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=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：29 Percentile：79.18(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.
Yasuda, Satoshi; Tamura, Kazuhisa; Terasawa, Tomoo; Yano, Masahiro; Nakajima, Hideaki*; Morimoto, Takahiro*; Okazaki, Toshiya*; Agari, Ryushi*; Takahashi, Yasufumi*; Kato, Masaru*; et al.
Journal of Physical Chemistry C, 124(9), p.5300 - 5307, 2020/03
Times Cited Count：18 Percentile：55.99(Chemistry, Physical)Confinement of hydrogen molecules at graphene-substrate interface has presented significant importance from the viewpoints of development of fundamental understanding of two-dimensional material interface and energy storage system. In this study, we investigate H confinement at a graphene-Au interface by combining selective proton permeability of graphene and the electrochemical hydrogen evolution reaction (electrochemical HER) method. After HER on a graphene/Au electrode in protonic acidic solution, scanning tunneling microscopy finds that H nanobubble structures can be produced between graphene and the Au surface. Strain analysis by Raman spectroscopy also shows that atomic size roughness on the graphene/Au surface originating from the HER-induced strain relaxation of graphene plays significant role in formation of the nucleation site and H storage capacity.
Nakajima, Taro*; Inamura, Yasuhiro; Ito, Takayoshi*; Oishi, Kazuki*; Oike, Hiroshi*; Kagawa, Fumitaka*; Kikkawa, Akiko*; Taguchi, Yasujiro*; Kakurai, Kazuhisa*; Tokura, Yoshinori*; et al.
Physical Review B, 98(1), p.014424_1 - 014424_5, 2018/07
Times Cited Count：9 Percentile：36.31(Materials Science, Multidisciplinary)We investigated the phase-transition kinetics of magnetic skyrmion lattice (SkL) in MnSi by means of stroboscopic small-angle neutron scattering (SANS). Temporal evolutions of SANS patterns were measured with time resolution of 13 ms while sweeping temperature as fast as 50 Ks
. It turned out that the paramagnetic-to-SkL transition immediately occurs upon traversing the equilibrium phase boundary on the rapid cooling, whereas the SkL-to-conical transition can be kinetically avoided to realize the low-temperature metastable SkL with a long-range magnetic order. The formation of the metastable SkL was found to be strongly dependent not only on cooling rate, but also on magnetic eld and trajectory in the H-T phase diagram.
CoSbO
Ito, Saya*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Kawamura, Seiko; Nakajima, Kenji; Ito, Shinichi*; Kuwahara, Keitaro*; Kakurai, Kazuhisa*
Nature Communications (Internet), 8, p.235_1 - 235_6, 2017/08
Times Cited Count：98 Percentile：94.70(Multidisciplinary Sciences)
O
by dynamical Jahn-Teller effectKamazawa, Kazuya*; Ishikado, Motoyuki*; Kawamura, Seiko; Kawakita, Yukinobu; Kakurai, Kazuhisa*; Nakajima, Kenji; Sato, Masashi*
Physical Review B, 95(10), p.104413_1 - 104413_7, 2017/03
Times Cited Count：2 Percentile：10.00(Materials Science, Multidisciplinary)Kajimoto, Ryoichi; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Kakurai, Kazuhisa; Hokazono, Takahisa*; Ozono, Akira*; Okuda, Tetsuji*
Journal of the Physical Society of Japan, 82(5), p.054702_1 - 054702_6, 2013/05
Times Cited Count：5 Percentile：37.34(Physics, Multidisciplinary)
Ga
O (
= 0, 0.018)Nakajima, Taro*; Mitsuda, Setsuo*; Takahashi, Keiichiro*; Yoshitomi, Keisuke*; Masuda, Kazuya*; Kaneko, Chikafumi*; Homma, Yuki*; Kobayashi, Satoru*; Kitazawa, Hideaki*; Kosaka, Masashi*; et al.
Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09
Times Cited Count：16 Percentile：64.45(Physics, Multidisciplinary)GaO (x =0, 0.018)Nakajima, Taro*; Mitsuda, Setsuo*; Takahashi, Keiichiro*; Yoshitomi, Keisuke*; Masuda, Kazuya*; Kaneko, Chikafumi*; Homma, Yuki*; Kobayashi, Satoru*; Kitazawa, Hideaki*; Kosaka, Masashi*; et al.
Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09
O
(
= Nb, Ta)Kawamura, Seiko; Nakajima, Kenji; Inamura, Yasuhiro; Tsujimoto, Yoshihiro*; Kitada, Atsushi*; Takeiri, Fumitaka*; Kageyama, Hiroshi*; Ajiro, Yoshitami*; Nishi, Masakazu*; Kakurai, Kazuhisa
Journal of Physics; Conference Series, 320, p.012037_1 - 012037_5, 2011/09
Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)The magnetic ground state of (CuCl)LaNb
O has been suggested to be a spin-singlet state with an excitation gap of 
meV, while (CuCl)LaTaO has an antiferromagnetic (AFM) ground state. The systems are suspected to be a frustrated quantum spin system due to the competition between the nearest and next-nearest exchange interactions. We have studied magnetic excitation in these systems by ToF inelastic neutron scattering technique. The measurements were performed on powder samples of (CuCl)LaNbO and (CuCl)LaTaO at a disk-chopper-type spectrometer AMATERAS in J-PARC. In both systems, a band-like excitation was observed at 
meV. The 
dependence of the intensity of magnetic excitation around 2 meV for (CuCl)LaNbO well reproduces that observed at a triple-axis spectrometer, exhibiting characteristics of spin-singlet dimers. On the other hand, (CuCl)LaTaO in the AFM state exhibits a different dependence.
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：146 Percentile：96.03(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.
studied by inelastic neutron scatteringKajimoto, Ryoichi; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Kakurai, Kazuhisa; Arai, Masatoshi; Hokazono, Takahisa*; Ozono, Akira*; Okuda, Tetsuji*
Journal of the Physical Society of Japan, 79(12), p.123705_1 - 123705_4, 2010/12
Times Cited Count：21 Percentile：70.48(Physics, Multidisciplinary)
Ga
OTerada, Noriki*; Nakajima, Taro*; Mitsuda, Setsuo*; Matsuda, Masaaki; Kakurai, Kazuhisa; Tanaka, Yoshihito*; Kitazawa, Hideaki*
Journal of Physics; Conference Series, 211(1), p.012005_1 - 012005_6, 2010/01
Times Cited Count：2 Percentile：65.38(Physics, Applied)Bobbili, S. R.*; Naik, P. A.*; Arora, V.*; Singhal, H.*; Chakravarty, U.*; Khan, R. A.*; Gupta, P. D.*; Nakajima, Kazuhisa*; Kameshima, Takashi
IEEE Transactions on Plasma Science, 36(4), p.1694 - 1698, 2008/08
Initial experiments on electron acceleration in self-modulatedlaser wake-field acceleration regime have been carried out at the Raja Ramanna Centre for Advanced Technology, Indore, India, using a 6 TW 45 fs Ti:sapphire laser. The laserbeam was focused to an intensity 
W/cm
on a supersonic helium gas jet. Total charge and spatial profile of the electron beam produced were measured using an integrating current transformer and a phosphor screen, respectively. For a plasma density of 
cm
, electron beam was produced with a high charge of 
nC/shot and a divergence of 
mrad.
Kotaki, Hideyuki; Daito, Izuru; Kando, Masaki; Hayashi, Yukio; Ma, J.-L.; Chen, L.-M.; Esirkepov, T. Z.; Fukuda, Yuji; Homma, Takayuki; Pirozhkov, A. S.; et al.
IEEE Transactions on Plasma Science, 36(4), p.1760 - 1764, 2008/08
Times Cited Count：10 Percentile：36.62(Physics, Fluids & Plasmas)The counter-crossing injection, which is a realistic setup for applications, by two sub-relativistic laser pulses colliding is demonstrated in sub-relativistic intensity laser pulse interaction with plasma. The laser pulses in plasma are self-focused to higher intensity when the laser power is above the threshold of a relativistic self-focusing. The collision of self-focused laser pulses generates a high-quality electron beam with high repeatability. The generated monoenergetic electron beam has 14 MeV of the peak energy, 11% of the energy spread, 22 pC of the charge, 1.6
mm mrad of the normalized emittance, and 50% of the repeatability.
Kameshima, Takashi; Hong, W.*; Sugiyama, Kiyohiro*; Wen, X.*; Wu, Y.*; Tang, C.*; Zhu, Q.*; Gu, Y.*; Zhang, B.*; Peng, H. S.*; et al.
Applied Physics Express, 1(6), p.066001_1 - 066001_3, 2008/05
A high-quality electron beam with a central energy of 0.56 GeV, an energy spread of 1.2 % rms, and a divergence of 0.59 mrad rms was produced by means of a 4cm ablative-capillary-discharge plasma channel driven by a 3.8 J 27 fs laser pulse. This is the first demonstration of electron acceleration with an ablative capillary discharge where in the capillary is stably operated in vacuum with a simple systemtriggered by a laser pulse. This result of the generation of a high-quality beam provides the prospects to realize a practical accelerator based on laser-plasma acceleration.
Kotaki, Hideyuki; Daito, Izuru; Hayashi, Yukio; Ma, J.-L.; Chen, L.-M.; Kando, Masaki; Esirkepov, T. Z.; Fukuda, Yuji; Homma, Takayuki; Pirozhkov, A. S.; et al.
Journal of Physics; Conference Series, 112(4), p.042031_1 - 042031_4, 2008/00
Times Cited Count：1 Percentile：54.32(Physics, Fluids & Plasmas)Laser-driven plasma accelerators have been conceived to be the next-generation particle accelerators, promising ultrahigh field particle acceleration with a very short duration electron beam. In the case of electron beam generation by using one laser pulse via wavebreaking, however, it is not stable. In order to generate a stable high-quality electron beam, optical injection by collision of two laser pulses is proposed. Recently, the electron generation with this approach was demonstrated. The experiment was carried out by the perfect head-on collision, which has problems to the backward laser light and the extraction of the generated electron beam. The counter-crossing injection, which is a realistic setup for applications, by two sub-relativistic laser pulses collision with the colliding angle of 45
is demonstrated. The collision of two laser pulses generates a high-quality electron beam with high repeatability. The generated monoenergetic electron beam has 14.4 MeV of the peak energy, 10.6% of the energy spread, 21.8 pC of the charge, 1.6 mm mrad of the normalized emittance, and 47.4% of the repeatability.
Chen, L.-M.; Nakajima, Kazuhisa; Hong, W.*; Hua, J. F.*; Kameshima, Takashi; Kotaki, Hideyuki; Sugiyama, Kiyohiro*; Wen, X.*; Wu, Y.*; Tang, C.*; et al.
Chinese Optics Letters, 5(S1), p.S133 - S135, 2007/05
Chen, L.-M.; Kotaki, Hideyuki; Nakajima, Kazuhisa*; Koga, J. K.; Bulanov, S. V.; Tajima, Toshiki; Gu, Y. Q.*; Peng, H. S.*; Wang, X. X.*; Wen, T. S.*; et al.
Physics of Plasmas, 14(4), p.040703_1 - 040703_4, 2007/04
Times Cited Count：38 Percentile：75.21(Physics, Fluids & Plasmas)An experiment for the laser self-guiding studies has been carried out with 100 TW laser pulse interaction with the long underdense plasma. Formation of extremely long plasma channel with its length, about 10 mm, 20 times above the Rayleigh length is observed. The self-focusing channel features such as the laser pulse significant bending and the electron cavity formation are demonstrated experimentally for the first time.
Nakajima, Kenji; Nakamura, Mitsutaka; Kajimoto, Ryoichi; Osakabe, Toyotaka; Kakurai, Kazuhisa; Matsuda, Masaaki; Metoki, Naoto; Wakimoto, Shuichi; Sato, Taku*; Ito, Shinichi*; et al.
Journal of Neutron Research, 15(1), p.13 - 21, 2007/03
no abstracts in English
Kotaki, Hideyuki; Oishi, Yuji*; Nayuki, Takuya*; Fujii, Takashi*; Nemoto, Koshichi*; Nakajima, Kazuhisa
Review of Scientific Instruments, 78(3), p.036102_1 - 036102_3, 2007/03
Times Cited Count：0 Percentile：0.00(Instruments & Instrumentation)no abstracts in English
