$$^{3+}$$ ions such as Dy$$^{3+}$$. The solubility limit was up to about 10% of ${it R}$ ions, as confirmed by XRD and EXAFS measurements. $$T_{rm N}$$ was raised by 5-10 K for Dy$$^{3+}$$ substitution.

Journal Articles

Current-induced enhancement of magnetic anisotropy in spin-charge-coupled multiferroic YbFe$$_{2}$$O$$_{4}$$

Yoshii, Kenji; Matsumura, Daiju; Saito, Hiroyuki; Kambe, Takashi*; Fukunaga, Mamoru*; Muraoka, Yuji*; Ikeda, Naoshi*; Mori, Shigeo*

Journal of the Physical Society of Japan, 83(6), p.063708_1 - 063708_4, 2014/06

https://doi.org/10.7566/JPSJ.83.063708
 Times Cited Count：4 Percentile：34.67(Physics, Multidisciplinary)

We report the change of magnetic properties of multiferroic YbFe$$_{2}$$O$$_{4}$$, caused by cooling in the presence of an electrical current. The magnetization measured after the cooling becomes smaller by about 10-20% than that after cooling without a current. The current also affects the magnetic anisotropy below about 100 K; the magnetic coercivity is increased by about 10-20%. These phenomena may arise from a coexistence of ferromagnetic and antiferromagnetic domains, or a disturbance in the formation of charge-ordered domains. From the applied viewpoint, the enhancement of anisotropy by an electrical current offers a method for stabilizing magnetization other than the well-known method, i.e., exchange bias.

Journal Articles

Magnetic properties of single crystalline YbFe$$_{2}$$O$$_{4}$$

Yoshii, Kenji; Mizumaki, Masaichiro*; Matsumoto, Keisuke*; Mori, Shigeo*; Endo, Naruki; Saito, Hiroyuki; Matsumura, Daiju; Kambe, Takashi*; Ikeda, Naoshi*

Journal of Physics; Conference Series, 428, p.012032_1 - 012032_5, 2013/04

https://doi.org/10.1088/1742-6596/428/1/012032
 Times Cited Count：14 Percentile：96.93(Chemistry, Applied)

We have investigated a single crystal of multiferroic YbFe$$_{2}$$O$$_{4}$$. Its magnetic transition temperature was 250 K. The magnetization along the c-axis was much larger than that within the ab plane, indicating the Ising character of this system. The field-cooled magnetization became negative below 10 K. This was explained in terms of an antiparallel coupling between Yb and Fe moments. Magnetocaloric effects were also observed. The change of entropy was found to show a broad peak with a width of 100 K, which is favorable to application.

Journal Articles

High pressure and temperature synthesis of Bi-based perovskite Bi$$_{0.5}$$Na$$_{0.5-x}$$Li$$_x$$)TiO$$_3$$

Fukunaga, Masanori; Yoneda, Yasuhiro; Fukuyama, Ryota*; Saito, Hiroyuki; Ikeda, Naoshi*; Katayama, Yoshinori

Transactions of the Materials Research Society of Japan, 35(1), p.111 - 114, 2010/03

https://doi.org/10.14723/tmrsj.35.111

High-pressure synthesis of bismuth based perovskite (Bi$$_{0.5}$$Na$$_{0.5-x}$$Li$$_x$$)TiO$$_3$$ (BNLT) ($$x$$=0.1, 0.15, 0.2, 0.25, 0.4, 0.5) was demonstrated. Single phase BNLTs with perovskite structure were successfully synthesized for $$x$$$$leq$$0.1 by the solid state reaction method. The solid phase reaction occurred in the pressure range of 6-10 GPa, and in the temperature range of 800-1200 $$^{circ}$$C. Two thermal anomalies were observed in single phase perovskite BNLT ($$x$$=0.1) as well as (Bi,Na)TiO$$_3$$. The cusp like anomaly at 210 $$^{circ}$$C was assigned to a rhombohedral-tetragonal structural phase transition. The finished products of $$x$$$$geq$$0.2 included three kinds of impurities, which were affected by the selection of starting materials.

Journal Articles

Growth and characterization of bismuth magnesium titanate Bi(Mg$$_{1/2}$$Ti$$_{1/2}$$)0$$_3$$

Yoneda, Yasuhiro; Saito, Hiroyuki; Yoshii, Kenji; Nishida, Takashi*; Hayakawa, Hironori*; Ikeda, Naoshi*

Key Engineering Materials, 421-422, p.30 - 33, 2010/00

Polycrystalline Bi(Mg$$_{1/2}$$Ti$$_{1/2}$$)O$$_3$$ samples were prepared under high pressure. A mixed powder of Bi$$_2$$O$$_3$$, Ti$$_2$$O$$_3$$ and MgO with a prescribed ratio was packed into platinum cell and was heated a cubic anvil-type apparatus at 6.5 GPa and 1000 $$^circ$$C. The obtained samples were characterized by powder X-ray diffraction measurements. Although some impurity peaks existed, the main peaks were perovskite peaks. The structure of Bi(Mg$$_{1/2}$$Ti$$_{1/2}$$)O$$_3$$ is rhombohedral, as well as BiFeO$$_3$$. The D-E hysteresis loop was not saturated due to the impurities, but the possibility as ferroelectric can be expected enough.

JAEA Reports

Study on sodium combustion behavior (III); NRIFD/JNC Joint Research Project

Saito, Naoshi*; Tsuruda, Takashi*; Wada, Yusaku

JNC TY9200 2004-002, 61 Pages, 2003/03

JNC-TY9200-2004-002.pdf:2.95MB

On the research related to combustion behavior in coolant sodium leak in the fast reactor, it is important to phenomenologically clarify the behavior in addition to conventional engineering challenge. National Research Institute of Fire and Disaster(NRIFD) and Japan Nuclear Cycle Development Institute(JNC) have done cooperative research since the 1998 fiscal year for the purpose of deepening understanding on the sodium combustion behavior by the information exchange on basic experiment and analysis of sodium combustion behavior carried out in each institute. This report coordinated results such as information exchange conference in the 2001 - 2002 fiscal year.

JAEA Reports

None

Saito, Naoshi*; Tanabe, Hiromi

JNC TY9200 99-001, 44 Pages, 1999/03

JNC-TY9200-99-001.pdf:1.96MB

None

Oral presentation

Rare earth substitution effects in multiferroic RFe$$_{2}$$O$$_{4}$$ (R: rare earths)

Yoshii, Kenji; Matsumura, Daiju; Endo, Naruki; Saito, Hiroyuki; Yoneda, Yasuhiro; Nishihata, Yasuo; Funae, Takeshi*; Ejiri, Hiroki*; Kano, Jun*; Kobayashi, Tatsuo*; et al.

no journal, , 

We have investigated the substitution effects at the rare-earth (R) site in multiferroic RFe$$_{2}$$O$$_{4}$$ (R: Y, Ho-Lu) to explore a new phase of this system. From EXAFS measurements for the R atoms, the large R$$^{3+}$$ ions (such as Dy$$^{3+}$$) was partially substituted in RFe$$_{2}$$O$$_{4}$$. Powder X-ray diffraction showed that this material had a single-phase RFe$$_{2}$$O$$_{4}$$-type structure (space group R-3m). The simulated EXAFS spectrum reproduced the characteristics of the experimental spectrum, confirming that R$$^{3+}$$ is actually settled at the rare earth site. The other results, such as the magnetic properties, will be reported at the conference.

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