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Journal Articles

Rapid analysis of $$^{90}$$Sr in cattle bone and tooth samples by inductively coupled plasma mass spectrometry

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Terashima, Motoki; Fujiwara, Kenso; Kino, Yasushi*; Oka, Toshitaka; Takahashi, Atsushi*; Suzuki, Toshihiko*; et al.

Journal of Analytical Atomic Spectrometry, 36(8), p.1678 - 1682, 2021/08

 Times Cited Count:0 Percentile:0.02(Chemistry, Analytical)

Rapid analysis of $$^{90}$$Sr in bone and tooth samples of cattle were achieved by an inductively coupled plasma mass spectrometry (ICP-MS) coupled with mass shift and solid phase extraction techniques. Limit of detection (LOD) in the ICP-MS measurement of 0.1 g samples was lower than that of the radioactivity measurement. Analytical time of the ICP-MS method was reduced from 20 days to 11 hours, compared with the radiometric method. Therefore, the ICP-MS method can be rapid and useful procedure of $$^{90}$$Sr in small bone and tooth samples derived from terrestrial animals.

JAEA Reports

Development of solid-phase extraction technique for ICP-MS analysis of iodine-129 in environmental samples; Comparative study of anion-exchange and silver ion-supported resins on isolation of Iodine-129 from interference elements

Aoki, Jo; Matsueda, Makoto; Koarai, Kazuma; Terashima, Motoki; Fujiwara, Kenso; Abe, Hironobu

JAEA-Research 2021-002, 20 Pages, 2021/05

JAEA-Research-2021-002.pdf:2.75MB

In order to analyze extremely low concentrations of $$^{129}$$I in environmental samples by ICP-MS with high sensitivity and rapidity, it is necessary to remove interfering elements (Na, Mg, K, Ca, Mo, Cd and In) using a pretreatment method with Solid-phase Extraction Resin. Anion Exchange Resins with amino groups have been widely used as Solid-phase Extraction Resins, while Ag+ Supported Resins have also been widely used in recent years. It is necessary to optimize the pretreatment technique based on characteristics of the resins. In this study, we compared in terms of separation of I from matrix elements (Na, Mg, K, Ca, Mo, Cd and In) for DOWEX1-X8, AG 1-X8 and CL Resin, and investigated their suitability for ICP-MS analysis of $$^{129}$$I in environmental samples. The results of adsorption and elution experiments showed that all resins examined uptake and elute I quantitatively. CL Resin showed the highest removal performance of interfering elements, with 3.1% of Mo remaining, but other interfering elements were removed below the detection limit of ICP-MS. However, the Mo remained after the CL Resin treatment could interfere the ICP-MS measurement of $$^{129}$$I, based on the consideration of ratio of $$^{129}$$I and Mo. The eluate from CL Resin was treated with a Cation exchange resin (DOWEX 50WX8). As a result, Mo in the eluate was removed by up to 98% and the interference from Mo was reduced to measurable level. Therefore, the pretreatment method using CL Resin in combination with DOWEX 50WX8 is effective for ICP-MS analysis of $$^{129}$$I at extremely low concentrations (background level).

Journal Articles

Applicability of Sr resin for ICP-MS measurement of $$^{90}$$Sr in hard tissue samples

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Fujiwara, Kenso; Terashima, Motoki; Kitamura, Akihiro; Abe, Hironobu

KEK Proceedings 2020-4, p.180 - 185, 2020/11

Strontium-90 and $$^{90}$$Y, its daughter nuclide, adverse effects on the bone marrow. Monitoring of $$^{90}$$Sr in the bones have been required after the Fukushima-Daiichi Nuclear Power Plant accident. However, conventional radioactivity measurement method for $$^{90}$$Sr requires a complicated separation of $$^{90}$$Y and a time-consuming measurement. ICP-MS system has been applied to $$^{90}$$Sr concentration survey of water, soil, and edible part of fish. We applied the ICP-MS system for the bones for the first time. In this study, reference bone (JSAC 0785 fish bone) was used as measurement samples. Sample preparation of the bone was performed using a microwave digestion instrument. After sample preparation, $$^{90}$$Sr was determined using ICP-MS system with cascade separation steps based on on-line column separation and oxygen reaction. Strontium-90 in the bones was successfully separated from Ca, Ba, Y, Zr, Fe, Se, and Ge, which interfered in ICP-MS measurement, in the separation steps.

Journal Articles

Quasi-one-dimensional magnetic interactions and conduction electrons in EuCu$$_5$$ and EuAu$$_5$$ with the characteristic hexagonal structure

Matsuda, Shinya*; Ota, Joji*; Nakaima, Kenri*; Iha, Wataru*; Gochi, Jun*; Uwatoko, Yoshiya*; Nakashima, Miho*; Amako, Yasushi*; Honda, Fuminori*; Aoki, Dai*; et al.

Philosophical Magazine, 100(10), p.1244 - 1257, 2020/04

 Times Cited Count:2 Percentile:45.37(Materials Science, Multidisciplinary)

Journal Articles

Highlight of recent sample environment at J-PARC MLF

Kawamura, Seiko; Hattori, Takanori; Harjo, S.; Ikeda, Kazutaka*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Watanabe, Masao; Sakaguchi, Yoshifumi*; Oku, Takayuki

Neutron News, 30(1), p.11 - 13, 2019/05

In Japanese neutron scattering facilities, some SE equipment that are frequently used at an instrument, such as the closed-cycle refrigerator (CCR), have been prepared for the instrument as standard SE. They are operated for user experiments by the instrument group. The advantage of this practice is that they can optimize the design of the SE for the instrument and can directly respond to users' requests. On the other hand, the SE team in the Materials and Life Science Experimental Facility (MLF) in J-PARC has managed commonly used SE to allow neutron experiments with more advanced SE. In this report, recent SE in the MLF is introduced. Highlighted are the SE in BL11, BL19, BL21 and BL17 and other SE recently progressed by the SE team.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

 Times Cited Count:25 Percentile:72.31(Astronomy & Astrophysics)

We report on the event structure and double helicity asymmetry ($$A_{LL}$$) of jet production in longitudinally polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured $$A_{LL}$$ = -0.0014 $$pm$$ 0.0037 at the lowest $$P_T$$ bin and -0.0181 $$pm$$ 0.0282 at the highest $$P_T$$ bin. The measured $$A_{LL}$$ is compared with the predictions that assume various $$Delta G(x)$$ distributions.

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:156 Percentile:99.42(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Journal Articles

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

 Times Cited Count:8 Percentile:52.71(Physics, Nuclear)

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled $$p+p$$ collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to $$p+p$$ collisions.

Journal Articles

Measurement of neutral mesons in $$p$$ + $$p$$ collisions at $$sqrt{s}$$ = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

 Times Cited Count:149 Percentile:98.49(Astronomy & Astrophysics)

The PHENIX experiment at RHIC has measured the invariant differential cross section for production of $$K^0_s$$, $$omega$$, $$eta'$$ and $$phi$$ mesons in $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, $$n$$ and $$T$$, determining the high $$p_T$$ and characterizing the low $$p_T$$ regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

Journal Articles

Long-term behaviors of a tuunel in a sedimentary soft rock due to fluid-mechanical interaction

Aoki, Tomoyuki*; Sanada, Hiroyuki; Jo, Mayumi*; Yamamoto, Takuya*; Matsui, Hiroya

Dai-12-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.709 - 716, 2008/09

Long-term behaviors of a tunnel at great depth in sedimentary soft rocks are investigated based on pore fluid-mechanical interaction. Poroelastic parameters of diatomaceous and siliceous mudstones at the Horonobe URL site are determined from the tests proposed in this study using a triaxial test apparatus. The test procedures with their theoretical base are described. Coupled fluid-mechanical behaviors on circular and horse-shoe-shaped tunnels supported with shotcrete are numerically analyzed based on the theory of poroelasticity. Some long-term behaviors of rocks and supports peculiar to the fluid-mechanical interaction differing from creep behavior are found from the analysis results.

JAEA Reports

Study on investigation of microbial effects for geological disposal, 2 (Joint research)

Tochigi, Yoshikatsu; Yoshikawa, Hideki; Aoki, Kazuhiro; Yui, Mikazu; Asano, Takahiro*; Honjo, Hideko*; Haginuma, Masashi*; Kawakami, Yasushi*; Suzuki, Kazunori*

JAEA-Research 2008-025, 55 Pages, 2008/03

JAEA-Research-2008-025.pdf:8.55MB

Results of joint research on fiscal year 2006 between Japan Atomic Energy Agency (JAEA) and Institute of Research and Innovative (IRI) titled as "Study on investigation of microbial effects for geological disposal" are described in this report. The objective of this study is to develop a method for estimating microbial effects for barrier performance of geological disposal site. The modeling was performed to examine the effect on the change in groundwater chemistry (mainly by electron acceptors) by microbial metabolism as well as microbial activities. In order to use the data (chemical composition, biomass, etc.) in the MINT code, groundwater was collected from the drilled well prepared for chemical and microbial analyses of groundwater. The well was prepared in observation field near Horonobe Underground Research Center of JAEA in fiscal year 2006. Then, numerical modeling using collected data of groundwater with numerical modeling program code "MINT" considering microbial effects was carried out. The modeling was carried out to evaluate the microbial effect for stability of chemical and microbial composition of groundwater. As the result of the modeling, relatively low microbial effect for groundwater composition was observed in particular for the concentration of dissolved methane, methanogen, sulfur reducing bacteria (SRB) and sulfur ion. The result shows that low redox potential is stable in the well in spite of shallow depth.

Journal Articles

Magnetic structure study of antiferromagnet NpPtGa$$_{5}$$ by neutron diffraction

Jonen, Shintaro; Metoki, Naoto; Yamamoto, Etsuji; Homma, Yoshiya*; Aoki, Dai*; Shiokawa, Yoshinobu*; Onuki, Yoshichika

Journal of Alloys and Compounds, 448(1-2), p.84 - 88, 2008/01

 Times Cited Count:1 Percentile:14.05(Chemistry, Physical)

The magnetic structure of NpPtGa$${rm_5}$$ was investigated by neutron diffraction. NpPtGa$${rm_5}$$ exhibits an A-type antiferromagnetic structure with propagation vector $$vec{q}$$ = (0 0 1/2) below $$T_{rm N}$$ = 26 K. The estimated Np magnetic moment is 0.38(5) $$mu_{rm B}$$, and it is oriented parallel to the $$langle$$100$$rangle$$ direction. This small moment would be consistent with the large $$gamma$$ = 123 mJ/(K$${rm^2}cdot$$mol), indicative of the heavy fermion nature. The field-induced anomaly in the magnetic susceptibility is clarified to be a signature for an antiferromagnetic domain change between multi-domains to single-domain states.

Journal Articles

Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years

Kawamura, Kenji*; Parrenin, F.*; Lisiecki, L.*; Uemura, Ryu*; Vimeux, F.*; Severinghaus, J. P.*; Hutterli, M. A.*; Nakazawa, Takakiyo*; Aoki, Shuji*; Jouzel, J.*; et al.

Nature, 448(7156), p.912 - 916, 2007/08

 Times Cited Count:289 Percentile:96.48(Multidisciplinary Sciences)

We present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations.

Journal Articles

Consideration on poroelastic behavior of siliceous rock mass around an opening by stress-seepage coupled analysis

Sanada, Hiroyuki; Matsui, Hiroya; Yamamoto, Takuya*; Aoki, Tomoyuki*; Ogawa, Toyokazu*; Jo, Mayumi*; Fujii, Yoshiaki*

Heisei-19-Nendo Shigen, Sozai Gakkai Hokkaido Shibu Sokai Oyobi Shunki Koenkai Koen Yoshishu, p.9 - 10, 2007/06

Japan Atomic Energy Agency has been conducting the Horonobe Underground Reseach Laboratory Project as a part of geological isolation research and development at Horonobe-town in Hokkaido, Japan. The rocks around URL have high porosity and low permeability. Therefore, the excess pore pressure caused by URL excavation is possible to affect to the stability of surrounding rock. In this point of view, the authors carried out a stress-seepage coupled analysis to understand the process of the pore pressure change due to excavation and the influence to the stability of surrounding rock and support system. As a result, the large excess pore pressure causes a part in surrounding rock on excavation in an anisotropic initial stress condition and it dissipates with time. The pore pressure change causes the complex deformation in the surrounding rock as well. However, the phenomena are not significant influence to the stability of the surrounding rock and support system.

JAEA Reports

Study on investigation of microbial effects for geological disposal, 1 (Joint research)

Tochigi, Yoshikatsu; Yoshikawa, Hideki; Aoki, Kazuhiro; Yui, Mikazu; Honjo, Hideko*; Haginuma, Masashi*; Kawakami, Yasushi*; Suzuki, Kazunori*

JAEA-Research 2007-010, 51 Pages, 2007/03

JAEA-Research-2007-010.pdf:4.82MB

Results of joint research on Fiscal 2005 between Japan Atomic Energy Agency (JAEA) and Institute of Research and Innovative (IRI) titled as "Study for investigation of microbial effects on geological disposal" are described in this report. The objective of this study is constructing advanced method for examining microbial effect for barrier performance of geological disposal site. In fiscal 2005, groundwater and rock core sample have been collected from drilled well on observation field near Horonobe Underground Research Center of JAEA and chemical analysis for collected ground water have been carried out and sensitivity analysis for existing observed data of groundwater with numerical analysis program code "MINT" considering microbial effect have been carried out.

Journal Articles

Stability analysis of underground opening during excavation, taking time-dependent behaviour of surrounding rock mass into consideration

Ogawa, Toyokazu*; Aoki, Tomoyuki*; Jo, Mayumi*; Matsui, Hiroya; Horii, Hideyuki*

Dai-36-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu, p.39 - 44, 2007/01

In case rock exhibits time-dependent deformation, it is important to evaluate this effect on the tunnel stability, since the rock deforms elastically as well as inelatically even at the time of excavation. This paper introduces an engineering approach method to explain the effect of time-dependent deformation of rock at tunnel excavation stages on the stability. The mechanical parameters to describe a Burgers type rheological model are determined, based upon the drained triaxial creep test results performed on mudstone samples. With the parameters determined, plane-strain 2 dimensional numerical analyses are subsequently performed. In the analysis a couple of indices to describe the degree and timing of time-dependent deformation are introduced with reference to the instantaneous elastic deformation, and their effects on the amount of deformation and support pressure subsequent to the support erection are investigated.

Journal Articles

Neutron scattering study of magnetic structure and metamagnetic transition between low- and high-moment states of NpNiGa$$_{5}$$

Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Jonen, Shintaro; Yamamoto, Etsuji; Aoki, Dai*; Homma, Yoshiya*; Haga, Yoshinori; Shiokawa, Yoshinobu*; Onuki, Yoshichika*

Physical Review B, 74(14), p.144413_1 - 144413_12, 2006/10

 Times Cited Count:19 Percentile:64.87(Materials Science, Multidisciplinary)

Systematic neutron scattering experiments have been carried out in order to reveal the magnetic properties of NpNiGa$$_{5}$$. We have observed successive ferromagnetic transitions with the magnetic moment parallel to the tetragonal $$c$$-axis at $$T_{C}$$ = 30 K and 18 K. We have also observed antiferromagnetic reflections with the propergation vector $$q$$ = [1/2 1/2 1/2], coexisting with the ferromagnetic component below $$T_{N}$$ = 18 K. Spin polarized neutron scattering experiments have revealed that only Np carries a magnetic moment. We conclude that the magnetic moments of Np atoms exhibit simple ferromagnetic ordering for ${it T$_{N}$}$ $$<$$ ${it T}$ $$<$$ ${it T$_{C}$}$, while a canted antiferromagnetic structure appears for ${it T}$ $$<$$ ${it T$_{N}$}$. The size of the Np magnetic moment 0.78 $$mu_ {rm B}$$/Np at 3 K have been estimated. The temperature and the magnetic field dependences of these two components have also been quantitatively analyzed. (1) It is quite unusual that the Np total moment increases with the transition from the ferromagnetic to canted antiferromagnetic structure. (2) The metamagnetic transition cannot be explained in terms of a simple spin-flip mechanism with competing interactions and anisotropy. (3) Furthermore, unusual reduction of the Np magnetic moment has been accompanied by the metamagnetic transition. From these three results, we concluded that a remarkable change in the 5$$f$$ electronic state was associated with the transition at $$T_{N}$$ and the metamagnetic transition between the ferromagnetic low-moment state and the canted antiferromagnetic high-moment state. An important role in the 5$$f$$ itinerant system.

Journal Articles

Neutron diffraction study of magnetic structure and successive 5${it f}$ electronic transition in the itinerant antiferromagnet NpRhGa$$_5$$

Jonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Onuki, Yoshichika*

Physical Review B, 74(14), p.144412_1 - 144412_8, 2006/10

 Times Cited Count:26 Percentile:73.22(Materials Science, Multidisciplinary)

Neutron diffraction experiments have been carried out in a single crystal of NpRhGa$$_5$$ in order to reveal the magnetic structure and 5${it f}$ electronic state of this compound. An antiferromagnetic structure with the propagation vector $$vec{q}$$ = (0 0 1/2) appears below $$T_{rm N1}$$. We found a remarkable change in the moment direction at $$T_{rm N2}$$, namely, the Np moment is parallel to the $$c$$-axis for $$T_{rm N2}<T<T_{rm N1}$$ (AF1), but parallel to the $$langle$$110$$rangle$$ direction for $$T<T_{rm N2}$$ (AF2). The magnitude of magnetic moment exhibits a discontinuous change at $$T_{rm N2}$$, indicating that the moment reorientation is associated with a change of the 5${it f}$ electronic state. This transition might be the consequence of the competition between the magnetic and/or quadrupolar interaction in the low-moment and high-moment states. The observed magnetic form factor indicates a dominant contribution from the orbital moment, but the orbital contribution is reduced from the Np free ion state. This is consistent with the itinerant character of the 5${it f}$ electrons in NpRhGa$$_5$$, which is revealed by dHvA experiments and band structure calculations.

Journal Articles

A-Type antiferromagnetic ordering and the transition of the 5$$f$$ electronic state accompanied by unusual moment reorientation in NpRhGa$$_5$$

Jonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.41 - 43, 2006/08

Elastic neutron scattering experiments have been carried out in order to reveal the magnetic structure and 5f electronic state of NpRhGa$$_5$$. This material exhibits two successive antiferromagnetic transition at T$$_{N1}$$ = 36 K and T$$_{N2}$$ = 33 K, respectively. A-type antiferromagnetic structure with the propagation vector q = (0 0 1/2) has been revealed below T$$_{N1}$$. We found a remarkable change in the moment direction, namely the Np moment is parallel and perpendicular to the c-axis for T$$_{N2}$$ $$<$$ T $$<$$ T$$_{N1}$$ and T $$<$$ T$$_{N2}$$, respectively. The magnetic moment exhibits a remarkable jump at T$$_{N2}$$, indicating that the moment reorientation is associated with the change of 5f electronic state. The observed magnetic form factor indicates the dominant contribution of the orbital moment and revealed an itinerant character of the 5f electrons.

45 (Records 1-20 displayed on this page)