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Journal Articles

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite; $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance studies

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ueda, Hiroaki*; Tanioku, Yasuaki*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Takao, Kenta*; Shimoda, Aiko*; et al.

Physical Review B, 98(6), p.064403_1 - 064403_10, 2018/08

 Times Cited Count:6 Percentile:45.58(Materials Science, Multidisciplinary)

To specify preferential occupation sites of Co substituents and to clarify charge and spin states of Co ions in (La, Co)-cosubstituted hexagonal magnetoplumbite-type (M-type) Sr ferrite, $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance (NMR) spectra are measured under zero and external magnetic fields using powdered and single crystalline specimens. To a considerable degree, the charge compensation between La$$^{3+}$$ and Co$$^{2+}$$ works in the equal (La, Co)-codoped case, where more than half of the Co ions are considered to be present in the minority spin $$4f_1$$ sites at the center of the oxygen tetrahedra, with the $$S$$ = 3/2 state carrying a small orbital moment owing to spin-orbit interaction. The remaining small number of high-spin Co$$^{2+}$$ ($$S$$ = 3/2, $$L$$ = 1) ions with unquenched orbital moments would be distributed to the other octahedral $$12k$$, $$2a$$, and $$4f_2$$ sites.

Journal Articles

NMR investigation of spin fluctuations in the itinerant-electron magnetic compound $${rm Sr}_{1-x}{rm Ca}_x{rm Co}_2{rm P}_2$$

Imai, Masaki; Michioka, Chishiro*; Ueda, Hiroaki*; Yoshimura, Kazuyoshi*

Physical Review B, 95(5), p.054417_1 - 054414_7, 2017/02

 Times Cited Count:2 Percentile:15.91(Materials Science, Multidisciplinary)

We took $$^{31}$$P NMR measurements of mainly paramagnetic phase $${rm Sr}_{1-x}{rm Ca}_x{rm Co}_2{rm P}_2$$ to reveal the itinerant-electron metamagnetic transition, and of its magnetically ordered phase, and characterized their spin fluctuations by estimating the spin fluctuation parameter $$T_{0}$$ corresponding to the width of the spin fluctuation in the spectrum in frequency space. As $$x$$ increases from 0 to 0.5, the in-plane component of $$T_{0}$$ decreases proportionally with the metamagnetic transition field. In the antiferromagnetic cT phase, $$T_{0}$$ is constant and spin fluctuations show an isotropic character in contrast to their behavior in the paramagnetic ucT phase. These results indicate that the in-plane spin fluctuations due to the quasi-two-dimensional crystal structure play a significant role in the metamagnetic transition of this system.

Journal Articles

Spin-orbit fluctuations in frustrated heavy-fermion metal LiV$$_{2}$$O$$_{4}$$

Tomiyasu, Keisuke*; Iwasa, Kazuaki*; Ueda, Hiroaki*; Niitaka, Seiji*; Takagi, Hidenori*; Kawamura, Seiko; Kikuchi, Tatsuya; Inamura, Yasuhiro; Nakajima, Kenji; Yamada, Kazuyoshi*

Physical Review Letters, 113(23), p.236402_1 - 236402_5, 2014/12

 Times Cited Count:13 Percentile:68.3(Physics, Multidisciplinary)

Spin fluctuations were studied over a wide momentum ($$hbar$$$$Q$$) and energy ($$E$$) space in the frustrated ${it d}$-electron heavy-fermion metal LiV$$_{2}$$O$$_{4}$$ by time-of-flight inelastic neutron scattering. We observed the overall ${it Q-E}$ evolutions near the characteristic ${it Q}$ = 0.6 $AA $^{-1}$$ peak and found another weak broad magnetic peak around 2.4 $AA $^{-1}$$. The data are described by a simple response function, a partially delocalized magnetic form factor, and antiferromagnetic short-range spatial correlations, indicating that heavy-fermion formation is attributable to spin-orbit fluctuations with orbital hybridization.

JAEA Reports

Development of safety management system for works in radiation controlled area (Joint research)

Hiyama, Kazuhisa; Hanawa, Nobuhiro; Kurosawa, Akihiko; Eguchi, Shohei; Hori, Naohiko; Kusunoki, Tsuyoshi; Ueda, Hisao; Shimada, Hiroshi; Kanda, Hiroaki*; Saito, Isamu*

JAEA-Technology 2013-045, 32 Pages, 2014/02

JAEA-Technology-2013-045.pdf:5.83MB

This report summarizes regarding to develop of real-time multifunctional access control system which is able to manage worker's access control and exposure dose at real-time in the reactor building, besides worker's location and worker might be fall down by accident.

Journal Articles

In-vessel tritium

Ueda, Yoshio*; Oya, Kaoru*; Ashikawa, Naoko*; Ito, Atsushi*; Ono, Tadayoshi*; Kato, Daiji*; Kawashima, Hisato; Kawamura, Gakushi*; Kenmotsu, Takahiro*; Saito, Seiki*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 88(9), p.484 - 502, 2012/09

no abstracts in English

Journal Articles

Relaxation dynamics of photocarrieres in one-dimensional Mott insulators coupled to phonons

Matsueda, Hiroaki*; Sota, Shigetoshi*; Toyama, Takami*; Maekawa, Sadamichi

Journal of the Physical Society of Japan, 81(1), p.013701_1 - 013701_4, 2012/01

 Times Cited Count:36 Percentile:84.19(Physics, Multidisciplinary)

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

Universal magnetic structure of the half-magnetization phase in Cr-based spinels

Matsuda, Masaaki; Oyama, Kenji*; Yoshii, Shunsuke*; Nojiri, Hiroyuki*; Frings, P.*; Duc, F.*; Vignolle, B.*; Rikken, G. L. J. A.*; Regnault, L.-P.*; Lee, S.-H.*; et al.

Physical Review Letters, 104(4), p.047201_1 - 047201_4, 2010/01

 Times Cited Count:23 Percentile:75.81(Physics, Multidisciplinary)

Journal Articles

Plasma physics and radiation hydrodynamics in developing an extreme ultraviolet light source for lithography

Nishihara, Katsunobu*; Sunahara, Atsushi*; Sasaki, Akira; Nunami, Masanori*; Tanuma, Hajime*; Fujioka, Shinsuke*; Shimada, Yoshinori*; Fujima, Kazumi*; Furukawa, Hiroyuki*; Kato, Takako*; et al.

Physics of Plasmas, 15(5), p.056708_1 - 056708_11, 2008/00

 Times Cited Count:106 Percentile:97.57(Physics, Fluids & Plasmas)

Journal Articles

Spin-lattice instability to a fractional magnetization state in the spinel HgCr$$_{2}$$O$$_{4}$$

Matsuda, Masaaki; Ueda, Hiroaki*; Kikkawa, Akiko*; Tanaka, Yoshikazu*; Katsumata, Koichi*; Narumi, Yasuo*; Inami, Toshiya; Ueda, Yutaka*; Lee, S.-H.*

Nature Physics, 3(6), p.397 - 400, 2007/06

 Times Cited Count:92 Percentile:93.17(Physics, Multidisciplinary)

Cr-CrCr-based spinel compounds ACr$$_{2}$$O$$_{4}$$ (A=Mg, Zn, Cd, and Hg) are so far the best model systems for a network of corner-sharing tetrahedrons with isotropic nearest-neighbor antiferromagnetic interactions. The systems exhibit novel spin-Peierls phase transitions from cubic spin liquid to non-cubic N$'e$el states at low temperatures. Recent bulk magnetization studies on CdCr$$_{2}$$O$$_{4}$$ and HgCr$$_{2}$$O$$_{4}$$ revealed the magnetic field-induced half magnetization plateau states that are stable over a wide range of field. Recent bulk magnetization studies on CdCr$$_{2}$$O$$_{4}$$ and HgCr$$_{2}$$O$$_{4}$$ revealed the magnetic field-induced half magnetization plateau states that are stable over a wide range of field.

Journal Articles

Spiral spin structure in the Heisenberg pyrochlore magnet CdCr$$_2$$O$$_4$$

Matsuda, Masaaki; Takeda, Masayasu; Nakamura, Mitsutaka; Kakurai, Kazuhisa; Osawa, Akira*; Leli$`e$vre-Berna, E.*; Chung, J.-H.*; Ueda, Hiroaki*; Takagi, Hidenori*; Lee, S.-H.*

Physical Review B, 75(10), p.104415_1 - 104415_6, 2007/03

 Times Cited Count:41 Percentile:82.49(Materials Science, Multidisciplinary)

A frustrated spinel CdCr$$_2$$O$$_4$$ undergoes a three-dimensional spin-Peierls transition at $$T_N$$ = 7.8 K from a cubic paramagnetic to a tetragonal N$'e$el state. The N$'e$el state has a spiral magnetic structure with a characteristic wave vector of $$(0,delta,1)$$ when the $$c$$ axis elongated. Here we report our spherical neutron polarimetry experiments to investigate the spiral spin structure in detail. Our results indicate that the spins lie in the $$ac$$ plane perpendicular to the direction of the spiral modulation. We also found that the spiral structure in the $$ac$$ plane is elliptical with the $$c$$-component larger by $$sim$$24% than the $$a$$-component, suggesting a strong coupling between the magnetic structure and structural distortion. Unpolarized neutron diffraction under an external magnetic field has also been performed. The magnetic field dependence suggests existence of magnetic anisotropy in the N$'e$el state, which is consistent with our previous inelastic studies.

Journal Articles

Low-density tin targets for efficient extreme ultraviolet light emission from laser-produced plasmas

Okuno, Tomoharu*; Fujioka, Shinsuke*; Nishimura, Hiroaki*; Tao, Y.*; Nagai, Keiji*; Gu, Q.*; Ueda, Nobuyoshi*; Ando, Tsuyoshi*; Nishihara, Katsunobu*; Norimatsu, Takayoshi*; et al.

Applied Physics Letters, 88(16), p.161501_1 - 161501_3, 2006/04

 Times Cited Count:63 Percentile:88.67(Physics, Applied)

no abstracts in English

Journal Articles

Quest for the high-filed phase of CdCr$$_2$$O$$_4$$ using an X-ray diffraction technique

Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Murata, Yuto*; Matsuda, Yasuhiro*; Nojiri, Hiroyuki*; Ueda, Hiroaki*; Murakami, Yoichi*

Journal of Physics; Conference Series, 51, p.502 - 505, 2006/00

 Times Cited Count:15 Percentile:97.63

no abstracts in English

Journal Articles

Opacity effect on extreme ultraviolet radiation from laser-produced tin plasmas

Fujioka, Shinsuke*; Nishimura, Hiroaki*; Nishihara, Katsunobu*; Sasaki, Akira; Sunahara, Atsushi*; Okuno, Tomoharu*; Ueda, Nobuyoshi*; Ando, Tsuyoshi*; Tao, Y.*; Shimada, Yoshinori*; et al.

Physical Review Letters, 95(23), p.235004_1 - 235004_4, 2005/12

 Times Cited Count:135 Percentile:95.53(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Statics and dynamics of incommensurate spin order in a geometrically frustrated antiferromagnet CdCr$$_2$$O$$_4$$

Chung, J.-H.*; Matsuda, Masaaki; Lee, S.-H.*; Kakurai, Kazuhisa; Ueda, Hiroaki*; Sato, Taku*; Takagi, Hidenori*; Hong, K.-P.*; Park, S.*

Physical Review Letters, 95(24), p.247204_1 - 247204_4, 2005/12

 Times Cited Count:133 Percentile:95.33(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Neutron scattering investigation on quantum spin system SrCu$$_{2}$$(BO$$_{3}$$)$$_{2}$$

Kakurai, Kazuhisa; Nukui, Katsuyuki*; Aso, Naofumi*; Nishi, Masakazu*; Kadowaki, Hiroaki*; Kageyama, Hiroshi*; Ueda, Yutaka*; Regnault, L.-P.*; C$'e$pas, O.*

Progress of Theoretical Physics Supplement, (159), p.22 - 32, 2005/10

no abstracts in English

Journal Articles

High energy-resolution inelastic neutron scattering experiments on triplet bound state excitations in SrCu$$_{2}$$(BO$$_{3}$$)$$_{2}$$

Aso, Naofumi*; Kageyama, Hiroshi*; Nukui, Katsuyuki*; Nishi, Masakazu*; Kadowaki, Hiroaki*; Ueda, Yutaka*; Kakurai, Kazuhisa

Journal of the Physical Society of Japan, 74(8), p.2189 - 2192, 2005/08

 Times Cited Count:7 Percentile:46.33(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Single crystal growth and fermi surface properties of an antiferromagnet UPdGa$$_5$$

Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Yamamoto, Etsuji; Nakashima, Miho*; Kirita, Shingo*; Kobayashi, Tatsuo*; Hedo, Masato*; Uwatoko, Yoshiya*; Yamagami, Hiroshi*; et al.

Journal of the Physical Society of Japan, 74(8), p.2277 - 2281, 2005/08

 Times Cited Count:10 Percentile:54.78(Physics, Multidisciplinary)

We have succeeded in growing a high-quality single crystal of an antiferromagnet UPdGa$$_5$$ by the Ga-flux method with the off-stoichiometric composition of U : Pd : Ga = 1 : 2 : 7.3. The electronic state has been investigated by the de Haas-van Alphen experiment, indicating the similar cylindrical Fermi surfaces as in an antiferromagnet UPtGa$$_5$$. We have also studied the pressure effect by measuring the electrical resistivity. The N$$acute{rm e}$$el temperature decreases with increasing pressure and becomes zero at 3.1 GPa. The antiferromagnetic state is changed into the paramagnetic state above 3.1 GPa.

Journal Articles

Relativistic laser plasma from micron-sized argon clusters as a debris-free X-ray source for pulse X-ray diffraction

Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki; Nakai, Yoshiki*; Tsuji, Koichi*; Yamakawa, Koichi; Hironaka, Yoichiro*; Kishimura, Hiroaki*; et al.

Applied Physics Letters, 85(21), p.5099 - 5101, 2004/11

 Times Cited Count:10 Percentile:41.51(Physics, Applied)

We have demonstrated diffraction from Si(111) crystal using X-rays from highly ionized Ar ions produced by laser irradiation with an intensity of 6$$times$$10$$^{18}$$ W/cm$$^{2}$$ and a pulse duration of 30 fs acting upon micron-sized Ar clusters. The measured total photon flux and line width in the He$$_{alpha1}$$ line (3.14 keV) were 4$$times$$10$$^{7}$$ photons/shot/4$$pi$$sr and 3.7 eV (FWHM), respectively, which is sufficient to utilize as a debris-free light source for time-resolved X-ray diffraction studies.

Journal Articles

$$s$$-process branching at $$^{185}$$W revised

Mohr, P.*; Shizuma, Toshiyuki; Ueda, Hiroyasu*; Goko, Shinji*; Makinaga, Ayano*; Hara, Kaoru*; Hayakawa, Takehito; Lui, Y.-W.*; Ogaki, Hideaki*; Utsunomiya, Hiroaki*

Physical Review C, 69(3), p.032801_1 - 032801_4, 2004/03

 Times Cited Count:31 Percentile:83.47(Physics, Nuclear)

The neutron capture cross section of the unstable s-process branching nucleus $$^{185}$$W has been derived from experimental data of the inverse $$^{186}$$W($$gamma$$,n)$$^{185}$$W photodisintegration taken with monochromatic photon beams from laser Compton scattering. The result of $$sigma = 553 pm 60$$mb at $$kT = 30$$keV leads to a relatively high effective neutron density in the classical s process of $$N_{rm{n}} = 4.7 times 10^8,{rm{cm}}^{-3}$$. A realistic model for the s process in thermally pulsing AGB stars overestimates the abundance of $$^{186}$$Os significantly because of the relatively small neutron capture cross section of $$^{185}$$W.

36 (Records 1-20 displayed on this page)