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Journal Articles

Polarization-analyzed resonant inelastic X-ray scattering of the orbital excitations in KCuF$$_3$$

Ishii, Kenji; Ishihara, Sumio*; Murakami, Yoichi*; Ikeuchi, Kazuhiko*; Kuzushita, Kaori*; Inami, Toshiya; Owada, Kenji; Yoshida, Masahiro; Jarrige, I.; Tatami, Naka*; et al.

Physical Review B, 83(24), p.241101_1 - 241101_4, 2011/06

 Times Cited Count:21 Percentile:64.41(Materials Science, Multidisciplinary)

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:18.13(Chemistry, Multidisciplinary)

Journal Articles

Resonant X-ray magnetic diffraction experiments on SmB$$_2$$C$$_2$$

Inami, Toshiya; Homma, Tetsuo*; Tsutsui, Satoshi*; Indo, Kentaro*; Onodera, Hideya*; Ishii, Kenji; Owada, Kenji; Kuzushita, Kaori*; Nakao, Hironori*; Murakami, Yoichi*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.748 - 750, 2007/03

We investigated successive phase transitions in SmB$$_2$$C$$_2$$ at $$T_{rm N2}$$=37K and $$T_{rm N1}$$=51K by means of resonant X-ray diffraction. Strong resonant diffraction signal is observed at the 101 reflection below $$T_{rm N2}$$ at the Sm $$L_3$$ edge, whereas in the intermediate phase signals appear at incommensurate positions $${vec Q}$$=(1$$pmdelta$$, $$pmdelta$$,1) where $$delta$$=0.13. Accordingly, the successive phase transitions in SmB$$_2$$C$$_2$$ is found to be commensurate-to-incommensurate magnetic phase transitions.

Journal Articles

Momentum dependence of Mott gap excitations in optimally doped YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ studied by resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Kuzushita, Kaori; Inami, Toshiya; Owada, Kenji; Maekawa, Sadamichi*; Masui, Takahiko*; Tajima, Setsuko*; et al.

AIP Conference Proceedings 850, p.445 - 446, 2006/09

Mott gap excitations in the optimally doped high-$$T_{c}$$ superconductor YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ ($$T_{c}$$ = 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the $$ab$$-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the $$b^{*}$$ direction, while the excitation from the CuO$$_2$$ plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO$$_2$$ plane site.

Journal Articles

Doping Momentum dependence of charge dynamics in Nd$$_{2-x}$$Ce$$_{x}$$CuO$$_4$$ (x=0, 0.075, and 0.15) studied by Resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Inami, Toshiya; Tsubota, Masami; Yamada, Kazuyoshi*; et al.

AIP Conference Proceedings 850, p.403 - 404, 2006/09

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high-$$T_{c}$$ superconductor Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with $${mathbf q}$$-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Articles

Resonant magnetic X-ray scattering study of UPd$$_2$$Al$$_3$$

Ishii, Kenji; Kuzushita, Kaori; Murakami, Yoichi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.102 - 104, 2006/08

UPd$$_2$$Al$$_3$$ is an attractive material because of the coexistence of the antiferromagnetic order below $$T_N$$ = 14.5 K and superconductivity below $$T_c$$ = 2 K. In order to discuss the coupling between magnetism and superconductivity by resonant magnetic X-ray scattering (RMXS), nature of the resonance at each absorption edge should be clarified before the measurements across $$T_c$$. Therefore we performed RMXS study from U $$M_1$$ to $$M_4$$ edge at $$T_c < T < T_N$$. In addition to a huge resonance at $$M_4$$-edge, we observed a resonant feature at $$M_2$$-edge which corresponds to the transition from $$3p_{1/2}$$ to $$6d$$ orbitals, while resonance at $$M_1$$-edge and $$M_3$$-edge is rather small.

Journal Articles

Induced orbital polarization of Ga ligand atoms in U$$T$$Ga$$_5$$ ($$T$$=Ni, Pd, and Pt)

Kuzushita, Kaori*; Ishii, Kenji; Wilkins, S. B.*; Janousova, B.*; Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Kaneko, Koji; Metoki, Naoto; et al.

Physical Review B, 73(10), p.104431_1 - 104431_5, 2006/03

 Times Cited Count:8 Percentile:38.44(Materials Science, Multidisciplinary)

We report a resonant X-ray scattering study of antiferromagnetic uranium compounds U$$T$$Ga$$_5$$ ($$T$$=Ni, Pd, and Pt) at the Ga $$K$$-edge. A large resonant signal is observed below the N$'e$el temperatures. The azimuth dependence in both $$pi$$-$$pi'$$ and $$pi$$-$$sigma'$$ polarization channels establishes that the resonant signal has the symmetry of the magnetic dipole. This resonance with the band electrons is interpreted within a semi-localized model as an orbital polarization of the Ga $$4p$$ states induced through strong hybridization with U $$5f$$ valence level. These results demonstrate that resonant magnetic X-ray scattering at the anions, taken in combination with symmetry arguments, can be used to determine the configuration of the U $$5f$$ moments and provide information about the hybridization.

Journal Articles

Electronic excitations in hole-doped La$$_{1-x}$$Sr$$_{x}$$MnO$$_{3}$$ studied by resonant inelastic X-ray scattering

Ishii, Kenji; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori; Mizuki, Junichiro; Murakami, Yoichi; Ishihara, Sumio*; Endo, Yasuo*; Maekawa, Sadamichi*; Hirota, Kazuma*; et al.

Journal of Physics and Chemistry of Solids, 66(12), p.2157 - 2162, 2005/12

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

We have studied electronic excitations of hole-doped manganese oxides La$$_{1-x}$$Sr$$_x$$MnO$$_3$$ ($$x=0.2$$ and $$0.4$$) by resonant inelastic X-ray scattering at Mn K absorption edge. We observed in the excitation spectra that the Mott gap of La$$_{0.6}$$Sr$$_{0.4}$$MnO$$_{3}$$ was filled by hole-doping. In La$$_{0.8}$$Sr$$_{0.2}$$MnO$$_{3}$$, which shows a metal-insulator transition, we found that temperature dependence of scattering intensity is different between two scattering vectors. It may reflects a anisotropic electronic structure which originates from the orbital degrees of freedom in manganese oxides.

Journal Articles

Momentum dependence of charge excitations in the electron-doped superconductor Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$; A Resonant inelastic X-ray scattering study

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Tsubota, Masami; Inami, Toshiya; Mizuki, Junichiro; et al.

Physical Review Letters, 94(20), p.207003_1 - 207003_4, 2005/05

 Times Cited Count:72 Percentile:89.21(Physics, Multidisciplinary)

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high-$$T_{c}$$ superconductor Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with $${mathbf q}$$-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Articles

Mott gap excitations in twin-free YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ ($$T_{c}$$ = 93 K) studied by resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Kuzushita, Kaori; Inami, Toshiya; Owada, Kenji; Maekawa, Sadamichi*; Masui, Takahiko*; Tajima, Setsuko*; et al.

Physical Review Letters, 94(18), p.187002_1 - 187002_4, 2005/05

 Times Cited Count:40 Percentile:80.93(Physics, Multidisciplinary)

Mott gap excitations in the optimally doped high-$$T_{c}$$ superconductor YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ ($$T_{c}$$ = 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the $$ab$$-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the $$b^{*}$$ direction, while the excitation from the CuO$$_2$$ plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO$$_2$$ plane site.

Journal Articles

Resonant X-ray scattering study of UNiGa$$_5$$

Kuzushita, Kaori; Ishii, Kenji; Owada, Kenji; Murakami, Yoichi; Kaneko, Koji; Metoki, Naoto; Lander, G. H.; Ikeda, Shugo; Haga, Yoshinori; Onuki, Yoshichika

Physica B; Condensed Matter, 359-361, p.1045 - 1047, 2005/04

 Times Cited Count:2 Percentile:11.66(Physics, Condensed Matter)

In UNiGa$$_5$$ which shows antiferromagnetic ordering below $textit{T$_N$}$ = 86 K with 0.75 $$mu_B$$/U, we observed resonant magnetic reflections using synchrotron X-ray tuned the incident photon energy near M$$_4$$-edge of U and K-edge of Ga, and the large enhancement about 10$$^2$$ at just resonant energy of Ga K-edge although Ga is a nonmagnetic element. It is considered that the origin of the magnetic resonant scattering intensity at Ga K-edge is the Ga-4$textit{p}$ orbital polarization induced by the 5$textit{f}$ orbital polarization at the neighboring U atom due to the hybridization.

Journal Articles

Resonant inelastic X-ray scattering study of the hole-doped manganites La$$_{1-x}$$Sr$$_x$$MnO$$_3$$ ($$x=0.2$$, $$0.4$$)

Ishii, Kenji; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori; Mizuki, Junichiro; Murakami, Yoichi; Ishihara, Sumio*; Endo, Yasuo*; Maekawa, Sadamichi*; Hirota, Kazuma*; et al.

Physical Review B, 70(22), p.224437_1 - 224437_6, 2004/12

 Times Cited Count:19 Percentile:64.32(Materials Science, Multidisciplinary)

Electronic excitations in the hole doped manganese oxides (La$$_{1-x}$$Sr$$_x$$MnO$$_3$$, $$x=0.2$$ and $$0.4$$) have been elucidated by using the resonant inelastic X-ray scattering (RIXS) method. A doping effect in the strongly correlated electron systems has been observed for the first time. The scattering spectra show that a salient peak appears in low energies indicating the persistence of the Mott gap. At the same time, the energy gap is partly filled by doping holes and the spectral weight energy shifts toward lower energies. The excitation spectra show little change in the momentum space as is in undoped LaMnO$$_3$$. On the other hand, the scattering intensities in the low energy excitations of $$x=0.2$$ are anisotropic in temperature dependence, which indicates an anisotropy of magnetic interaction and underlying effect of the orbital.

Journal Articles

Charge disproportionation and magnetic properties in perovskite iron oxides

Kuzushita, Kaori; Morimoto, Shotaro*; Nasu, Saburo*

Physica B; Condensed Matter, 329-333(1-4), p.736 - 737, 2003/05

 Times Cited Count:9 Percentile:45.98(Physics, Condensed Matter)

The physical properties of perovskite iron oxides are closely related to the network of FeO$$_6$$ octahedra. The charge disproportionation (2Fe$$^{4+}$$ $$rightarrow$$ Fe$$^{3+}$$ + Fe$$^{5+}$$), not observed in SrFeO$$_3$$, occurs in the oxides being cut the network of FeO$$_6$$ octahedra, for example, by introduction of Fe$$^{3+}$$ by substitution La for Sr and change in the dimension by insertion of SrO layer. When Co is substituted 40% of Fe in Sr$$_3$$Fe$$_2$$O$$_7$$, the magnetic order changes to ferromagnetic from antiferromagnetic and charge disproportionation is suppressed.

Oral presentation

Resonant inelastic X-ray scattering in strongly correlated electron systems

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

no journal, , 

Resonant inelastic X-ray scattering studies on high-$$T_c$$ superconductors Nd$$_{2-x}$$Ce$$_x$$CuO$$_4$$ and YBa$$_2$$Cu$$_3$$O$$_{6+x}$$ are presented. In Nd$$_2$$CuO$$_4$$ and YBa$$_2$$Cu$$_3$$O$$_6$$, which are Mott insulators, an excitation across the Mott gap is observed around 2 eV. The spectral weight of this excitation shifts to higher energy with increasing the momentum transfer and the dispersion of the excitation is larger along the $$[pi,pi]$$ direction than the $$[pi,0]$$ direction. An intraband excitation in the upper Hubbard band emerges in the spectra of electron-doped Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$. As a function of the momentum transfer in the CuO$$_2$$ plane, the excitation shifts to higher energy up to 2-2.5 eV at the zone boundary, accompanied by an increase of the spectral width. On the other hand, excitations from two inequivalent Cu sites in hole-doped YBa$$_2$$Cu$$_3$$O$$_7$$ are distinguished by the momentum dependence and the Mott gap of the CuO chain site is found to be much smaller than that of the CuO$$_2$$ plane site.

Oral presentation

Polarization dependence in RIXS of La$$_{1-x}$$Sr$$_x$$MnO$$_3$$

Ishii, Kenji; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori*; Mizuki, Junichiro; Murakami, Yoichi*; Ishihara, Sumio*; Endo, Yasuo*; Maekawa, Sadamichi*; Hirota, Kazuma*; et al.

no journal, , 

no abstracts in English

Oral presentation

Polarization-analyzed RIXS for orbital excitation in KCuF$$_3$$

Ishii, Kenji; Ishihara, Sumio*; Murakami, Yoichi*; Ikeuchi, Kazuhiko*; Kuzushita, Kaori*; Owada, Kenji; Inami, Toshiya; Yoshida, Masahiro; Jarrige, I.; Tatami, Naka*; et al.

no journal, , 

no abstracts in English

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