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Journal Articles

Microscopic magnetic property of perpendicular magnetic films of Dy$$_{x}$$Co$$_{100-x}$$ measured using soft X-ray magnetic circular dichroism

Agui, Akane; Mizumaki, Masaichiro*; Asahi, Toru*; Matsumoto, Koji*; Morikawa, Tsuyoshi*; Sayama, Junichi*; Osaka, Tetsuya*

Journal of Physics and Chemistry of Solids, 68(11), p.2148 - 2152, 2007/11

 Times Cited Count:9 Percentile:42.78(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Instrumental design and expected performance of coupled-moderator near-backscattering spectrometer at J-PARC

Takahashi, Nobuaki; Shibata, Kaoru; Sato, Taku*; Tamura, Itaru; Kajimoto, Ryoichi; Harjo, S.; Oikawa, Kenichi; Arai, Masatoshi; Mezei, F.*

Journal of Physics and Chemistry of Solids, 68(11), p.2199 - 2203, 2007/11

 Times Cited Count:7 Percentile:36.42(Chemistry, Multidisciplinary)

A near-backscattering crystal-analyzer neutron inelastic spectrometer, DIANA has been proposed to construct at Materials and Life Science Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). It has firstly been designed to see a decoupled non-poisoned moderator in order to obtain higher intensity and better energy resolution. In deed, the decoupled moderator has a narrower pulse width than a coupled moderator, and so it will give us a better energy resolution. However, the peak neutron flux of the decoupled moderator has only a half of the coupled moderator. In order to decide the best choice of this type of near-backscattering instruments, we have reconsidered instrumental parameters including the type of moderators. We have performed Monte-Carlo neutron ray-tracing simulations, using McStas and have compared these results in various viewpoints such as intensities, resolutions, shape of resolution functions, scan ranges and so on.

Journal Articles

Ferroelectric polarization and magnetic structure in Eu$$_{0.595}$$Y$$_{0.405}$$MnO$$_{3}$$

Kajimoto, Ryoichi; Yokoo, Tetsuya*; Kofu, Maiko*; Noda, Kohei*; Kuwahara, Hideki*

Journal of Physics and Chemistry of Solids, 68(11), p.2087 - 2090, 2007/11

 Times Cited Count:4 Percentile:23.57(Chemistry, Multidisciplinary)

Eu$$_{0.595}$$Y$$_{0.405}$$MnO$$_3$$ shows an antiferromagnetic transition below $$T_N = 47$$K. A spontaneous ferroelectric polarization $$P$$ along $$c$$ appears below $$T_C^c = 25$$K. The direction of $$P$$ then switches to $$a$$ below $$T_C^a = 23$$K. To investigate the relation between $$P$$ and the magnetic structure (MS), we have performed a neutron diffraction study using EXCED diffractometer installed at KENS spallation neutron facility of KEK. Magnetic Bragg peaks with a wave vector (0,0.31,1) were observed. By comparing a magnetic Bragg peak whose scattering vector $$bf{Q}$$ is almost parallel to $$b$$ and that with $$bf{Q}$$ almost parallel to $$c$$, we have succeeded in observing the change of the MS at the temperature ($$T$$) where $$P$$ appears and at $$T$$ where $$P$$ changes its polarization direction. Our observations can be interpreted as formation of a spiral spin structure and change of its easy plane in response to the change of the dielectric properties.

Journal Articles

$$mu$$SR study of the effects of Ce dilution on the development of the heavy-fermion state in (Ce,La)$$_2$$IrIn$$_8$$

Oishi, Kazuki; Heffner, R. H.; Ito, Takashi; Higemoto, Wataru; Morris, G. D.*; Hur, N.*; Bauer, E. D.*; Sarrao, J. L.*; Thompson, J. D.*; MacLaughlin, D. E.*; et al.

Journal of Physics and Chemistry of Solids, 68(11), p.2068 - 2071, 2007/11

 Times Cited Count:2 Percentile:13.01(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Ga NQR relaxation rates in superconductor PuRhGa$$_5$$

Sakai, Hironori; Kambe, Shinsaku; Tokunaga, Yo; Fujimoto, Tatsuya; Walstedt, R. E.*; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.

Journal of Physics and Chemistry of Solids, 68(11), p.2103 - 2106, 2007/11

 Times Cited Count:1 Percentile:7.29(Chemistry, Multidisciplinary)

A lot of attention is currently focused on Pu-based superconductors. These systems have relatively high superconducting (SC) transition temperatures, ${it i.e.,}$ $$T_{rm c}simeq$$ 18 K for PuCoGa$$_{5}$$ and $$T_{rm c}simeq$$ 9 K for PuRhGa$$_{5}$$. Both compounds crystallize in the tetragonal HoCoGa$$_{5}$$ (115) structure, which is well known for the heavy-fermion SC systems Ce$$T$$In$$_{5}$$ ($$T$$=Co, Rh, Ir)with $$T_{rm c} sim$$ 2 K at most. Recently, NMR and NQR experiments have been reported for PuCoGa$$_{5}$$ by Curro et al. and for PuRhGa$$_{5}$$ by our group. In both cases, measurements of $$1/T_{1}$$ using NQR have revealed that the Pu115 superconductors show unconventional superconductivity with an anisotropic gap. Now we have measured the more detailed data of $$1/T_{1}$$ for NQR lines in PuRhGa$$_5$$, especially focusing on the low-lying magnetic excitation in the normal state. From the viewpoint of spin-fluctuations, we will discuss the difference between PuRhGa$$_{5}$$ and PuCoGa$$_{5}$$ and between superconducting Pu115 and non-superconducting An115 series.

Journal Articles

$$^{17}$$O NMR spin-lattice relaxation in NpO$$_2$$; Field-dependent cross-relaxation process driven by $$^{237}$$Np spins

Tokunaga, Yo; Walstedt, R. E.*; Homma, Yoshiya*; Aoki, Dai*; Kambe, Shinsaku; Sakai, Hironori; Fujimoto, Tatsuya; Ikeda, Shugo; Yamamoto, Etsuji; Nakamura, Akio; et al.

Journal of Physics and Chemistry of Solids, 68(11), p.2016 - 2019, 2007/11

 Times Cited Count:2 Percentile:13.01(Chemistry, Multidisciplinary)

In this paper, we report a comprehensive study of $$^{17}$$O nuclear spin-lattice relaxation in NpO$$_2$$ for a wide range of fields and temperatures. In both the paramagnetic and ordered-state regions, a strong, field-dependent $$^{237}$$Np -$$^{17}$$O nuclei cross-relaxation process is observed in addition to the expected background rate. The cross relaxation process, driven by the $$^{237}$$Np spins, is conveyed to the $$^{17}$$O via a greatly enhanced indirect nuclear spin-spin coupling which is described and reported here for the first time. The magnitude and temperature dependence of the indirect coupling are in reasonable accord with a simple theoretical model. The magnitude and temperature dependence of the $$^{237}$$Np $$T_1$$ process are also deduced from the data obtained.

Journal Articles

Local neutron transmutation doping using isotopically enriched silicon film

Yamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi

Journal of Physics and Chemistry of Solids, 68(11), p.2204 - 2208, 2007/11

 Times Cited Count:6 Percentile:32.45(Chemistry, Multidisciplinary)

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from $$^{30}$$Si-enriched materials can serve as a controlled local doping method with tunable dopant concentration, which cannot be realized by conventional doping methods such as ion implantation. In the present study, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. The film contains 7.1 % of $$^{30}$$Si, which is twice higher than that of natural Si. Possible contaminant, fluorine, is lower than 0.6 at.% determined from X-ray photoelectron spectra. Nanostructure of films and changes of electronic properties by the neutron irradiation will also be discussed.

Journal Articles

Magnetic properties of SmRu$$_{4}$$P$$_{12}$$ probed by $$mu$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*

Journal of Physics and Chemistry of Solids, 68(11), p.2072 - 2075, 2007/11

 Times Cited Count:1 Percentile:7.29(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

A Cu NQR study in a $$d$$-electron heavy-fermion system, CaCu$$_{3}$$Ru$$_{4}$$O$$_{12}$$

Kato, Harukazu*; Tsuruta, Takuya*; Nishioka, Takashi*; Matsumura, Masahiro*; Sakai, Hironori; Kambe, Shinsaku

Journal of Physics and Chemistry of Solids, 68(11), p.2187 - 2190, 2007/11

 Times Cited Count:7 Percentile:36.42(Chemistry, Multidisciplinary)

Cu nuclear quadrupole resonance (NQR) studies have been carried out for CaCu$$_{3}$$Ru$$_{4}$$O$$_{12}$$,which has been suggested to show a heavy-fermion-like behavioral though it possess no f electron. A Lorentzian shape of the Cu NQR line with a narrow width implies that no magnetic ordering appears, at least, down to 5 K. The spin-lattice relaxation rate of the Cu nuclei probes a change of the Cu 3$$d$$ electron nature, resulting in the Fermi liquid state at a low temperature. These facts strongly support that the heavy fermion picture is available in the concerned compound.

Oral presentation

The Origin of the excited states in Eu$$^{3+}$$ ions

Mizumaki, Masaichiro*; Agui, Akane; Yoshii, Kenji; Uozumi, Takayuki*

no journal, , 

no abstracts in English

Oral presentation

Quadrupole orders in UPd$$_3$$ probed by $$^{105}$$Pd nuclear quadrupole resonance

Fujimoto, Tatsuya; Haga, Yoshinori; Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Ikeda, Shugo; Matsuda, Tatsuma; Onuki, Yoshichika*

no journal, , 

UPd$$_3$$ shows the antiferro-quadrupole (AFQ) and magnetic phase transitions at $$T_{Q0}=7.5$$K, $$T_{Q1}=6.8$$K and $$T_{Q2}=4.5$$K. We discussed the recent results of nuclear quadrupole resonance (NQR) probed by $$^{105}$$Pd nuclei, especially focusing on the AFQ state below $$T_{Q1}$$. From the NQR spectra obtained, the two point following has been suggested. (1) The discontinuous development of order parameter has been clarified; thus, the first order phase transition has been identified at the $$T_{Q1}$$. (2) The hexagonal Pd sites split into two, in addition, the site ratio between these is 1:2. Up to the present, the neutron diffraction and the X-ray resonant scattering have proposed the different kind of AFQ structure, and unfortunately both of these suggestions could explain the NQR results. In the future, the NQR measurement at the cubic Pd sites and the nuclear magnetic resonance using aligned powder sample is planed to investigate the symmetry of the AFQ state.

Oral presentation

Neutron and X-ray diffraction studies of a frustrated spinel antiferromagnet HgCr$$_2$$O$$_4$$ in high magnetic field

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

no journal, , 

no abstracts in English

Oral presentation

Direct observation of the pressure-induced ferromagnetic order in YbInCu$$_{4}$$

Osakabe, Toyotaka; Kojima, Kenichi*; Hiraoka, Koichi*

no journal, , 

no abstracts in English

Oral presentation

Advances in polarized neutron scattering experiments on TAS-1 at JRR-3

Takeda, Masayasu; Nakamura, Mitsutaka; Shimojo, Yutaka; Kakurai, Kazuhisa; Leli$`e$vre-Berna, E.*; Tasset, F.*; Regnault, L. P.*

no journal, , 

The status of the polarized neutron options on TAS-1 is reported. TAS-1 is a thermal neutron triple-axis spectrometer installed at JRR-3 of JAEA and has been operational since 1991. Following the recent advances in the polarization analysis technique an upgrading program of polarized neutron options for TAS-1 was started five years ago. In this program new doubly-focusing-polarizing Heusler monochromator and analyzer were introduced to TAS-1. In addition, one of three third-generation CRYOPAD(CRYOgenic Polarization Analysis Device)s which were assembled for ILL(D3), CEA-Grenoble(IN22) and JAEA was installed on TAS-1 to enable the spherical polarization analysis. Using the increased polarized neutron flux elastic and inelastic polarized neutron scattering experiments with the conventional setup for the one-dimensional polarization analysis and with CRYOPAD for the three-dimensional polarization analysis are now routinely performed on TAS-1.

Oral presentation

Neutron scattering study of magnetic excitations in overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Yamada, Kazuyoshi*; Tranquada, J. M.*; Frost, C. D.*; Birgeneau, R. J.*; Zhang, H.*

no journal, , 

Neutron scattering experiments have been performed on the overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ ($$0.25 leq x leq 0.30$$). Low energy magnetic excitations ($$omega leq 10$$ meV) show incommensurate peaks for the superconducting samples with a maximum at $$sim 6$$ meV in the energy spectrum. As doping increases, the maximum of the dynamic susceptibility decreases linearly with $$T_c$$ and, finally, the low energy excitations become unobservable at $$x=0.30$$ coincidentally with the disappearance of bulk superconductivity. Time-of-flight measurements revealed that magnetic excitations for $$x=0.25$$ are markedly suppressed in the intermediate energy range ($$20 leq omega leq 80$$ meV), which is apparently consistent with a microscopic phase separation into a superconducting region which retains the antiferromagnetic correlations and a Fermi liquid region which has no magnetic correlations.

Oral presentation

Resonant inelastic X-ray scattering study of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$

Ishii, Kenji; Tsutsui, Kenji*; Toyama, Takami*; Inami, Toshiya; Mizuki, Junichiro; Murakami, Yoichi*; Endo, Yasuo*; Maekawa, Sadamichi*; Kudo, Kazutaka*; Koike, Yoji*; et al.

no journal, , 

(La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ is an attractive material in connection with high-$$T_{rm c}$$ superconductivity because Sr$$_{0.4}$$Ca$$_{13.6}$$Cu$$_{24}$$O$$_{41}$$ becomes a superconductor under high pressure without the CuO$$_2$$ planes. We present RIXS at the Cu $$K$$-edge of (La,Sr,Ca)$$_{14}$$Cu$$_{24}$$O$$_{41}$$ focusing on the momentum dependence of interband excitation across the Mott gap and the intraband excitation below the gap as a function of hole concentration. The experimental results are consistent with the theoretical predictions.

Oral presentation

Paring symmetry in heavy fermion superconductor probed by $$mu$$SR

Higemoto, Wataru

no journal, , 

Paring symmetry in a superconducting state isone of a most crucial information to understand the mechanism of the superconductivity. I report the possible paring symmetries in heavy fermion superconductors CePt$$_3$$Si and PrOs$$_4$$Sb$$_{12}$$, based on the results of muon spin rotation/relaxationmeasurements. CePt$$_3$$Si is the first example of the superconductor lacking an inversion center in the crystal structure. The muon Knight shift at 17 kOe remained unchanged on passing the temperature through $$T_c$$ down to 20 mK. This result indicates that the local spin susceptibility does not change upon the superconducting transition. PrOs$$_4$$Sb$$_{12}$$ is the heavy fermion superconductor exhibiting unconventional superconductivity. At low temperature, no reduction of muon Knight shift passing through $$T_c$$ is observed. The detail of the muon Knight shift results, including an anisotropy and a substitution effect, will be reported.

Oral presentation

Atomic pair distribution function analysis of a nanostructured manganese oxide gold adsorbent

Iikubo, Satoshi; Koyanaka, Hideki*; Shamoto, Shinichi; Takeuchi, Ken*; Kohara, Shinji*; Kodama, Katsuaki; Loong, C.-K.*

no journal, , 

The crystal structure of a nano-manganese oxide, which has high performance as gold adsorbent from seawater has been determined by using the atomic pair distribution function analysis of X-ray and neutron diffraction data. The results complementarily show that the nano-manganese oxide consists mainly of R-MnO$$_2$$.

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