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Yoshimoto, Masahiro; Ueno, Tomoaki; Togashi, Tomohito; Takeda, Osamu; Kanazawa, Kenichiro; Watanabe, Masao; Yamazaki, Yoshio; Kamiya, Junichiro; Takayanagi, Tomohiro; Kuramochi, Masaya; et al.
IEEE Transactions on Applied Superconductivity, 18(2), p.297 - 300, 2008/06
Times Cited Count：4 Percentile：30.89(Engineering, Electrical & Electronic)
edge in NiOTakahashi, Manabu*; Igarashi, Junichi*; Nomura, Takuji
Physical Review B, 75(23), p.235113_1 - 235113_9, 2007/06
Times Cited Count：18 Percentile：60.66(Materials Science, Multidisciplinary)Resonant inelastic X-ray scattering at the edge in NiO is analyzed theoretically. The antiferromagnetic groud state is described by the Hartree-Fock approximation, the core-hole potential is treated within the Born approximation, and the electron correlation effect is considered within the random-phase approximation. Consequently, the observed spectral shape and its dependence on the momentum transfer of scattered photons are explained quantitatively.
Nomura, Takuji; Igarashi, Junichi*; Takahashi, Manabu*
Hoshako, 20(3), p.171 - 179, 2007/05
Recently, electronic excitation spectra have been observed in strongly correlated electron systems such as transition-metal compounds, by utilizing the highly brilliant synchrotron radiation. Among them, momentum dependent excitation spectra are observed in resonant inelastic X-ray scattering (RIXS) experiments at the transition-metal absorption -edge in the hard X-ray regime. The microscopic theory of RIXS constructed recently by the present authors is explained. An essential point is that RIXS spectrum is closely related to the dynamical density correlation function of correlated transition-metal 
electrons. Spectral shapes and momentum dependence observed in several transition-metaloxides are semiquantitatively explained.
Watanabe, Masao; Irie, Yoshiro; Kamiya, Junichiro; Shimada, Taihei; Takayanagi, Tomohiro; Fujimori, Hiroshi*; Igarashi, Susumu*; Kawakubo, Toshimichi*; Nakayama, Hisayoshi*
IEEE Transactions on Applied Superconductivity, 16(2), p.1350 - 1353, 2006/06
Times Cited Count：2 Percentile：18.89(Engineering, Electrical & Electronic)Thick septa are used in the injection and extraction section of the 3 GeV rapid cycling synchrotron of the J-PARC. We have been designing seven thick septum magnets, two for injection, two for beam dump and three for extraction, respectively. These septa require low-loss operations. For the mechanical stability they are operated by direct current. The yoke is made of the soft-iron block. We have been designing them by using the three-dimensional magnet static field calculation code, TOSCA. In this presentation, we discuss about magnetic field flatness in the gap and effects of the leakage fields in the synchrotron.
CuO
Nomura, Takuji; Igarashi, Junichi*
Physical Review B, 71(3), p.035110_1 - 035110_5, 2005/01
Times Cited Count：47 Percentile：82.48(Materials Science, Multidisciplinary)The experimental result of resonant inelastic X-ray scattering in LaCuO is theoretically analyzed. The ground state of the system is described within the Hartree-Fock approximation, and the electronic excitation processes are taken account of within the random phase approximation. In the experiment, the spectral shape shows a strong dependence on the transferred momentum of the photon. We have succeeded in reproducing theoretically this dependence quantitatively.
edge of Si; Theoretical analysisNishikawa, Yunori; Usuda, Manabu; Igarashi, Junichi*
Journal of the Physical Society of Japan, 73(11), p.3171 - 3176, 2004/11
Times Cited Count：3 Percentile：26.46(Physics, Multidisciplinary)no abstracts in English
Nomura, Takuji; Igarashi, Junichi*
Journal of the Physical Society of Japan, 73(7), p.1677 - 1680, 2004/07
Times Cited Count：26 Percentile：73.65(Physics, Multidisciplinary)We study theoretically the resonant inelastic X-ray scattering in quasi-one-dimensional insulating copper oxides, where the incident photon energy is tuned to the Cu1
-4
absorption energy. Our attention is focused particularly on the strong momentum-transfer dependence of the spectral shape observed in recent experiments. We describe the antiferromagnetic ground state within the Hartree-Fock theory, and consider charge excitations from the ground state within the random phase approximation. By taking account of the electron correlation effects perturbatively, we obtain detailed momentum-transfer dependence of the spectra in a semiquantitative agreement with the experiments.
edge in UGa
; A Band theoretical approachUsuda, Manabu; Igarashi, Junichi*; Kodama, Akio*
Physical Review B, 69(22), p.224402_1 - 224402_5, 2004/06
Times Cited Count：20 Percentile：65.76(Materials Science, Multidisciplinary)Magnetic resonant X-ray scattering (MRXS) at the edge of Ga in an antiferromagnetic phase of UGa is studied on the basis of a band-structure calculation. We find that a relatively large orbital polarization in the unoccupied states of the Ga 
band is induced by the 
orbital polarizations at neighboring U atoms through the Ga and U hybridization, and thereby leading to the large MRXS intensity.
Nishikawa, Yunori; Usuda, Manabu; Igarashi, Junichi*; Shoji, Hironobu*; Iwazumi, Toshiaki*
Journal of the Physical Society of Japan, 73(4), p.970 - 975, 2004/04
Times Cited Count：6 Percentile：41.19(Physics, Multidisciplinary)no abstracts in English
CNagao, Tatsuya*; Igarashi, Junichi
Physica B; Condensed Matter, 345(1-4), p.70 - 73, 2004/03
Times Cited Count：1 Percentile：7.12(Physics, Condensed Matter)To investigate the effect of the lattice distortion on the resonant X-ray scattering (RXS) spectra in DyBC, we study the crystal electric field Hamiltonian to fit the low-lying level scheme. By using the quasi-quartet ground states of the Hamiltonian, we analyze the cooperative Jahn-Teller effect at absolute zero. We find that a certain type of buckling of sheets of B and C atoms is an energetically favored state. This naturally leads to a canted quadrupole ordering phase consistent with the experiment. We show that the obtained lattice distortion gives rise to large intensities on RXS spectra around the Dy L
edge by modulating 5d bands.
calculation of magnetic resonant X-ray scattering spectra in NiOUsuda, Manabu; Takahashi, Manabu*; Igarashi, Junichi
Physical Review B, 69(1), p.014408_1 - 014408_7, 2004/01
Times Cited Count：11 Percentile：49.52(Materials Science, Multidisciplinary)We have investigated the magnetic X-ray scattering spectra around the edge of Ni in antiferromagnetic NiO on the basis of an calculation. By taking account of orbital polarization through the spin-orbit interaction, we reproduce well the spectra obtained experimentally. We have analyzed the contributions of the resonant dipolar, quadrupolar, and non-resonant scattering processes and clarified the mechanism of the resonant magnetic X-ray scattering.
Nagao, Tatsuya*; Igarashi, Junichi
Journal of the Physical Society of Japan, 72(9), p.2381 - 2384, 2003/09
Times Cited Count：10 Percentile：55.03(Physics, Multidisciplinary)We examine the mechanism of the X-ray diffraction process by including the Thomson scattering (TS) term in addition to the resonant X-ray scattering (RXS) term near the Ce L absorption edge in the antiferroquadrupole (AFQ) ordering phase of CeB. Assuming the AFQ order in the 4f states but without any lattice distortion, we obtain the TS intensity comparable to the RXS intensity, owing to the anisotropic charge distribution of 4f states. The present calculation reproduces well the interference pattern between the TS and RXS terms for the (5/2,3/2,3/2) spot observed in the recent experiment. The result suggests that the TS signal as well as the main peak of the RXS signal are a direct reflection of the AFQ order in CeB.
edge of Mn
GaCTakahashi, Manabu*; Igarashi, Junichi
Physical Review B, 67(24), p.245104_1 - 245104_5, 2003/06
Times Cited Count：23 Percentile：70.62(Materials Science, Multidisciplinary)We theoretically investigate the origin of the X-ray magnetic circular dichroism (XMCD) spectra at the K edge of Mn and Ga in the ferromagnetic phase of MnGaC on the basis of an ab initio calculation. Taking account of the spin-orbit interaction in the LDA scheme, we obtain the XMCD spectra in excellent agreement with the recent experiment. We have analyzed the origin of each structure, and thus elucidated the mechanism of inducing the orbital polarization in the p symmetric states. We also discuss a simple sum rule connecting the XMCD spectra with the orbital moment in the p symmetric states.
CIgarashi, Junichi; Nagao, Tatsuya*
Journal of the Physical Society of Japan, 72(5), p.1279 - 1286, 2003/05
Times Cited Count：13 Percentile：61.11(Physics, Multidisciplinary)We study the resonant X-ray scattering (RXS) spectra at the Dy L_
absorption edge in the quadrupolar ordering phase of DyBC. Analyzing the buckling of sheets of B and C atoms, we construct an effective model that the crystal field is acting on the 5d and 4f states with the principal axes different for different sublattices. Treating the 5d states as a band and the 4f states as localized states, we calculate the spectra within the dipole transition. We take account of processes that (1) the lattice distorion directly modulates the 5d states and (2) the charge anisotropy of the quadrupole ordering 4f states modulates the 5d states through the 5d-4f Coulomb interaction. The former process is found to give dominant contribution to the spectra.
Takahashi, Manabu*; Igarashi, Junichi
Physica B; Condensed Matter, 329-333(Part2), p.870 - 871, 2003/05
Times Cited Count：2 Percentile：15.16(Physics, Condensed Matter)We study the resonant X-ray scattering (RXS) spectra around the Cu K edge in KCuF on the basis of the band structure calculation combined with the LDA+U approximation. The lattice distortion is introduced as inputs of the calculation. We reproduce well the experimental spectra as a function of photon energy around the main--K--edge (MKE). The spectral structure around the MKE is independent of the magnetic order (MO) and the orbital order (OO) but strongly dependent on the magnitude of the Jahn--Teller distortion (JTD).
CNagao, Tatsuya*; Igarashi, Junichi
Physica B; Condensed Matter, 329-333(Part2), p.628 - 630, 2003/05
Times Cited Count：5 Percentile：31.44(Physics, Condensed Matter)For elucidating the relation between the resonant X-ray scattering (RXS) signal and the orbital order, we calculate the RXS spectra near the Dy L absorption edge in DyBC, in the antiferro-quadrupole (AFQ) ordering phase. Using a microscopic model that the 4f states of Dy are atomic while the 5d states form an energy band with a reasonable density of states, we obtain sufficient RXS intensities on the AFQ superlattice spot assuming the quadrupole order in the 4f states but without any lattice distortion, in good agreement with the recent experiment. The present result demonstrates the mechanism that the intensity is brought about by the modulation of 5d states through the anisotropic term of the 5d-4f Coulomb interaction.
Takahashi, Manabu*; Usuda, Manabu; Igarashi, Junichi
Physical Review B, 67(6), p.064425_1 - 064425_7, 2003/02
Times Cited Count：21 Percentile：68.23(Materials Science, Multidisciplinary)We study the magnetic resonant X-ray scattering (RXS) spectra around the K edge of Cu in KCuF on the basis of an ab initio calculation. We use the full-potential linearlized augumented plane wave method in the LDA+U scheme, and introduce the lattice distortion as inputs of the calculation. We obtain finite intensity on magnetic superlattice spots by taking account of the spin-orbit interaction. We also calculate the RXS intensity on orbital superlattice spots. It is found that the intensity increases with increasing Jahn-Teller distortion.
Igarashi, Junichi; Nagao, Tatsuya*
Journal of the Physical Society of Japan, 71(7), p.1771 - 1779, 2002/07
Times Cited Count：15 Percentile：63.88(Physics, Multidisciplinary)no abstracts in English
