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Journal Articles

Effects of diluents on the separation of minor actinides from lanthanides with tetradodecyl-1,10-phenanthroline-2,9-diamide from nitric acid medium

Tsutsui, Nao; Ban, Yasutoshi; Suzuki, Hideya*; Nakase, Masahiko*; Ito, Sayumi*; Inaba, Yusuke*; Matsumura, Tatsuro; Takeshita, Kenji*

Analytical Sciences, 36(2), p.241 - 246, 2020/02

 Times Cited Count:5 Percentile:41.67(Chemistry, Analytical)

To investigate the effective separation of actinides (Ans) from lanthanides (Lns), single-stage batch extraction experiments were performed with a novel extractant, tetradodecyl-1,10-phenanthroline-2,9-diamide (TDdPTDA) with various diluents such as 3-nitrobenzotrifluoride (F-3), nitrobenzene, and ${it n}$-dodecane for Am, Cm, and Lns. The extraction kinetics with TDdPTDA was rapid enough to perform the actual extraction flow sheet. The slopes of the distribution ratio versus TDdPTDA concentration and the distribution ratio versus nitric acid concentration were similar for F-3 and nitrobenzene systems but different from ${it n}$-dodecane system. These differences were attributed to the characteristics of the diluents. This study reveals high distribution ratios of Am (${it D}$ $$_{Am}$$) and Cm (${it D}$ $$_{Cm}$$) for TDdPTDA, with the high separation factors (${it SF}$s) of Am from Lns enough for their separation.

Journal Articles

Effect of $$B$$-site randomness on the antiferroelectric/relaxor nature of the ground state; Diffuse and inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$

Owada, Kenji*; Tsukada, Shinya*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro*; Owa, Hidehiro*; Yasuda, Naohiko*; Terauchi, Hikaru*

Physical Review B, 98(5), p.054106_1 - 054106_10, 2018/08

 Times Cited Count:2 Percentile:16.65(Materials Science, Multidisciplinary)

Journal Articles

Observation of momentum-dependent charge excitations in hole-doped cuprates using resonant inelastic X-ray scattering at the oxygen $$K$$ edge

Ishii, Kenji*; Toyama, Takami*; Asano, Shun*; Sato, Kentaro*; Fujita, Masaki*; Wakimoto, Shuichi; Tsutsui, Kenji*; Sota, Shigetoshi*; Miyawaki, Jun*; Niwa, Hideharu*; et al.

Physical Review B, 96(11), p.115148_1 - 115148_8, 2017/09

AA2017-0402.pdf:0.81MB

 Times Cited Count:20 Percentile:75.96(Materials Science, Multidisciplinary)

Journal Articles

Orbital-selective electronic excitations in iron arsenides revealed by simulated nonresonant inelastic X-ray scattering

Tsutsui, Kenji; Kaneshita, Eiji*; Toyama, Takami*

Physical Review B, 92(19), p.195103_1 - 195103_5, 2015/11

 Times Cited Count:2 Percentile:12.06(Materials Science, Multidisciplinary)

Nonresonant inelastic X-ray scattering (NIXS) is a possible tool to detect charge excitations in electron systems. In addition, multipole transitions at high-momentum-transfer region open a new possibility to determine orbital-selective electronic excitations in multi-orbital itinerant 3$$d$$ electron systems. As a theoretical example, we chose the antiferromagnetic state of iron arsenides and demonstrate that the orbital-selective excitations are detectable by choosing appropriate momentum transfer in NIXS. We propose that both NIXS and resonant inelastic X-ray scattering are complementary to each other for fully understanding the nature of orbital excitations in multi-orbital itinerant electron systems.

Journal Articles

Enhanced charge excitations in electron-doped cuprates by resonant inelastic X-ray scattering

Toyama, Takami*; Tsutsui, Kenji; Mori, Michiyasu; Sota, Shigetoshi*; Yunoki, Seiji*

Physical Review B, 92(1), p.014515_1 - 014515_8, 2015/07

 Times Cited Count:12 Percentile:54.76(Materials Science, Multidisciplinary)

Resonant inelastic X-ray scattering (RIXS) tuned for Cu $$L$$ edge is a possible tool to detect charge excitations in cuprate superconductors. We theoretically investigate the possibility for observing a collective charge excitation by the RIXS. The RIXS process via the intermediate state inevitably makes the spectral weight of charge excitation stronger in electron doping than in hole doping. Electron-hole asymmetry also appears in dynamical charge structure factor, showing a new enhanced small-momentum low-energy mode in electron doping. These facts indicate a possibility of detecting the new charge mode by RIXS in electron-doped systems.

Journal Articles

Theoretical study of electronic states and excitation spectra in Ni-substituted cuprates

Tsutsui, Kenji; Toyama, Takami*; Maekawa, Sadamichi

JPS Conference Proceedings (Internet), 3, p.017008_1 - 017008_6, 2014/06

Impurity substitution for copper in high-Tc cuprate superconductors has attracted much attention. For Ni substitution, it has been argued from several experiments that hole carriers are strongly localized at around Ni sites. We have demonstrated theoretically that a hole can be bound in the NiO$$_{4}$$ plaquette forming the Zhang-Rice doublet. In this study, we examine the interaction between the Zhang-Rice doublet and hole carriers. We carry out the numerically exact diagonalization on small clusters of the d-p model with a Ni impurity site and calculate the resonant inelastic X-ray scattering spectra for Ni K-edge.

Journal Articles

Optical conductivity of antiferromagnetic metallic chromium; Mean-field calculation for the multi-orbital Hubbard model

Sugimoto, Kodai*; Toyama, Takami*; Kaneshita, Eiji*; Tsutsui, Kenji

Journal of the Korean Physical Society, 63(3), p.632 - 635, 2013/08

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

Cr is the representative material of multi-orbital antiferromagnetism. We numerically calculate the band structure and density of states in commensurate antiferromagnetic Cr by multi-orbital Hubbard model with mean-field approximation. The result is adopted to the calculation of optical conductivity. The spectra of the optical conductivity is consistent with experimental data, and this promises the validity of our model.

Journal Articles

Spin dynamics and resonant inelastic X-ray scattering in chromium with commensurate spin-density wave order

Sugimoto, Kodai*; Li, Z.*; Kaneshita, Eiji*; Tsutsui, Kenji; Toyama, Takami*

Physical Review B, 87(13), p.134418_1 - 134418_8, 2013/04

 Times Cited Count:5 Percentile:28.48(Materials Science, Multidisciplinary)

We theoretically investigate spin dynamics and L-edge resonant inelastic X-ray scattering (RIXS) of chromiumwith commensurate spin-density wave (SDW) order, based on a multiband Hubbard model. Obtaining the ground state with the SDW mean-field approximation, we calculate the dynamical spin susceptibility by using random-phase approximation. We find that a collectivespin-wave excitation hardly damps up to 0.6 eV. Above the energy, the excitation overlaps individual particle-hole excitations, leading to broad spectral weight.

Journal Articles

Theoretical study of resonant inelastic X-ray scattering spectrum in nickelates

Tsutsui, Kenji; Toyama, Takami*; Koshibae, Wataru*; Maekawa, Sadamichi

Journal of Physics; Conference Series, 400(3), p.032105_1 - 032105_4, 2012/12

 Times Cited Count:0 Percentile:0.03

The two-dimensional nickelate La$$_{2-x}$$Sr$$_x$$NiO$$_4$$ has received special attention as a reference system of high-$$T_c$$ cuprates. The undoped nickelate ($$x$$=0) has the charge-transfer gap in the optical conductivity. Upon doping of holes, a broad spectrum appears in the gap. We have shown theoretically that the broad spectrum comes from excitations to the low spin states. In the Ni $$K$$-edge resonant inelastic X-ray scattering (RIXS) measurement, the momentum-resolved charge excitations are obtained. In this study, we examine theoretically the RIXS spectra on nickelates by using numerically exact diagonalization techniques on the two-band Hubbard model. We also calculate other spectra such as the dynamical charge density function and discuss what excitations appear in the RIXS spectrum.

Journal Articles

Electronic excitations around the substituted atom in La$$_2$$Cu$$_{1-y}$$N$$_y$$O$$_4$$ as seen via resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji; Ikeuchi, Kazuhiko*; Jarrige, I.; Mizuki, Junichiro; Hiraka, Haruhiro*; Yamada, Kazuyoshi*; Toyama, Takami*; Maekawa, Sadamichi; Endo, Yasuo*; et al.

Physical Review B, 85(10), p.104509_1 - 104509_5, 2012/03

 Times Cited Count:3 Percentile:16.62(Materials Science, Multidisciplinary)

Journal Articles

Effect of B-site randomness on the antiferroelectric/relaxor nature of the ground state; Inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

Owada, Kenji; Fukuda, Tatsuo; Mizuki, Junichiro; Hirota, Kazuma*; Terauchi, Hikaru*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Owa, Hidehiro*; Yasuda, Naohiko*

Journal of the Korean Physical Society, 59(3), p.2509 - 2514, 2011/09

 Times Cited Count:2 Percentile:21.57(Physics, Multidisciplinary)

Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ (PIN) can be antiferroelectric (AFE), ferroelectric (FE) or a relaxor depending upon the perovskite B-site randomness. Orderd PIN (O-PIN, without B-site randomness) is supposed to be an ideal system of lead-based complex perovskite Pb(B'B'')O$$_{3}$$ and expected to give us a clear picture of the AFE/relaxor nature of the ground state by the B-site randomness. We studied the dynamics of O-PIN by inelastic X-ray scattering. The quasielastic (QE) scattering shows the critical slowing down and the transverse acoustic (TA) mode shows the softening towards $$T_{rm N}$$. On the other hand, the transverse optic (TO) mode shows the softening toward low temperature with no clear anomaly at $$T_{rm N}$$. These results represent that the antiferroelectric (AFE) phase transition is associated with the TA and the origin of the QE scattering, while ferroelectric correlation does exist behind the AFE ordering. The effect of B-site randomness is finally discussed on the basis of the results.

Journal Articles

Theory of resonant inelastic X-ray scattering spectrum for Ni impurities in cuprates

Tsutsui, Kenji; Toyama, Takami*; Maekawa, Sadamichi

Journal of Physics and Chemistry of Solids, 72(5), p.354 - 357, 2011/05

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

We carry out the numerically exact diagonalization on small clusters of the d-p model with a Ni impurity site to simulate a resonant inelastic X-ray scattering spectra, as well as the single-particle excitation ones. We propose the resonant inelastic X-ray scattering experiment for Ni K edge to confirm the hole binding around the Ni impurity.

Journal Articles

Theoretical study of resonant inelastic X-ray scattering spectrum in the Hubbard ladder

Tsutsui, Kenji; Toyama, Takami*; Maekawa, Sadamichi*

Physica C, 470(Suppl.1), p.S232 - S233, 2010/12

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

The spectra of the Cu $$K$$-edge Resonant inelastic X-ray scattering on the ladder cuprates are calculated by using the exact diagonalization method. So far it has been suggested that the momentum-dependence of the spectra on the ladder system is related with the formation of the spin singlet in the ground state. It has also revealed that the stabilization of the spin singlet strongly depends on the sign of the diagonal hopping of holes. In this study, in order to clarify the relationship between the spectra and the formation of the singlet state, the dependence of the spectra on the diagonal hopping of holes is examined. We find that the feature of the spectra is actually changed by the hopping and conclude that the resonant inelastic X-ray scattering can reveal the formation of the spin singlet state in the ladder system.

Journal Articles

Resonant inelastic X-ray scattering of La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$

Ishii, Kenji; Ikeuchi, Kazuhiko*; Jarrige, I.; Mizuki, Junichiro; Hiraka, Haruhiro*; Yamada, Kazuyoshi*; Tsutsui, Kenji; Toyama, Takami*; Maekawa, Sadamichi*; Endo, Yasuo*; et al.

Physica C, 470(Suppl.1), p.S155 - S157, 2010/12

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

Journal Articles

Temperature dependence of the electronic structure of Sr$$_{14}$$Cu$$_{24}$$O$$_{41}$$ studied by resonant inelastic X-ray scattering

Yoshida, Masahiro; Ishii, Kenji; Ikeuchi, Kazuhiko*; Jarrige, I.; Murakami, Yoichi*; Mizuki, Junichiro; Tsutsui, Kenji; Toyama, Takami*; Maekawa, Sadamichi*; Kudo, Kazutaka*; et al.

Physica C, 470(Suppl.1), p.S145 - S146, 2010/12

 Times Cited Count:4 Percentile:23.57(Physics, Applied)

Journal Articles

Ripple loss of alpha particles in a low-aspect ratio tokamak reactor

Tani, Keiji*; Nishio, Satoshi; Tobita, Kenji; Tsutsui, Hiroaki*; Mimata, Hideyuki*; Iio, Shunji*; Aoki, Takayuki*

Denki Gakkai Rombunshi, A, 129(9), p.569 - 574, 2009/09

Studies on the loss of fusion produced alpha particles enhanced by toroidal field (TF) ripple in a low-aspect-ratio tokamak reactor (VECTOR) have been made by using an orbit-following Monte-Carlo code. In actual TF coil systems, the ripple loss of alpha particles is strongly reduced as the aspect ratio becomes low (the power loss is proportional to A$$^{8.8}$$ for A more than 2.5) and the reduction of the number of TF coils results in a large amount of ripple losses even in a low-aspect-ratio tokamak.

Journal Articles

Numerical study of the ripple resonance diffusion of alpha particles in tokamaks

Mimata, Hideyuki*; Tani, Keiji*; Tsutsui, Hiroaki*; Tobita, Kenji; Iio, Shunji*; Shimada, Ryuichi*

Plasma and Fusion Research (Internet), 4, p.008_1 - 008_8, 2009/04

The energy dependence of the diffusion coefficients of alpha particles in rippled magnetic fields of tokamaks are numerically investigated with an orbit following Monte Carlo code. The diffusion coefficients are enhanced around the ripple resonance energy while they are reduced and has a minimum near the resonance energy, and hence they have an M-shaped dependence on the energy. The ripple resonance is caused by a radial change of the toroidal precession of banana particles, and creates islands in the phase space related with the toroidal and poloidal angles. Since the particles outside the separatrix mainly contribute to the diffusion, the M-shaped energy dependence is explained by both island structure and initial distribution of particles in the phase space. Such a ripple resonant diffusion is dominant for fusion-produced alpha particles in the slowing down process.

Journal Articles

Antiferroelectric correlation in relaxor Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ and ferroelectric correlation in antiferroelectric Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

Owada, Kenji; Hirota, Kazuma*; Terauchi, Hikaru*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro; Owa, Hidehiro*; Yasuda, Naohiko*

Transactions of the Materials Research Society of Japan, 34(1), p.19 - 22, 2009/03

Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ (PIN) can be antiferroelectric (AFE), ferroelectric (FE) or a relaxor depending upon the perovskite B-site randomness. This is characterized by measurements of dielectric response, which shows behavior that is usually clearly in one of those three classes. In contrast, X-ray scattering studies suggest the presence of AFE correlation in the relaxor state and FE in AFE state. Weak phonon softening at zone boundary in relaxor state shows that the AFE correlation intrinsically exists in PIN, as does the corresponding elastic scattering at (${it h}$/2 ${it k}$/2 0), while weak diffuse scattering around 333 Bragg reflection appears in AFE state suggesting FE correlation. These results will support our previous speculation that the AFE and FE correlations coexist in PIN (K. Owada ${it et al}$., Phys, Rev. B${bf 77}$ 094136 (2008)). Such a coexistence or competition is widely seen in the perovskite relaxor and the coexistence of FE and AFE correlations is essential for generating relaxor state.

Journal Articles

Exact diagonalization study on nonmagnetic impurity effects in high-$$T_{c}$$ superconductors

Tsutsui, Kenji; Toyama, Atsushi*; Toyama, Takami*; Maekawa, Sadamichi*

Journal of Physics and Chemistry of Solids, 69(12), p.3365 - 3368, 2008/12

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

Substitution of impurities Zn and Ni for Cu in high-$$T_{c}$$ superconductors has attracted much attention. The recent neutron scattering experiment show that Ni doping traps holes in the vicinity of Ni sites. We theoretically examine the electronic state with impurity based on the $$d-p$$ model where impurity Zn and Ni 3$$d$$ orbitals are explicitly treated. We carry out the numerically exact diagonalization method on small cluster. We find the region where a hole is trapped in the Ni site so that the effective hole concentration decreases and the ground state has strong antiferromagnetic correlations, as indicated from the experimental study.

Journal Articles

Momentum-resolved charge excitations in high-$$T$$$$_{rm c}$$ cuprates studied by resonant inelastic X-ray scattering

Ishii, Kenji; Hoesch, M.*; Inami, Toshiya; Kuzushita, Kaori*; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Mizuki, Junichiro; Endo, Yasuo; Tsutsui, Kenji*; et al.

Journal of Physics and Chemistry of Solids, 69(12), p.3118 - 3124, 2008/12

 Times Cited Count:3 Percentile:19.29(Chemistry, Multidisciplinary)

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