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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:0 Percentile:0(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

Analysis of glass behavior of Lu$$_{2}$$Fe$$_{3}$$O$$_{7}$$ with distributed equivalent circuit model

Fukada, Yukimasa*; Fukuyama, Ryota*; Fujiwara, Kosuke*; Yoshii, Kenji; Shigematsu, Kei*; Azuma, Masaki*; Ikeda, Naoshi*

Journal of the Physical Society of Japan, 90(2), p.024710_1 - 024710_6, 2021/02

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

We report an analysis of the dielectric glasslike state of the spin- and charge-ordered system Lu$$_{2}$$Fe$$_{3}$$O$$_{7}$$, which has structural and physical properties analogous to those of the electronic ferroelectrics ${it R}$Fe$$_{2}$$O$$_{4}$$ (${it R}$: rare earth). Aging and memory effects of resistivity were found in the electric impedance response. We performed a numerical analysis with equivalent electric circuits that have a logarithmic Gaussian distribution of resistance and capacitance. The distribution parameters well explained the glassy nature of the electric and dielectric properties between 100 and 200 K and the distribution variations of charge- and magnetic-ordered domains underlying the glass nature.

Journal Articles

Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions

Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Ieda, Junichi; Saito, Eiji

Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08

 Times Cited Count:0 Percentile:0(Physics, Applied)

Journal Articles

Hard X-ray photoelectron spectroscopy study of Pt/Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$

Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Kawasaki, Ikuto; Okane, Tetsuo; Yamagami, Hiroshi; Yaita, Tsuyoshi; Harii, Kazuya; Ieda, Junichi; Okayasu, Satoru; et al.

JPS Conference Proceedings (Internet), 30, p.011192_1 - 011192_6, 2020/03

High energy X-ray photoelectron spectroscopy (HAXPES) measurements were carried out for the Spin Seebeck system Pt/Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$(YIG). This system was found to show anomalous Hall effect, possible due to the formation of intermetallic compounds between Fe$$^{3+}$$ and Pt. To reveal this possibility, we have measured the Fe 1s photoelectron peaks by using HAXPES. It was found that the Fe ions consist of Fe$$^{3+}$$ in YIG and metallic Fe. The formation of the metallic state is consistent with the proposed origin of the anomalous Hall effect. Other spectra such as Pt 4f will be presented at the conference.

Journal Articles

Weak-coupling mean-field theory of magnetic properties of NiGa$$_{2}$$S$$_{4}$$

Nomura, Takuji*; Yamamoto, Yuji*; Yoshii, Kenji

Journal of the Physical Society of Japan, 89(2), p.024704_1 - 024704_10, 2020/02

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

We report a mean-field theoretical study of a triangular magnet NiGa$$_{2}$$S$$_{4}$$. Using the localized Wannier functions obtained from a band calculation, the most stable magnetic state was found to be spiral with the incommensurate structure, consistent with the result from neutron diffraction. The Ni-site Coulomb interaction was not strong (U about 2 eV). The spin value at the Ni site was also not so large about 1.1 mb. These results mean that the hybridization between Ni and S may play an important role. The dynamical spin correlation function was found to in accord with the results from neutron scattering.

Journal Articles

X-ray absorption spectroscopy and magnetocaloric study of Pr$$_{1-x}$$Sr$$_{x}$$CoO$$_{3}$$ (0$$leq x leq$$0.5)

Matsumura, Daiju; Tsuji, Takuya; Yoshii, Kenji

Materials Chemistry and Physics, 238, p.121885_1 - 121885_5, 2019/12

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

We have conducted X-ray absorption spectroscopy study for perovskite cobaltite Pr$$_{1-x}$$Sr$$_{x}$$CoO$$_{3}$$ (0$$leq x leq$$0.5) to understand Sr doping effect and magnetocaloric measurement for Pr$$_{0.5}$$Sr$$_{0.5}$$CoO$$_{3}$$ to reveal the origin of magnetic anomaly at around 110 K. The extended X-ray absorption fine structure (EXAFS) measurements at the Co ${it K}$-edge suggest that the average valence value of Co ions increases, the interatomic distance of Co-O bonding decreases, and the local distortion of CoO$$_{6}$$ octahedron increases as Sr is doped in PrCoO$$_{3}$$. The interatomic distance of Co-O bonding shrinks more greatly for the larger doping region. No temperature dependent electronic and structural changes were observed from Co ${it K}$-edge X-ray absorption spectra in the whole thermal range studied (17-300 K). The magnetocaloric effect of Pr$$_{0.5}$$Sr$$_{0.5}$$CoO$$_{3}$$ indicates the change of magnetic structure at 110 K.

Journal Articles

Dielectric and magnetocaloric study of TmCrO$$_{3}$$

Yoshii, Kenji; Ikeda, Naoshi*

Journal of Alloys and Compounds, 804, p.364 - 369, 2019/10

 Times Cited Count:6 Percentile:60.45(Chemistry, Physical)

Dielectric and magnetocaloric measurements are carried out for the chromite TmCrO$$_{3}$$. This oxide was reported to be multiferroic below the N$'e$el temperature ($$T_{rm N}$$) of 125 K, likely due to a structural transformation. The dielectric response shows large dielectric constants below 300 K. However, from the analyses of loss tangent, AC conductivity and dielectric modulus, this behavior is rooted in hopping of charge carriers rather than electric dipoles, as proposed for some other chromites. No dielectric anomaly is found at $$T_{rm N}$$. The magnetocaloric effect shows that the magnetic transitions at $$T_{rm N}$$ as well as the spin reorientation temperature are of a second order. This result strongly suggests the absence of magnetostructural transition at $$T_{rm N}$$ in accord with no observation of ferroelectric transition at this temperature.

Journal Articles

Spin rotation, glassy state, and magnetization switching in ${it R}$CrO$$_{3}$$ (${it R}$=La$$_{1-x}$$Pr$$_{x}$$, Gd, and Tm); Reinvestigation of magnetization reversal

Yoshii, Kenji

Journal of Applied Physics, 126(12), p.123904_1 - 123904_8, 2019/09

 Times Cited Count:5 Percentile:51.19(Physics, Applied)

We have reinvestigated the magnetization reversal in perovskites La$$_{1-x}$$Pr$$_{x}$$CrO$$_{3}$$, GdCrO$$_{3}$$, and TmCrO$$_{3}$$ and show that spin rotation or reorientation plays a key role in this property. The magnetization measurements on all systems show the appearance and disappearance of the reversal are commonly depend on a strength of a Zeeman energy at the rare earth site in analogy with spin rotation in GdCrO$$_{3}$$ and TmCrO$$_{3}$$, denoted at the spin reorientation. Magnetic susceptibility measurements point to either superparamagnetic or single-molecule-magnet-like glassy behavior in all three systems, which is likely linked to a rotation of the R$$^{3+}$$-Cr$$^{3+}$$ coupling, as seen from magnetocalorimetry ($$R$$ = La$$_{1-x}$$Pr$$_{x}$$, Gd, and Tm). We also present a characteristic magnetization switching by rotating the R$$^{3+}$$ moments with the aid of large Zeeman energies.

Journal Articles

Electrical and crystallographic study of an electrothermodynamic cycle for a waste heat recovery

Kim, J.*; Yamanaka, Satoru*; Nakajima, Akira*; Kato, Takanori*; Kim, Y.*; Fukuda, Tatsuo; Yoshii, Kenji; Nishihata, Yasuo; Baba, Masaaki*; Takeda, Masatoshi*; et al.

Advanced Sustainable Systems (Internet), 2(11), p.1800067_1 - 1800067_8, 2018/11

 Times Cited Count:1 Percentile:11.84(Green & Sustainable Science & Technology)

Journal Articles

Pyroelectric power generation with ferroelectrics (1-x)PMN-xPT

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

 Times Cited Count:6 Percentile:41.1(Materials Science, Multidisciplinary)

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

Relationship between the material properties and pyroelectric-generating performance of PZTs

Yamanaka, Satoru*; Kim, J.*; Nakajima, Akira*; Kato, Takanori*; Kim, Y.*; Fukuda, Tatsuo; Yoshii, Kenji; Nishihata, Yasuo; Baba, Masaaki*; Yamada, Noboru*; et al.

Advanced Sustainable Systems (Internet), 1(3-4), p.1600020_1 - 1600020_6, 2017/04

no abstracts in English

Journal Articles

Absence of a polar phase in perovskite chromite $$R$$CrO$$_{3}$$ ($$R$$=La and Pr)

Yoshii, Kenji; Ikeda, Naoshi*; Shimojo, Yutaka; Ishii, Yoshinobu*

Materials Chemistry and Physics, 190, p.96 - 101, 2017/04

 Times Cited Count:12 Percentile:54.62(Materials Science, Multidisciplinary)

Magnetic and dielectric properties have been studied for LaCrO$$_{3}$$, PrCrO$$_{3}$$, and their solid solution La$$_{0.5}$$Pr$$_{0.5}$$CrO$$_{3}$$, belonging to a family of ferroelectricorthochromite series $${it R}$$CrO$$_{3}$$ ($${it R}$$: rare earths). The magnetic measurements confirm that the material shows canted antiferromagnetic ordering at 240-288 K. Neutron diffraction patterns could be fitted with the centrosymmetric $${it Pnma}$$, which is different from the non-centrosymmetric structure proposed for the ferroelectric phase of NdCrO$$_{3}$$. The large dielectric constants are likely due to the hopping of charge carriers as proposed previously for other chromites.

Journal Articles

Current status of research and development at Japan Atomic Energy Agency

Fujita, Yuji; Yoshii, Kenji

Denki Hyoron, 101(2), p.43 - 58, 2016/02

Japan Atomic Energy Agency (JAEA) is conducting many kinds of research activities, including fundamental and applied researches, and project studies to create novel technologies and industries. In particular, the activities are mainly focused on the R&D studies for recovery from the Fukushima Daiichi Nuclear NPS accident, safety researches, the development of fast reactor cycles, and high-level radioactive waste disposal. This article gives reviews on current status of the researches of JAEA in this fiscal year.

Journal Articles

Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates

Torigoe, Shuhei*; Ishimoto, Yutaro*; Aoishi, Yuhei*; Murakawa, Hiroshi*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo; Kodama, Katsuaki; Tomiyasu, Keisuke*; et al.

Physical Review B, 93(8), p.085109_1 - 085109_5, 2016/02

 Times Cited Count:4 Percentile:26.78(Materials Science, Multidisciplinary)

Journal Articles

Novel electrothermodynamic power generation

Kim, Y.*; Kim, J.*; Yamanaka, Satoru*; Nakajima, Akira*; Ogawa, Takashi*; Serizawa, Takeshi*; Tanaka, Hirohisa*; Baba, Masaaki*; Fukuda, Tatsuo; Yoshii, Kenji; et al.

Advanced Energy Materials, 5(13), p.1401942_1 - 1401942_6, 2015/07

 Times Cited Count:8 Percentile:41.84(Chemistry, Physical)

An innovative electro-thermodynamic cycle based on temporal temperature variations using pyroelectric effect has been presented. Practical energy is successfully generated in both $textit{in-situ}$ synchrotron X-ray diffraction measurements under controlled conditions and $textit{Operando}$ real engine dynamometer experiments. The main generating origin is revealed as a combination of a crystal structure change and dipole change phenomenon corresponds to the temperature variation. In particular, the electric field induced 180$$^circ$$ domain switching extremely improves generating power, and the true energy breakeven with temperature variation is firstly achieved.

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

 Times Cited Count:0 Percentile:0.04

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

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

Local structure around cesium in montmorillonite, vermiculite and zeolite under wet condition

Tsuji, Takuya; Matsumura, Daiju; Kobayashi, Toru; Suzuki, Shinichi; Yoshii, Kenji; Nishihata, Yasuo; Yaita, Tsuyoshi

Clay Science, 18(4), p.93 - 97, 2014/12

Journal Articles

Present status of J-PARC linac

Oguri, Hidetomo; Hasegawa, Kazuo; Ito, Takashi; Chishiro, Etsuji; Hirano, Koichiro; Morishita, Takatoshi; Shinozaki, Shinichi; Ao, Hiroyuki; Okoshi, Kiyonori; Kondo, Yasuhiro; et al.

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.389 - 393, 2014/10

no abstracts in English

246 (Records 1-20 displayed on this page)