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Nakajima, Kenji; Kawamura, Seiko; Kofu, Maiko; Murai, Naoki; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Wakai, Daisuke*
JPS Conference Proceedings (Internet), 33, p.011089_1 - 011089_7, 2021/03
The recent update of AMATERAS, a cold-neutron disk-chopper spectrometer at Japan Proton Accelerator Research Complex (J-PARC), is reported. AMATERAS has been operating for a decade. Since 2017, some updates have been done or are underway, which include installing new detectors, replacing the vacuum system of the scattering chamber, and other works. We are also working on the re-investigation of the resolution function. Demonstration measurements were carried out at 1MW test operations done in 2018 and 2019. Plans of upgrading the spectrometer are currently being considered.
=0 long-range magnetic order in centennialite CaCu
(OD)
Cl
0.6DO; A Spin-
perfect kagome antiferromagnet with 
-
-
Iida, Kazuki*; Yoshida, Hiroyuki*; Nakao, Akiko*; Jeschke, H. O.*; Iqbal, Y.*; Nakajima, Kenji; Kawamura, Seiko; Munakata, Koji*; Inamura, Yasuhiro; Murai, Naoki; et al.
Physical Review B, 101(22), p.220408_1 - 220408_6, 2020/06
Times Cited Count：6 Percentile：75.71(Materials Science, Multidisciplinary)Crystal and magnetic structures of the mineral centennialite CaCu(OD)Cl 0.6DO are investigated by means of synchrotron X-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. In CaCu(OD)Cl 0.6DO, Cu
ions form a geometrically perfect kagome network with antiferromagnetic . No intersite disorder between Cu and Ca ions is detected. CaCu(OD)Cl 0.6DO enters a magnetic long-range ordered state below 
= 7.2 K, and the =0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)
B. Our DFT calculations indicate the presence of antiferromagnetic and ferromagnetic superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin- PFFRG analysis shows a dominance of =0 type magnetic correlations, consistent with and indicating proximity to the observed =0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a -- kagome antiferromagnet.
RuO
proved by spin resonanceIida, Kazuki*; Kofu, Maiko; Suzuki, Katsuhiro*; Murai, Naoki; Kawamura, Seiko; Kajimoto, Ryoichi; Inamura, Yasuhiro; Ishikado, Motoyuki*; Hasegawa, Shunsuke*; Masuda, Takatsugu*; et al.
Journal of the Physical Society of Japan, 89(5), p.053702_1 - 053702_5, 2020/05
Times Cited Count：8 Percentile：87.06(Physics, Multidisciplinary)Murai, Naoki; Fukuda, Tatsuo; Nakajima, Masamichi*; Kawamura, Mitsuaki*; Ishikawa, Daisuke*; Tajima, Setsuko*; Baron, A. Q. R.*
Physical Review B, 101(3), p.035126_1 - 035126_6, 2020/01
Times Cited Count：2 Percentile：44.66(Materials Science, Multidisciplinary)We report an inelastic X-ray scattering investigation of phonons in FeSe superconductor. Comparing the experimental phonon dispersion with density functional theory (DFT) calculations in the non-magnetic state, we found a significant disagreement between them. A better overall agreement was obtained by allowing for spin-polarization in DFT calculations, despite the absence of magnetic order in FeSe. This calculation gives a realistic approximation, at DFT level, of the disordered paramagnetic state of FeSe, in which strong spin fluctuations are present.
K
FeAsIdeta, Shinichiro*; Murai, Naoki; Nakajima, Masamichi*; Kajimoto, Ryoichi; Tanaka, Kiyohisa*
Physical Review B, 100(23), p.235135_1 - 235135_7, 2019/12
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)Kajimoto, Ryoichi; Ishikado, Motoyuki*; Kira, Hiroshi*; Kaneko, Koji; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Inamura, Yasuhiro; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Murai, Naoki; et al.
Physica B; Condensed Matter, 556, p.26 - 30, 2019/03
Times Cited Count：2 Percentile：22.21(Physics, Condensed Matter)
MoO
( = In, Sc)Iida, Kazuki*; Yoshida, Hiroyuki*; Okabe, Hirotaka*; Katayama, Naoyuki*; Ishii, Yuto*; Koda, Akihiro*; Inamura, Yasuhiro; Murai, Naoki; Ishikado, Motoyuki*; Kadono, Ryosuke*; et al.
Scientific Reports (Internet), 9(1), p.1826_1 - 1826_9, 2019/02
Times Cited Count：5 Percentile：62.37(Multidisciplinary Sciences)Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Ishikado, Motoyuki*; Murai, Naoki; Kira, Hiroshi*; Nakatani, Takeshi; et al.
Journal of Physics; Conference Series, 1021(1), p.012030_1 - 012030_6, 2018/06
Times Cited Count：3 Percentile：95.16
K
FeAs as seen via time-of-flight inelastic neutron scatteringMurai, Naoki; Suzuki, Katsuhiro*; Ideta, Shinichiro*; Nakajima, Masamichi*; Tanaka, Kiyohisa*; Ikeda, Hiroaki*; Kajimoto, Ryoichi
Physical Review B, 97(24), p.241112_1 - 241112_6, 2018/06
Times Cited Count：5 Percentile：39.54(Materials Science, Multidisciplinary)We use inelastic neutron scattering (INS) to investigate the effect of electron correlations on spin dynamics in iron-based superconductor BaKFeAs. Our INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A first principles analysis of dynamical spin susceptibility, incorporating the mass renormalization factor of 3, as determined by angle-resolved photoemission spectroscopy, provides a reasonable description of the observed spin excitations. This analysis shows that electron correlations in the Fe-3d bands yield enhanced effective electron masses, and consequently, induce substantial narrowing of the spin excitation bandwidth. Our results highlight the importance of electron correlations in an itinerant description of the spin excitations in iron-based superconductors.
studied by neutron scattering and their relation with thermal conductivitiesKajimoto, Ryoichi; Nakamura, Mitsutaka; Murai, Naoki; Shamoto, Shinichi; Honda, Takashi*; Ikeda, Kazutaka*; Otomo, Toshiya*; Hata, Hiroto*; Eto, Takahiro*; Noda, Masaaki*; et al.
Scientific Reports (Internet), 8(1), p.9651_1 - 9651_8, 2018/06
Times Cited Count：4 Percentile：32.16(Multidisciplinary Sciences)
AsIida, Kazuki*; Ishikado, Motoyuki*; Nagai, Yuki; Yoshida, Hiroyuki*; Christianson, A. D.*; Murai, Naoki; Kawashima, Kenji*; Yoshida, Yoshiyuki*; Eisaki, Hiroshi*; Iyo, Akira*
Journal of the Physical Society of Japan, 86(9), p.093703_1 - 093703_4, 2017/09
Times Cited Count：19 Percentile：82.96(Physics, Multidisciplinary)As using high-resolution inelastic X-ray scatteringMurai, Naoki*; Fukuda, Tatsuo; Kobayashi, Tatsuya*; Nakajima, Masamichi*; Uchiyama, Hiroshi*; Ishikawa, Daisuke*; Tsutsui, Satoshi*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.
Physical Review B, 93(2), p.020301_1 - 020301_5, 2016/01
Times Cited Count：7 Percentile：41.71(Materials Science, Multidisciplinary)As via inelastic X-ray scatteringMurai, Naoki*; Fukuda, Tatsuo; Uchiyama, Hiroshi*; Tsutsui, Satoshi*; Ishikawa, Daisuke*; Kobayashi, Tatsuya*; Nakamura, Hiroki; Machida, Masahiko; Nakajima, Masamichi*; Miyasaka, Shigeki*; et al.
no journal, ,
no abstracts in English
Co
)As by inelastic X-ray scatteringMurai, Naoki*; Fukuda, Tatsuo; Nakajima, Masamichi*; Kobayashi, Tatsuya*; Uchiyama, Hiroshi*; Tsutsui, Satoshi*; Ishikawa, Daisuke*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.
no journal, ,
As via high-resolution inelastic X-ray scatteringMurai, Naoki; Fukuda, Tatsuo; Kobayashi, Tatsuya*; Nakajima, Masamichi*; Uchiyama, Hiroshi*; Ishikawa, Daisuke*; Tsutsui, Satoshi*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.
no journal, ,
We report the first IXS study of single crystals of SrFeAs that have been detwinned via application of in-plane uniaxial stress. Our results clearly show anisotropy in phonon structure below 
= 
characterized by mode splitting at tetragonally-equivalent momentum transfers. To the best of our knowledge, this is the first observation of phonon anisotropy in iron-pnictides at finite momentum transfers. We obtain good agreement with our results using calculations that are modified to account for a reduced magnetic moment and fluctuating magnetism. Previous efforts using either non-magnetic calculations or static magnetism tend to either get the dispersion wrong from non-magnetic calculations or strongly over-estimate the phonon mode splitting when static magnetism is included. Our model for the response below incorporates a phenomenological reduction in force constant anisotropy, by about 65%, that can be attributed to residual fast magnetic fluctuations. Above , all fluctuations are assumed to be fast and the response becomes the average of the results from the static magnetism. This serves as a starting point for a general model of phonons in iron-pnictides applicable to both non-magnetic and magnetic phases.
K_
Fe_
As_ (x = 0.25) as seen via inelastic neutron scatteringMurai, Naoki; Kajimoto, Ryoichi; Ikeuchi, Kazuhiko*; Tanaka, Kiyohisa*; Nakajima, Masamichi*; Ideta, Shinichiro*; Suzuki, Katsuhiro*
no journal, ,
We report an inelastic neutron scattering (INS) study of underdoped Ba_K_Fe_As_ that shows the presence of double-resonance at the same commensurate wave vector in the superconducting (SC) state. By comparing our INS data with the SC gap structure of the same crystal, as measured by angle-resolved photoemission spectroscopy (ARPES), we show that the observed double-resonance feature originates neither from SC gap anisotropy nor from multiple SC gaps on different Fermi-surface sheets. This suggests that the double-resonance feature in iron-pnictides cannot be interpreted within a spin-exciton scenario.
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Ishikado, Motoyuki*; Murai, Naoki; Nakatani, Takeshi; Kubo, Naoya*; et al.
no journal, ,
no abstracts in English
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Inamura, Yasuhiro; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Ishikado, Motoyuki*; Murai, Naoki
no journal, ,
KFeAs due to electron correlation effectsMurai, Naoki; Kajimoto, Ryoichi; Suzuki, Katsuhiro*; Ideta, Shinichiro*; Nakajima, Masamichi*; Ikeda, Hiroaki*; Tanaka, Kiyohisa*
no journal, ,
Using inelastic neutron scattering (INS) and angle-resolved photoemission spectroscopy (ARPES), we investigate the spin dynamics of iron-based superconductor BaKFeAs. The INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A random phase approximation (RPA) treatment of the dynamical spin susceptibility, incorporating the band renormalization factor of 3 derived from the ARPES measurements on the same crystals, provides a reasonable description of the observed spin excitations. This analysis shows that the experimental spin excitation peak lies at a much lower energy than the bare value, reflecting a strong renormalization of the quasiparticle band dispersion near the Fermi level due to electron correlation effect. The present results point to a unified framework that connects the magnetic response to the underlying electronic structure of the materials.
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Inamura, Yasuhiro; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Ishikado, Motoyuki*; Murai, Naoki
no journal, ,
no abstracts in English
