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Journal Articles

Magnetocaloric effect of Sr-substituted BaFeO$$_{3}$$ in the liquid nitrogen and natural gas temperature regions

Yoshii, Kenji; Hayashi, Naoaki*; Mizumaki, Masaichiro*; Takano, Mikio*

AIP Advances (Internet), 7(4), p.045117_1 - 045117_6, 2017/04

 Times Cited Count:6 Percentile:40.28(Nanoscience & Nanotechnology)

We have investigated the magnetocaloric effect (MCE) of Ba$$_{1-x}$$Sr$$_{x}$$Fe$$^{4+}$$O$$_{3}$$ (x$$underline{<}$$0.2), a series of cubic perovskites showing a field-induced transition from helical antiferromagnetism to ferromagnetism. The maximum magnetic entropy change (-$$Delta$$S$$_{max}$$) at 50 kOe varies from $$sim$$ 5.8 J kg$$^{-1}$$K$$^{-1}$$ (x=0) to $$sim$$ 4.9 J kg$$^{-1}$$K$$^{-1}$$ (x=0.2), while the refrigerant capacity remains almost the same at $$sim$$165 J kg$$^{-1}$$. Interestingly, the temperature of -$$Delta$$S$$_{max}$$ decreases from $$sim$$116 K to $$sim$$77 K with increasing x, providing this series of rare-earth-free oxides with potential as a magnetic refrigerant for the liquefaction of nitrogen and natural gas.

Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Report of ITPA TG Meetings, 52

Shinohara, Koji; Hayashi, Nobuhiko; Isayama, Akihiko; Miyato, Naoaki; Urano, Hajime; Aiba, Nobuyuki

Purazuma, Kaku Yugo Gakkai-Shi, 91(12), p.797 - 800, 2015/12

no abstracts in English

Journal Articles

Effects of toroidal rotation shear and magnetic shear on thermal and particle transport in plasmas with electron cyclotron heating on JT-60U

Yoshida, Maiko; Honda, Mitsuru; Narita, Emi*; Hayashi, Nobuhiko; Urano, Hajime; Nakata, Motoki; Miyato, Naoaki; Takenaga, Hidenobu; Ide, Shunsuke; Kamada, Yutaka

Nuclear Fusion, 55(7), p.073014_1 - 073014_9, 2015/07

 Times Cited Count:13 Percentile:61.42(Physics, Fluids & Plasmas)

Conditions without the increases in the thermal and particle transport with ECH have been experimentally investigated in positive magnetic shear (PS), weak magnetic shear (WS) and reversed magnetic shear (RS) plasmas with internal transport barriers (ITBs) on JT-60U. The ion heat diffusivity around an internal transport barrier in the ion temperature ($$T_{rm i}$$-ITB) remains constant with ECH when a large negative toroidal rotation shear is formed before the ECH. The condition does not depend on the electron to ion temperature ratio ($$T_{rm e}$$/$$T_{rm i}$$) and ECH power. The electron heat diffusivity around a $$T_{rm e}$$-ITB stays constant with ECH when the magnetic shear is negative around the Te-ITB region. Effective particle transport remains constant or reduces during ECH under the condition of negative magnetic shear.

Journal Articles

Electronic structure of BaFeO$$_{3}$$ studied by X-ray spectroscopy

Mizumaki, Masaichiro*; Fujii, Hitoshi*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Uozumi, Takayuki*; Takano, Mikio*

Physica Status Solidi (C), 12(6), p.818 - 821, 2015/06

 Times Cited Count:8 Percentile:94.79

We investigated the electronic structure of BaFeO$$_{3}$$ by using HAXPES and XAS measurements and first principle studies. The experimental and theoretical results indicated that BaFeO$$_{3}$$ is a negative charge transfer compound. We concluded that the on-site Coulomb energy and the strong hybridization between Fe-3d and O-2p orbitals play a very important role of emergence of negative charge transfer. And we found the new structure in the Fe-2p XPS spectrum and concluded this structure is originated from non-local screening.

Journal Articles

Suppression of temperature hysteresis in negative thermal expansion compound BiNi$$_{1-x}$$Fe$$_{x}$$O$$_{3}$$ and zero-thermal expansion composite

Nabetani, Koichiro*; Muramatsu, Yuya*; Oka, Kengo*; Nakano, Kiho*; Hojo, Hajime*; Mizumaki, Masaichiro*; Agui, Akane; Higo, Yuji*; Hayashi, Naoaki*; Takano, Mikio*; et al.

Applied Physics Letters, 106(6), p.061912_1 - 061912_5, 2015/02

 Times Cited Count:48 Percentile:89.86(Physics, Applied)

Negative thermal expansion (NTE) of BiNi$$_{1_x}$$Fe$$_x$$O$$_3$$ is investigated by dilatometric curves, synchrotron X-ray diffraction, and X-ray absorption spectroscopy. All samples (x=0.05-0.15) shows large NTE with the coefficient of linear thermal expansion which induced by charge transfer between Bi$$^{5+}$$ and Ni$$^{2+}$$ in the controlled temperature range near room temperature. Compared with Bi$$_{1_x}$$Ln$$_x$$NiO$$_3$$ (Ln: rare-earth elements), the thermal hysteresis that causes a problem for practical application is suppressed because random distribution of Fe in the Ni site changes the first order transition to second order-like transition.

Journal Articles

Extension of kinetic-magnetohydrodynamic model to include toroidal rotation shear effect and its application to stability analysis of resistive wall modes

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go; Honda, Mitsuru; Hayashi, Nobuhiko; Ide, Shunsuke

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Extension of the kinetic-magnetohydrodynamic (MHD) model is presented to include toroidal rotation shear effect for the first time. The sheared rotation is introduced through generalization of the guiding center Lagrangian, yielding two additional terms in a quadratic form of mode-particle resonance. Additionally, another new term is introduced by using the equilibrium distribution function with rotation effect. These three terms are overlooked in conventional models. The new model is applied to stability analysis of resistive wall modes (RWMs) successfully. Numerical results show that the rotation shear reduces RWM growth rates further, which is consistent with experimental results.

Journal Articles

Magnetocaloric effect of field-induced ferromagnet BaFeO$$_{3}$$

Mizumaki, Masaichiro*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Takano, Mikio*

Journal of Applied Physics, 114(7), p.073901_1 - 073901_6, 2013/08

 Times Cited Count:19 Percentile:67.04(Physics, Applied)

We have investigated the magnetocaloric effect (MCE) of a perovskite oxide, BaFeO$$_{3}$$, that shows ferromagnetism by the aid of a small external field of about 0.3 T below the Curie temperature T$$_{C}$$ = 111 K. The magnetization is found to change almost reversibly in both field and temperature cycles. Hence, magnetic and thermal hysteretic losses are negligibly low during refrigeration, a property that is suitable for application. The reversible MCE is likely to arise from the absence of an orbital magnetic moment of Fe ions which are essentially in the Fe$$^{3+}$$L state (L: ligand hole). The magnetic entropy change and refrigerant capacity near the T$$_{C}$$ are about 5.8 J kg$$^{-1}$$ K$$^{-1}$$ and about 172 J kg$$^{-1}$$, respectively, both of which are comparable to those of ferromagnetic perovskite manganites. As BaFeO$$_{3}$$ contains no rare metals and is stable against corrosion, the material can be regarded as a candidate refrigerant material.

Journal Articles

Topotactic synthesis and crystal structure of a highly fluorinated Ruddlesden-Popper-type iron oxide, Sr$$_{3}$$Fe$$_{2}$$O$$_{5+x}$$F$$_{2-x}$$ (x $${approx}$$ 0.44)

Tsujimoto, Yoshihiro*; Yamaura, Kazunari*; Hayashi, Naoaki*; Kodama, Katsuaki; Igawa, Naoki; Matsushita, Yoshitaka*; Katsuya, Yoshio*; Shirako, Yuichi*; Akaogi, Masaki*; Muromachi, Eiji*

Chemistry of Materials, 23(16), p.3652 - 3658, 2011/08

 Times Cited Count:20 Percentile:57.31(Chemistry, Physical)

Topotactic reaction of the Ruddlesden-Popper phase Sr$$_{3}$$Fe$$_{2}$$O$$_{7-delta}$$ ($$delta$$ $${approx}$$ 0.18) with polytetrafluoroethylene yields a highly fluorinated phase Sr$$_{3}$$Fe$$_{2}$$O$$_{5+x}$$F$$_{2-x}$$ (x $${approx}$$ 0.44), compared with Sr$$_{3}$$Fe$$_{2}$$O$$_{6}$$F$$_{0.87}$$ prepared by the reaction of Sr$$_{3}$$Fe$$_{2}$$O$$_{6}$$ and F$$_{2}$$ gas. Structure analyses based on powder neutron diffraction, synchrotron powder diffraction, and $$^{57}$$Fe M$"o$ssbauer spectroscopy measurements demonstrate that the new oxyfluoride perovskite has no anion deficiencies and adopts the tetragonal structure (space group ${it I}$4/${it mmm}$) with lattice constants ${it a}$ = 3.87264(6) ${AA}$ and ${it c}$ = 21.3465(6) ${AA}$ at room temperature. The fluoride ions preferentially occupy the terminal apical anion sites with oxide ions in a disordered manner, which results in square pyramidal coordination around iron.

Journal Articles

Development of advanced tritium breeders and neutron multipliers for DEMO solid breeder blankets

Tsuchiya, Kunihiko; Hoshino, Tsuyoshi; Kawamura, Hiroshi; Mishima, Yoshinao*; Yoshida, Naoaki*; Terai, Takayuki*; Tanaka, Satoru*; Munakata, Kenzo*; Kato, Shigeru*; Uchida, Munenori*; et al.

Nuclear Fusion, 47(9), p.1300 - 1306, 2007/09

 Times Cited Count:18 Percentile:57.13(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Development of advanced tritium breeders and neutron multipliers for DEMO solid breeder blankets

Tsuchiya, Kunihiko; Hoshino, Tsuyoshi; Kawamura, Hiroshi; Mishima, Yoshinao*; Yoshida, Naoaki*; Terai, Takayuki*; Tanaka, Satoru*; Munakata, Kenzo*; Kato, Shigeru*; Uchida, Munenori*; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

no abstracts in English

Journal Articles

Overview of national centralized tokamak program; Mission, design and strategy to contribute ITER and DEMO

Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.

Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12

To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.

Journal Articles

Overview of the national centralized tokamak programme

Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.

Nuclear Fusion, 46(3), p.S29 - S38, 2006/03

 Times Cited Count:13 Percentile:44.28(Physics, Fluids & Plasmas)

The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.

Journal Articles

Engineering design and control scenario for steady-state high-beta operation in national centralized tokamak

Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.

Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02

 Times Cited Count:1 Percentile:10.64(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Design study of national centralized tokamak facility for the demonstration of steady state high-$$beta$$ plasma operation

Tamai, Hiroshi; Akiba, Masato; Azechi, Hiroshi*; Fujita, Takaaki; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; Hosogane, Nobuyuki; Ichimura, Makoto*; et al.

Nuclear Fusion, 45(12), p.1676 - 1683, 2005/12

 Times Cited Count:15 Percentile:48.09(Physics, Fluids & Plasmas)

Design studies are shown on the National Centralized Tokamak facility. The machine design is carried out to investigate the capability for the flexibility in aspect ratio and shape controllability for the demonstration of the high-beta steady state operation with nation-wide collaboration, in parallel with ITER towards DEMO. Two designs are proposed and assessed with respect to the physics requirements such as confinement, stability, current drive, divertor, and energetic particle confinement. The operation range in the aspect ratio and the plasma shape is widely enhanced in consistent with the sufficient divertor pumping. Evaluations of the plasma performance towards the determination of machine design are presented.

Journal Articles

Charge-ordered state in single-crystalline CaFeO$$_{3}$$ thin film studied by X-ray anomalous diffraction

Akao, Tadahiro*; Azuma, Yusuke; Usuda, Manabu; Nishihata, Yasuo; Mizuki, Junichiro; Hamada, Noriaki*; Hayashi, Naoaki*; Terashima, Takahito*; Takano, Mikio*

Physical Review Letters, 91(15), p.156405_1 - 156405_4, 2003/10

 Times Cited Count:31 Percentile:79.13(Physics, Multidisciplinary)

X-ray anomalous diffraction, together with a band structure calculation, was employed to obtain a quantitative comprehension of the charge-ordering state in a single-crystalline CaFeO$$_{3}$$ thin film. The experimental results show a characteristic energy dispersion of the near inhibited reflection at 150, implying Fe atoms split into two distinct states. The energy dispersion is in good agreement with the calculated spectrum based on LDA+U scheme. The calculation reveals an electronic configuration of the Fe 3d orbital follows a localization in the oxygen orbital surrounds one of the distinct Fe atoms.

Oral presentation

Topotactic synthesis and crystal structure of a fluorinated layered iron oxyfluoride

Tsujimoto, Yoshihiro*; Yamaura, Kazunari*; Matsushita, Yoshitaka*; Muromachi, Eiji*; Hayashi, Naoaki*; Kodama, Katsuaki; Igawa, Naoki; Shirako, Yuichi*; Akaogi, Masaki*

no journal, , 

Topotactic reaction of the n = 2 Ruddlesden-Popper phase Sr$$_{3}$$Fe$$_{2}$$O$$_{7-delta}$$ with the Teflon polymer yields a highly fluorinated phase Sr$$_{3}$$Fe$$_{2}$$O$$_{5+x}$$O$$_{2-x}$$ (x $$sim$$ 0.44). The crystal/magnetic structures and anion composition are determined by a combination of neutron diffraction and $$^{57}$$Fe M$"o$ssbauer spectroscopy experiments. Fluoride anions selectively occupy the terminal apical anion sites, leading to the square pyramidal coordination around the Fe metal center. The oxyfluoride material adopts a simple antiferromagnetic ordered structure with k = (1/2 1/2 0) below 390 K.

Oral presentation

Magnetocaloric effect and electronic structure of ferromagnetic perovskite BaFeO$$_{3}$$

Mizumaki, Masaichiro*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Takeuchi, Yayoi*; Takano, Mikio*

no journal, , 

BaFeO$$_{3}$$ is known to contain the rare valence state of iron, 4+. Although this system has been reported to be an antiferromagnet prepared in the conventional high pressure and high temperature method, the samples synthesized under low temperature oxidization was found to be ferromagnetic. BaFeO$$_{3}$$ shows a Curie temperature of 100 K; however, more details of magnetic properties have not been reported. In this study we report the magnetocaloric effect and the electronic structure of BaFeO$$_{3}$$.

Oral presentation

Magnetism and local structures of new ferromagnet BaFeO$$_{3}$$ and related materials

Yoshii, Kenji; Hayashi, Naoaki*; Matsumura, Daiju; Kusano, Shogo*; Mizumaki, Masaichiro*; Mizuki, Junichiro*; Takano, Mikio*

no journal, , 

We have investigated the magnetocaloric effect of BaFeO$$_{3}$$ and related materials. The substitutions at Ba and Fe sites was found to lead to a suppression of ground-state antiferromagnetic ordering. Hence, hysteretic losses are suppressed by the substitution, a property which is favorable to practical application. From EXAFS measurements using synchrotron radiation, BaFeO$$_{3}$$ involves a local structural distortion around Fe, whereas such behavior is suppressed by the substitutions. This may be related to the suppression of antiferromagnetic state, whose details will be presented at the conference.

Oral presentation

Magnetocaloric effect of field-induced ferromagnet BaFeO$$_{3}$$ and Fe-site-substituted materials

Yoshii, Kenji; Hayashi, Naoaki*; Mizumaki, Masaichiro*; Matsumura, Daiju; Takano, Mikio*

no journal, , 

We give an invited talk on the magnetocaloric effect (MCE) of new ferromagnetic oxide BaFeO$$_{3}$$. This oxide has a cubic structure and shows the Curie temperature of 110 K due to the ordering of Fe$$^{4+}$$ spins. The MCE measurements showed the large change of magnetic entropy of 5.8Jkg$$^{-1}$$K$$^{-1}$$ at around the Curie temperature. This is the largest value among the materials without rare earth elements. No thermal and field hysteresis was found, a property which is suitable for application, owing to small energy losses. This is attributed to the actual state of Fe ion of Fe$$^{3+}$$, having no orbital magnetic moment. We will briefly discuss the properties of Fe-site-substituted materials.

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