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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

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

Intermetallic charge transfer in MTiO$$_{3}$$ (M = Mn, Fe, Co, and Ni) by Ti2p edge resonant inelastic X-ray scattering

Agui, Akane; Mizumaki, Masaichiro*; Uozumi, Takayuki*

Journal of Electron Spectroscopy and Related Phenomena, 205, p.106 - 110, 2015/11

 Times Cited Count:5 Percentile:37.34(Spectroscopy)

In this study, we have measured the Ti 2p edge resonant inelastic X-ray scattering spectra of MTiO3 (M= Mn, Fe, Co, and Ni) in order to investigate the intermetallic M 3d-Ti 3d charge transfer. We found the peak around -4.5 eV in the energy loss scale for all MTiO$$_{3}$$ and additionally found that only FeTiO$$_{3}$$ has a peak at at -2.5 eV. Those peaks are attributed to the M 3d-Ti 3d charge transfer.

Journal Articles

X-ray absorption spectroscopy in the heavy Fermion compound $$alpha$$-YbAlB$$_4$$ at high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of the Physical Society of Japan, 84(11), p.114715_1 - 114715_4, 2015/11

 Times Cited Count:2 Percentile:24.12(Physics, Multidisciplinary)

Journal Articles

Melting of Pb charge glass and simultaneous Pb-Cr charge transfer in PbCrO$$_{3}$$ as the origin of volume collapse

Yu, R.*; Hojo, Hajime*; Watanuki, Tetsu; Mizumaki, Masaichiro*; Mizokawa, Takashi*; Oka, Kengo*; Kim, H.*; Machida, Akihiko; Sakaki, Koji*; Nakamura, Yumiko*; et al.

Journal of the American Chemical Society, 137(39), p.12719 - 12728, 2015/10

 Times Cited Count:23 Percentile:65.97(Chemistry, Multidisciplinary)

no abstracts in English

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

Thermal expansion of a Au-Al-Yb intermediate valence quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Ishimasa, Tsutomu*; Machida, Akihiko; Yamamoto, Shin*; Tanaka, Yukinori*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Watanabe, Shinji*

Solid State Communications, 211, p.19 - 22, 2015/06

 Times Cited Count:5 Percentile:28.49(Physics, Condensed Matter)

The thermal expansion of a Au-Al-Yb intermediate-valence quasicrystal has been studied by X-ray diffraction measurements. We have found anomalous thermal expansion behavior, namely zero thermal expansion below 50 K. By comparison with an isostructural Au-Al-Tm quasicrystal, the contribution of the Yb valence variation was extracted, and it was shown that its negative thermal expansion component due to the valence shift toward the divalent state by cooling compensated for the positive thermal expansion of the original lattice.

Journal Articles

Synchrotron X-ray spectroscopy study on the valence state and magnetization in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$) at low temperatures and high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of Physics; Conference Series, 592(1), p.012020_1 - 012020_6, 2015/03

 Times Cited Count:1 Percentile:46.84

Valence fluctuation phenomena in rare-earth intermetallic compounds have attracted attention because the quantum criticality of the valence transition has been proposed theoretically. Recently, it was found that $$beta$$-YbAlB$$_4$$ shows quantum criticality without tuning and has a strong mixed-valence state. In this study, we measured the magnetization curve and X-ray magnetoabsorption in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$), which is a locally isostructural polymorph of $$beta$$-YbAlB$$_4$$. The magnetization and X-ray experiments were performed in fields up to 55 and 40 T, respectively. A small increase in the Yb valence was observed at fields where the magnetization curve exhibited a change in slope.

Journal Articles

X-ray absorption spectroscopy and novel electronic properties in heavy fermion compounds YbT$$_{2}$$Zn$$_{20}$$ (T: Rh and Ir)

Honda, Fuminori*; Hirose, Yusuke*; Miyake, Atsushi*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Tsutsui, Satoshi*; Watanuki, Tetsu; Watanabe, Shinji*; Takeuchi, Tetsuya*; Settai, Rikio*; et al.

Journal of Physics; Conference Series, 592(1), p.012021_1 - 012021_5, 2015/03

 Times Cited Count:2 Percentile:65.76

no abstracts in English

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

Structure refinement for the $$alpha$$-$$varepsilon$$ transition of iron by using EXAFS

Ishimatsu, Naoki*; Sata,Yusuke*; Maruyama, Hiroshi*; Watanuki, Tetsu; Kawamura, Naomi*; Mizumaki, Masaichiro*; Irifune, Tetsuo*; Sumiya, Hitoshi*

Hoshako, 28(1), p.3 - 11, 2015/01

no abstracts in English

Journal Articles

Temperature and polarization dependence of Fe L$$_{3}$$-edge X-ray absorption spectra of LuFe$$_{2}$$O$$_{4}$$

Agui, Akane; Mizumaki, Masaichiro*; Kuroda, Tomoko*; Kawai, Masahiro*; Nagata, Tomoko*; Ikeda, Naoshi*; Uozumi, Takayuki*

Journal of Electron Spectroscopy and Related Phenomena, 197, p.13 - 16, 2014/12

 Times Cited Count:4 Percentile:29.63(Spectroscopy)

In this paper, we report on the study of the temperature dependence of Fe L$$_{3}$$-edge X-ray absorption spectra (XAS) of LuFe$$_{2}$$O$$_{4}$$. In the charge ordered state the valence of Fe is in Fe$$^{2+}$$ and Fe$$^{3+}$$. And the Fe L$$_{3}$$-edge XAS spectra have double peak structure which is attributed the Fe$$^{2+}$$ and Fe$$^{3+}$$ state. In high temperature, the double peak structure becomes indistinct because the thermal excited state overlaps while the Fe valence keeping the integer number.

Journal Articles

Temperature and magnetic field dependent Yb valence in YbRh$$_2$$Si$$_2$$ observed by X-ray absorption spectroscopy

Nakai, Hirohito*; Ebihara, Takao*; Tsutsui, Satoshi*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Michimura, Shinji*; Inami, Toshiya; Nakamura, Toshiyuki*; Kondo, Akihiro*; Kindo, Koichi*; et al.

Journal of the Physical Society of Japan, 82(12), p.124712_1 - 124712_5, 2013/12

 Times Cited Count:7 Percentile:51.13(Physics, Multidisciplinary)

The temperature and magnetic field dependences of Yb valence were observed in the heavy fermion compoundYbRh$$_2$$Si$$_2$$ by X-ray absorption spectroscopy. The measurements revealed that the Yb valence decreases with decreasing temperature in the range from 200 to 2 K and increases with increasing magnetic field in the range from 0 to 33 T without showing an abrupt change in the Yb valence. The Yb valence is in the range from 2.92 to 2.96 depending on temperature and magnetic field. With respect to the valence being 2.92 at 0 T and 2.93 at 33 T in 2 K, YbRh$$_2$$Si$$_2$$ is a valence fluctuation compound and does not reach the integer trivalent state at high magnetic field. These results endorse the conventional knowledge that the valence of Yb is very close to the integer value of 3+, decreases with decreasing temperature, and becomes closer to 3+ with increasing magnetic field.

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

Synchrotron X-ray spectroscopy study on the valence state in $$alpha$$- and $$beta$$-TbAlB$$_4$$ at low temperature and high magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Kuga, Kentaro*; Nakatsuji, Satoru*; Michimura, Shinji*; Inami, Toshiya; Kawamura, Naomi*; Mizumaki, Masaichiro*

Journal of the Korean Physical Society, 62(12), p.1778 - 1781, 2013/06

 Times Cited Count:9 Percentile:57.28(Physics, Multidisciplinary)

The valence state of Yb ions in $$alpha$$- and $$beta$$-YbAlB$$_4$$ has been investigated by X-ray absorption and emission spectroscopy at temperatures from 2 to 280 K. It is found that the valence gradually increases with increasing temperature toward 3+ and that the characteristic temperature of the valence fluctuations is about 290 K. We also observe a small increase in the Yb valence ($$sim$$ 0.002) in $$beta$$-YbAlB$$_4$$ by a magnetic field of 32 T at 40 K.

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

 Times Cited Count:13 Percentile:97.61

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

Oxygen hole state in A-site ordered perovskite ACu$$_3$$Ru$$_4$$O$$_{12}$$ (A = Na, Ca, and La) probed by resonant X-ray emission spectroscopy

Mizumaki, Masaichiro*; Mizokawa, Takashi*; Agui, Akane; Tanaka, Sotaro*; Takatsu, Hiroshi*; Yonezawa, Shingo*; Maeno, Yoshiteru*

Journal of the Physical Society of Japan, 82(2), p.024709_1 - 024709_6, 2013/02

 Times Cited Count:7 Percentile:51.13(Physics, Multidisciplinary)

In this study, we report the O 1$$s$$ and Cu 2$$p$$ X-ray absorption spectroscopy (XAS) and resonant X-ray emission spectroscopy (RXES) study on the A-site ordered perovskite ACu$$_3$$Ru$$_4$$O$$_{12}$$ (A = Na, Ca, and La). Hartree-Fock calculation and cluster model calculation were carried out to analyze O 1$$s$$ and Cu 2$$p$$ XAS spectra. The O 1$$s$$ RXES spectra indicate that the number of O 2$$p$$ holes increases in going from La to Ca to Na. In addition, the Cu 2$$p$$ RXES spectra reveal that the charge-transfer energy decreases in going from La to Ca to Na.

Journal Articles

High-magnetic-field X-ray absorption and magnetic circular dichroism spectroscopy in the mixed-valent compound YbAgCu$$_4$$

Nakamura, Toshiyuki*; Matsuda, Yasuhiro*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(11), p.114702_1 - 114702_11, 2012/11

 Times Cited Count:11 Percentile:60.72(Physics, Multidisciplinary)

The X-ray absorption and magnetic circular dichroism (MCD) spectra at the Yb L$$_3$$ edge were measured in the mixed-valent heavy fermion compound YbAgCu$$_4$$ at high magnetic fields and low temperatures. The magnetic-field-temperature (H-T) phase boundary determined by the valence state is in very good agreement with that determined by the magnetization. It is clearly found that the metamagnetism of this compound is due to the field induced valence transition. A distinctive positive peak of the XMCD spectra appears in the vicinity of the white line of the absorption due to Yb$$^{3+}$$ state, while no feature is observed in the XMCD spectra corresponding to the Yb$$^{2+}$$ state. A small negative XMCD peak was observed at a lower energy and was attributed to the quadrupole trasition from theoretical calcuration, which explains its peculicar magnetic field dependence.

Journal Articles

Valence fluctuation in YbAgCu$$_4$$ at high Magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(1), p.015002_1 - 015002_2, 2012/01

 Times Cited Count:10 Percentile:58.4(Physics, Multidisciplinary)

The valence change of Yb ion in YbAgCu$$_4$$ was measured by means of X-ray absorption spectroscopy under high magnetic fields up to 35T. The valence state of Yb in YbAgCu$$_4$$ at 4.8K significantly increases at the metamagnetic transition. The saturation value of $$v$$ at 55T is evaluated as 2.97 using the relation $$Delta M/Delta v$$ at 35T. This value is in good agreement with $$v$$ for the related compound YbInCu$$_4$$ at high temperatures and the Yb valence in the localized high-field phase. We conclude that the metamagnetic transition in YbAgCu$$_4$$ arises from the valence transition, as theoretically predicted.

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