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Journal Articles

Repetition Rate Multiplication: RRM, an advanced measuring method planed for the backscattering instrument, ${it DNA}$ at the MLF, J-PARC

Takahashi, Nobuaki; Shibata, Kaoru; Kawakita, Yukinobu; Nakajima, Kenji; Inamura, Yasuhiro; Nakatani, Takeshi; Nakagawa, Hiroshi; Fujiwara, Satoru; Sato, Taku*; Tsukushi, Itaru*; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB007_1 - SB007_4, 2011/12

 Times Cited Count:5 Percentile:41.54(Physics, Multidisciplinary)

Journal Articles

Orbital ordering in low-moment ground-state of parent compounds in iron-based superconductors

Machida, Masahiko; Nakamura, Hiroki

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB022_1 - SB022_4, 2011/12

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

Since the discovery of the iron-based superconductor, a large discrepancy between experimental observations and first-principles calculations in the magnetic moment of the antiferromagnetic state of the parent compounds has been intensively debated. The observed moment values are about 3 to 5 times smaller than those of the calculation although there is a variety of the difference depending on the materials. Very recently, an interesting calculation data fully reproducing the observed low moment has been suggested by F. Cricchio et al., who performed first-principles calculations using a LDA+U scheme. In this study, we suggest that the new state is a possible candidate to well explain the other data, e.g., strong anisotropy in spatial patterns measured by STM and magnetic excitations found by neutron scattering. Furthermore, we compare the result with other theoretical works reproducing similar low moment in terms of orbital ordering.

Journal Articles

First-principles study of hydrogen-doping effects on iron-based superconductors

Nakamura, Hiroki; Machida, Masahiko

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB009_1 - SB009_4, 2011/12

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

Since the discovery of the iron-based superconductor, LaFeAsO$$_{1-x}$$F$$_x$$ whose Tc reached 26K, various types of iron-based superconductors have been fabricated to attain higher Tc. Recently, it is reported that Tc of an iron-based superconductor LaFeAsO$$_{1-y}$$ is enhanced to 35K by doping hydrogen. This result implies that atoms of light elements penetrate into the crystal of iron-based superconductors and transform their structures into more useful ones for superconductivity. In this paper, we investigate how the hydrogen atoms are doped in the iron-based superconductors by using the first-principles density functional theory. Furthermore, we evaluate the effects of doping on the crystal structures and electronic states and explore the origin of the Tc enhancements.

Journal Articles

Theoretical analysis for inelastic neutron scattering on BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ using realistic three-dimensional 10-orbital tight-binding model

Nagai, Yuki; Nakamura, Hiroki; Suzuki, Katsuhiro*; Usui, Hidetomo*; Kuroki, Kazuhiko*; Machida, Masahiko

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB021_1 - SB021_4, 2011/12

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

We calculate spin susceptibility on the basis of the multi-orbital random-phase approximation with use of the realistic three-dimensional 10-orbital tight-binding model for an iron-based superconductor BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ which seems to have gap-nodes. We show that the shape of nodes on the Fermi surface for BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ is distinguishable according to inelastic neutron scattering experiments. Our results are consistent with the recent neutron scattering experiments for BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ with Tc = 30 K.

Journal Articles

AMATERAS; A Cold-neutron disk chopper spectrometer

Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Kajimoto, Ryoichi; Inamura, Yasuhiro; Takahashi, Nobuaki; Aizawa, Kazuya; Suzuya, Kentaro; Shibata, Kaoru; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB028_1 - SB028_6, 2011/05

 Times Cited Count:90 Percentile:94.38(Physics, Multidisciplinary)

AMATERAS is a cold-neutron disk-chopper spectrometer in MLF, J-PARC. The construction of main part of the spectrometer has been completed in spring of 2009. Soon after that, we have started the commissioning work on AMATERAS. The performance of AMATERAS has been examined by test experiments in the course of commissioning. In parallel to these works, we have started the user program on AMATERAS from December 2009 and we are getting scientific results from our spectrometer. In this presentation, we will report the current status of AMATERAS including the results of performance tests and some of examples of scientific outputs.

Journal Articles

Phonon spectra of PrFeAsO$$_{1-y}$$ via inelastic X-ray scattering

Fukuda, Tatsuo; Baron, A. Q. R.*; Nakamura, Hiroki; Shamoto, Shinichi; Ishikado, Motoyuki; Machida, Masahiko; Uchiyama, Hiroshi*; Iyo, Akira*; Kito, Hijiri*; Mizuki, Junichiro; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB015_1 - SB015_4, 2011/01

 Times Cited Count:1 Percentile:12.07(Physics, Multidisciplinary)

We have investigated phonons of PrFeAsO$$_{1-y}$$ using high-resolution inelastic X-ray scattering and $$ab-initio$$ calculations. Extensive measurements show that there are some changes in phonon spectra with temperature and/or doping. However, we compare our data with several calculations and find that the experimentally observed changes are much smaller than differences between the experiment. data and the calculations. Agreement is improved if magnetism is included in the calculations. However, still in disagreement even in the parent sample below T$$_N$$. We consider several modifications of the $$ab-initio$$ calculations. The best agreement is obtained from modifying the nonmagnetic calculation. by softening only the in-plane nearest-neighbor Fe-As force constant. Fluctuating magnetism may be a partial explanation for the failure of the calculations, but seems incomplete in the face of the similarity of the measured phonon response in all the systems investigated including those known to have static magnetism.

Journal Articles

The Fermi chopper spectrometer 4SEASONS at J-PARC

Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Nakajima, Kenji; Kawamura, Seiko; Yokoo, Tetsuya*; Nakatani, Takeshi; Maruyama, Ryuji; Soyama, Kazuhiko; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB025_1 - SB025_6, 2011/01

 Times Cited Count:71 Percentile:92.29(Physics, Multidisciplinary)

Oral presentation

Numerical study on the spin dynamics of the Kagome lattice antiferromagnet

Sakai, Toru

no journal, , 

The Kagome lattice antiferromagnet is one of interesting frustrated spin systems. Particularly since several candidate materials of the S=1/2 quantum Kagome lattice antiferromagnet were synthesized, the experimental and theoretical studies have been accelerated very much. However, the spin dynamics of the Kagome lattice antiferromagnet is still unclear, although the neutron scattering, nuclear spin resonance, electron spin resonance etc. have already been performed for those materials. In order to solve the spin dynamics theoretically, we investigated some anisotropic Kagome lattice by the numerical diagonalization of finite-size clusters. As a result, a mechanism of the double peak structure in the temperature dependence of the specific heat was clarified. In addition we found an interesting field induced phenomenon, so called the magnetization ramp. We also calculate the dynamical spin correlation to compare with the neutron scattering experiment.

Oral presentation

Role of excess oxygens in cuprates

Mori, Michiyasu

no journal, , 

Oral presentation

Structural analyses on iron-based superconductors PrFeAsO$$_{1-y}$$ and PrFeAsO$$_{1-x}$$F$$_x$$

Kodama, Katsuaki; Ishikado, Motoyuki; Esaka, Fumitaka; Iyo, Akira*; Eisaki, Hiroshi*; Shamoto, Shinichi

no journal, , 

Oral presentation

Electronic excitations by resonant inelastic X-ray scattering

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

no journal, , 

Oral presentation

Effect of magnetic field in non-centrosymmetric heavy-fermion superconductor CePt$$_3$$Si

Kaneko, Koji; Stockert, O.*; Skoulatos, M.*; Schneidewind, A.*; Takeuchi, Tetsuya*; Matsuda, Tatsuma; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika; Metoki, Naoto

no journal, , 

Oral presentation

Inelastic neutron scattering studies on iron-based high-$$T_c$$ superconductors

Ishikado, Motoyuki; Kodama, Katsuaki; Wakimoto, Shuichi; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

Among various iron-based superconductors, we have systematically studied on LaFeAsO$$_{1-x}$$F$$_x$$ ($$T_c^{max}$$=28 K) and BaFe$$_2$$(As,P)$$_2$$ ($$T_c^{max}$$=31 K) by the Fermi chopper spectrometer 4SEASONS (J-PARC). We will discuss the possible relation between high-$$T_c$$ superconductivity and magnetic fluctuation based on our inelastic neutron scattering results.

Oral presentation

AMATERAS; Cold-neutron disk-chopper spectrometer

Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Kajimoto, Ryoichi; Inamura, Yasuhiro; Takahashi, Nobuaki; Aizawa, Kazuya; Suzuya, Kentaro; Shibata, Kaoru; et al.

no journal, , 

14 (Records 1-14 displayed on this page)
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