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Journal Articles

Giant multiple caloric effects in charge transition ferrimagnet

Kosugi, Yoshihisa*; Goto, Matato*; Tan, Z.*; Kan, Daisuke*; Isobe, Masahiko*; Yoshii, Kenji; Mizumaki, Masaichiro*; Fujita, Asaya*; Takagi, Hidenori*; Shimakawa, Yuichi*

Scientific Reports (Internet), 11(1), p.12682_1 - 12682_8, 2021/06

 Times Cited Count:1 Percentile:39.19(Multidisciplinary Sciences)

Caloric effects of solids provide more efficient and environment-friendly innovative refrigeration systems compared to the widely-used conventional vapor compressive cooling systems. Exploring novel caloric materials is challenging but critically important in developing future technologies. Here we discovered that the quadruple perovskite structure ferrimagnet BiCu$$_{3}$$Cr$$_{4}$$O$$_{12}$$ shows a large multicaloric effect at the first-order charge transition occurred around 190 K. Large latent heat and the corresponding isothermal entropy changes 28.2 J K$$^{-1}$$ kg$$^{-1}$$ can be fully utilized by applying both magnetic fields (magnetocaloric effect) and pressure (barocaloric effect). Adiabatic temperature changes reach 3.9 K for the 50 kOe magnetic field and 4.8 K for the 4.9 kbar pressure, and thus highly efficient thermal controls are achieved by multiple ways.

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

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:65.31(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

Pressure effect on intersite charge transfer in A-site-ordered double-perovskite-structure oxide

Long, Y.-W.*; Kawakami, Takateru*; Chen, W.-T.*; Saito, Takashi*; Watanuki, Tetsu; Nakakura, Yuta*; Liu, Q.-Q.*; Jin, C.-Q.*; Shimakawa, Yuichi*

Chemistry of Materials, 24(11), p.2235 - 2239, 2012/06

 Times Cited Count:32 Percentile:70.79(Chemistry, Physical)

An A-site ordered perovskite-structure oxide, LaCu$$_{3}$$Fe$$_{4}$$O$$_{12}$$, shows unusual intermetallic charge transfer between the A-site Cu and the B-site Fe ions. Like temperature, pressure also induces the intermetallic charge transfer at room temperature and the compound changes from low-pressure LaCu$$^{3+}$$$$_{3}$$Fe$$^{3+}$$$$_{4}$$O$$_{12}$$ to high-pressure LaCu$$^{2+}$$$$_{3}$$Fe$$^{3.75+}$$$$_{4}$$O$$_{12}$$ accompanying with significant volume collapse and as well as unusual softening in bulk modulus. In addition, the material was changed from an antiferromagnetic insulator to a paramagnetic metal transition. Either by physical or chemical (cation substitution) pressure, the charge-transfer transition temperature decreases, and the lower volume phase stabilizes Cu$$^{2+}$$ and Fe$$^{3.75+}$$ at the A and B sites, respectively.

Journal Articles

Colossal negative thermal expansion in BiNiO$$_{3}$$ induced by intermetallic charge transfer

Azuma, Masaki*; Chen, W.*; Seki, Hayato*; Czapski, M.*; Olga, S.*; Oka, Kengo*; Mizumaki, Masaichiro*; Watanuki, Tetsu; Ishimatsu, Naoki*; Kawamura, Naomi*; et al.

Nature Communications (Internet), 2, p.347_1 - 347_5, 2011/06

 Times Cited Count:307 Percentile:98.98(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

Antiferromagnetic interaction between A'-site Mn spins in A-site-ordered perovskite YMn$$_3$$Al$$_4$$O$$_{12}$$

Toyama, Takenori*; Saito, Takashi*; Mizumaki, Masaichiro*; Agui, Akane; Shimakawa, Yuichi*

Inorganic Chemistry, 49(5), p.2492 - 2495, 2010/01

 Times Cited Count:23 Percentile:70.58(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Various valence states of square-coordinated Mn in A-site-ordered perovskites

Long, Y.*; Saito, Takashi*; Mizumaki, Masaichiro*; Agui, Akane; Shimakawa, Yuichi*

Journal of the American Chemical Society, 131(44), p.16244 - 16247, 2009/10

 Times Cited Count:52 Percentile:77.94(Chemistry, Multidisciplinary)

A-site-ordered perovskites LaMn$$_{3}$$Cr$$_{4}$$O$$_{12}$$ and LaMn$$_{3}$$Ti$$_{4}$$O$$_{12}$$ were synthesized under high-pressure and high-temperature conditions. The charge formula of LaMn$$_{3}$$Cr$$_{4}$$O$$_{12}$$ was found to be LaMn$$_{3}$$Cr$$_{4}$$O$$_{12}$$ with Mn$$^{3+}$$ at the square-coordinated A site. The valence of the A-site Mn ions in LaMnTi$$_{4}$$O$$_{12}$$ appeared to be less than +2, and the charge combination in this compound seemed to be LaMnTi$$_{4}$$O$$_{12}$$. Although the square-coordinated A site in A-site-ordered perovskites has been widely known to be occupied by Jahn-Teller active Mn$$^{3+}$$, the present results show that the valence of Mn at the A site can vary from +3 to possible +1.67.

Journal Articles

Synthesis, crystal structure, and magnetic properties of Bi$$_3$$Mn$$_4$$O$$_{12}$$(NO$$_3$$) oxynitrate comprising $$S$$=3/2 honeycomb lattice

Smirnova, O.*; Azuma, Masaki*; Kumada, Nobuhiro*; Kusano, Yoshihiro*; Matsuda, Masaaki; Shimakawa, Yuichi*; Takei, Takahiro*; Yonesaki, Yoshinori*; Kinomura, Nobukazu*

Journal of the American Chemical Society, 131(23), p.8313 - 8317, 2009/05

 Times Cited Count:114 Percentile:91.45(Chemistry, Multidisciplinary)

Neutron diffraction and FT-IR analysis revealed that the novel oxynitrate Bi$$_3$$Mn$$_4$$O$$_{12}$$ (NO$$_3$$) prepared by hydrothermal synthesis is of a new structural type including flat NO$$_3$$ layers alternating with blocks of two PbSb$$_2$$O$$_6$$-like layers. Mn$$^{4+}$$ ($$S$$=3/2) forms a regular honeycomb lattice, and magnetic susceptibility data indicated two-dimensional magnetism. Despite its Weiss constant of $$-$$257K, no long-range ordering was observed down to 0.4K because of the magnetic frustration due to the competition between the nearest and the next-nearest antiferromagnetic interactions.

Journal Articles

Assessment of calculation model for annular core on the HTTR

Nojiri, Naoki; Handa, Yuichi*; Shimakawa, Satoshi; Goto, Minoru; Kaneko, Yoshihiko*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 5(3), p.241 - 250, 2006/09

It was shown from the annular core experiment of the HTTR that the discrepancy of excess reactivity between experiment and analysis reached about 3 % Dk/k at maximum. Sensitivity analysis for the annular core of the HTTR was performed to improve the discrepancy. The SRAC code system was used for the core analysis. As the results of the analysis, it was found clearly that the multiplication factor of the annular core is affected by (1) mesh interval in the core diffusion calculation, (2) mesh structure of graphite region in fuel lattice cell and (3) the Benoist's anisotropic diffusion coefficients. The significantly large discrepancy previously reported was reduced down to about 1 % Dk/k by the revised annular core model.

Journal Articles

Neutron powder diffraction study on the crystal and magnetic structures of BiCoO$$_3$$

Belik, A. A.*; Iikubo, Satoshi; Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Niitaka, Seiji*; Azuma, Masaki*; Shimakawa, Yuichi*; Takano, Mikio*; Izumi, Fujio*; et al.

Chemistry of Materials, 18(3), p.798 - 803, 2006/02

 Times Cited Count:254 Percentile:98.59(Chemistry, Physical)

The crystal and magnetic structures of polycrystalline BiCoO$$_3$$ have been determined by the Rietveldmethod from neutron diffraction data measured at temperatures from 5 to 520 K. BiCoO$$_3$$ (space groupP4mm; Z=1; a=3.72937(7) ${AA}$ and c=4.72382(15) ${AA}$ at room temperature; tetragonality c/a=1.267) is isotypic with BaTiO$$_3$$ and PbTiO$$_3$$ in the whole temperature range. BiCoO$$_3$$ is an insulator with a Neeltemperature of 470 K. A possible model for antiferromagnetic order is proposed with a propagationvector of k=(1/2, 1/2, 0). In this model, magnetic moments of Co$$^{3+}$$ ions are parallel to the c directionand align antiferromagnetically in the ab plane. The antiferromagnetic ab layers stack ferromagneticallyalong the c axis, forming a C-type antiferromagnetic structure. Refined magnetic moments at 5 and 300K are 3.24(2)$$mu$$$$_B$$ and 2.93(2)$$mu$$$$_B$$, respectively. The structure refinements revealed no deviation fromstoichiometry in BiCoO$$_3$$. BiCoO$$_3$$ decomposed in air above 720 K to give Co$$_3$$O$$_4$$ and sillenite-like Bi$$_{25}$$CoO$$_{39}$$.

Oral presentation

Direct observation of the Ni-3d electronic states change in PrNiO$$_{3}$$

Mizumaki, Masaichiro*; Agui, Akane; Saito, Takashi*; Azuma, Masaki*; Shimakawa, Yuichi*; Takano, Mikio*; Uozumi, Takayuki*

no journal, , 

no abstracts in English

Oral presentation

The Electronic property of A-site perovscaite LaMn$$_{3}$$B$$_{4}$$O$$_{12}$$ (B=Ti,V,Cr)

Saito, Takashi*; Lon, Y.*; Mizumaki, Masaichiro*; Agui, Akane; Shimakawa, Yuichi*

no journal, , 

no abstracts in English

Oral presentation

Soft X-ray emission spectroscopy of SrFeO$$_{2}$$

Mizumaki, Masaichiro*; Agui, Akane; Uozumi, Takayuki*; Inoue, Akira*; Kawai, Masanori*; Ichikawa, Noriya*; Shimakawa, Yuichi*

no journal, , 

no abstracts in English

Oral presentation

Observation of the electronic excitation structure for SrFeO$$_{2}$$ by using a soft X-ray emission spectroscopy

Mizumaki, Masaichiro*; Agui, Akane; Uozumi, Takayuki*; Ichikawa, Noriya*; Shimakawa, Yuichi*

no journal, , 

no abstracts in English

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$$_{3}$$.

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