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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.

Journal Articles

Neutron scattering study on U$$T$$Ga$$_{5}$$ and Np$$T$$Ga$$_{5}$$

Metoki, Naoto

Journal of the Physical Society of Japan, 75(Suppl.), p.24 - 29, 2006/08

no abstracts in English

Journal Articles

Incommensurate longitudinal SDW state with a long periodicity in UCu$$_{2}$$Si$$_{2}$$

Honda, Fuminori; Metoki, Naoto; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.121 - 123, 2006/08

no abstracts in English

Journal Articles

Coexistence of antiferromagnetism and heavy-fermion superconductivity in CePt$$_{3}$$Si studied by neutron scattering

Kaneko, Koji; Metoki, Naoto; Bernhoeft, N.*; Matsuda, Tatsuma; Haga, Yoshinori; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.177 - 179, 2006/08

no abstracts in English

Journal Articles

Influence of self-irradiation damage on the Pu-based superconductor PuCoGa$$_5$$ probed by muon spin rotation

Oishi, Kazuki; Ito, Takashi; Higemoto, Wataru; Heffner, R. H.

Journal of the Physical Society of Japan, 75(Suppl.), p.53 - 55, 2006/08

PuCoGa$$_5$$ has attracted much interest because it has a high transition temperature $$T_{rm c}$$ ($$simeq$$ 18 K) compared with other 115 systems. According to the previous $$mu$$SR results, temperature dependence of magnetic penetration depth $$lambda$$ in PuCoGa$$_5$$ shows $$T$$-linear behavior, suggesting that the superconducting order parameter of this material may be $$d$$-wave symmetry. In order to elucidate that point, we have measured the magnetic field dependence of $$lambda$$ in this sample by means of $$mu$$SR technique. At our poster presentation, we discuss the symmetry of superconducting order parameter in PuCoGa$$_5$$ in detail.

Journal Articles

NMR shift measurements of $$^{69}$$Ga in unconventional superconductor PuRhGa$$_{5}$$

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

Journal of the Physical Society of Japan, 75(Suppl.), p.50 - 52, 2006/08

Very recently, we have succeeded in NMR/NQR measurements for PuRhGa$$_{5}$$. PuRhGa$$_{5}$$ is a superconductor with $$T_{c}$$$$approx$$9 K, which is isomorphic to PuCoGa$$_{5}$$ with the higher $$T_{c}$$=18 K. We have reported that PuRhGa$$_{5}$$ is an unconventional superconductor with an anisotropic gap, through the measurement of NQR spin-lattice relaxation rate $$1/T_{1}$$ , while PuCoGa$$_{5}$$ is also reported to be such an anisotropic superconductor. The Knight shift $$K$$ and $$1/T_{1}$$ of NMR under applied field for the normal state of PuRhGa$$_{5}$$ suggest an anisotropic feature of hyperfine and/or spin fluctuation in this system. We will outline the superconducting state and report the nature of the normal state based on the basis of $$K$$ and $$1/T_{1} T$$ results. The difference between PuRhGa$$_{5}$$ and PuCoGa$$_{5}$$ will be also discussed.

Journal Articles

Magnetism and superconductivity in CePt$$_3$$Si probed by muon spin relaxation

Higemoto, Wataru; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Koda, Akihiro*; Saha, S. R.*; Oishi, Kazuki; Kadono, Ryosuke*

Journal of the Physical Society of Japan, 75(Suppl.), p.180 - 182, 2006/08

We report on the Magnetism, magnetic penetration depth and the Knight shift in polycrystalline sample of CePt$$_3$$Si by means of muon spin rotation and relaxation method. The appearance of the internal field under the zero magnetic field in whole volume of the specimen, was observed, which indicating clear evidence of antiferromagnetism. The muon Knight shift was measured down to 20mK at 17kOe. Three different frequencies are seen in the muon spin rotation spectra, which depend on the temperature. The symmetry of the superconducting Cooper pair will be discussed.

Journal Articles

$$mu$$SR studies of Pu metal and the Pu-based superconductor PuCoGa$$_5$$

Heffner, R. H.; Bauer, E. D.*; Chung, B.*; Fluss, M. J.*; Higemoto, Wataru; Ito, Takashi; MacLaughlin, D. E.*; Morales, L. A.*; Morris, G. D.*; Oishi, Kazuki; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.14 - 19, 2006/08

no abstracts in English

Journal Articles

Multipolar phase transition in NpO$$_{2}$$; Comparison with UO$$_2$$ from $$^{17}$$O-NMR

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Ikushima, Kenji; Sakai, Hironori; Ikeda, Shugo; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.33 - 35, 2006/08

The low-temperature phase transition in NpO$$_2$$ has attracted much attention as a promising candidate for a new class of phase transitions associated with octupolar degrees of freedom. In order to elucidate the nature of this exotic phase transition in NpO$$_2$$, we have initiated the first $$^{17}$$O-NMR measurements on this system using a powder sample. From the $$^{17}$$O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below $$T_0$$= 26 K. It has also been shown that the temperature and field dependence of the $$^{17}$$O NMR spectrum can be understood by considering an unconventional hyperfine interaction between the $$^{17}$$O nuclear spins and field-induced antiferromagnetic moments arising from the longitudinal triple-$$vec{q}$$ antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple-$$vec{q}$$ multipole structure in NpO$$_2$$. We will also discuss our recent $$^{17}$$O-NMR results in a single crystal.

Journal Articles

Observation of ferromagnetic and antiferromagnetic correlations in UIr$$_{3}$$B$$_{2}$$

Fujimoto, Tatsuya; Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.113 - 115, 2006/08

The low-dimensional systems exhibit wide-variety of physical properties. In the antiferromagnetic triangular lattice, for instance, resonating valence bond state is expected, furthermore, in one-dimensional (1D) systems, metal-insulator transition (Peierls transition) occurs due to charge-lattice couplings. Up to now, the study of low-dimensional systems has been mostly performed in oxides and organic compounds, but it is rare in the rare-earth and actinide intermetallics. To looking for the novel low-dimensionality in $$f$$-electron systems, we focused on the UIr$$_3$$B$$_2$$, and NMR measurement was carried out. From Knight shift and nuclear spin-lattice relaxation rates, ferromagnetic correlations develop above 50 K, but below 50 K, the emergence of antiferromagnetic correlations was clarified along with the saturation of ferromagnetic correlations. The possible model to explain the obtained result is nesting effect on the 1D Fermi surface, and it is expected that UIr$$_3$$B$$_2$$ will be the typical compound to investigate the physical properties of 1D $$f$$-electrons systems.

Journal Articles

NMR study of antiferromagnet UPtGa$$_{5}$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kato, Harukazu; Walstedt, R. E.; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.127 - 129, 2006/08

Recently, new superconductors have been discovered in Pu-based HoCoGa$$_5$$(115) structure compounds: PuCoGa$$_5$$ ($$T_{c}=18K$$) and PuRhGa$$_5$$ ($$T_{c}=9K$$). The discovery has stimulated a lot of interest in actinide compounds. We report NMR measurements on a high-quality single crystal sample of the non-superconducting U- and Np-based 115 compounds. In order to elucidate universal magnetic properties and the origin of superconductivity in the 115 families, spin-lattice relaxation and Knight shift measurements have been performed systematically in the non-superconducting 115 compounds. Comparison of dynamical properties with the superconducting Pu115 compounds will be presented.

Journal Articles

Single crystal growth and crystal structure of ThRhIn$$_5$$ and LuCoGa$$_5$$

Matsuda, Tatsuma; Haga, Yoshinori; Sakai, Hironori; Ikeda, Shugo; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.85 - 87, 2006/08

Recently quasi-two-dimensional electron state in rare earth and actinide compounds with HoCoGa$$_5$$-type tetragonal crystal structure was attracted a lot attention in relation to heavy fermion superconductivity observed in CeCoIn$$_5$$, CeIrIn$$_5$$ and PuCoGa$$_5$$. In order to elucidate the role of $$f$$ electron in these compounds, it is necessary to compare their electronic state with that of lanthanum and thorium compounds which do not possess the $$f$$-electrons. The number of valence electrons in the thorium compound is the same as that of the corresponding 4$$f^1$$-itinerant cerium compound. We have recently tried to make thorium 115 compounds by indium flux method and have succeeded in discovering the new material of ThRhIn$$_5$$. Crystal structure and quality were confirmed by X-ray diffraction, fluorescent X-ray analysis and EPMA. The lattice parameters were determined to be 4.681(6) $AA and 7.54(1) AA for $a$$ and $$c$$, respectively. The positional parameter $$z$$ of In(4$$i$$) site was also determined to be $$z=0.3069(1)$$.

Journal Articles

Thermodynamics Investigation on pressure-induced superconductor CeNiGe$$_3$$ by ac calorimetry

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Nakashima, Miho*; Thamizhavel, A.*; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.174 - 176, 2006/08

We have investigated the physical properties of Heavy Fermion superconductors by the ac calorimetry under high pressure using a thermocouple. The method is powerful tool since the high sensitive measurement of the heat capacity is possible and the precise pressure dependence of transition temperatures such as the superconducting transition can be determined. In this conference, I would like to report our investigations on the heavy fermion superconductors CePt$$_3$$Si, CeNiGe$$_3$$ and UIr. We have made pressure phase diagram of these compounds and discuss the relation between the magnetism and superconductivity.

Journal Articles

Single crystal growth and magnetic properties of UTe$$_2$$

Ikeda, Shugo; Sakai, Hironori; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; Haga, Yoshinori; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.116 - 118, 2006/08

no abstracts in English

Journal Articles

Resonant magnetic X-ray scattering study of UPd$$_2$$Al$$_3$$

Ishii, Kenji; Kuzushita, Kaori; Murakami, Yoichi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.102 - 104, 2006/08

UPd$$_2$$Al$$_3$$ is an attractive material because of the coexistence of the antiferromagnetic order below $$T_N$$ = 14.5 K and superconductivity below $$T_c$$ = 2 K. In order to discuss the coupling between magnetism and superconductivity by resonant magnetic X-ray scattering (RMXS), nature of the resonance at each absorption edge should be clarified before the measurements across $$T_c$$. Therefore we performed RMXS study from U $$M_1$$ to $$M_4$$ edge at $$T_c < T < T_N$$. In addition to a huge resonance at $$M_4$$-edge, we observed a resonant feature at $$M_2$$-edge which corresponds to the transition from $$3p_{1/2}$$ to $$6d$$ orbitals, while resonance at $$M_1$$-edge and $$M_3$$-edge is rather small.

Journal Articles

Soft X-ray magnetic circular dichroism study of ferromagnetic uranium compounds

Okane, Tetsuo; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Okamoto, Jun*; Mamiya, Kazutoshi*; Muramatsu, Yasuji*; Fujimori, Atsushi; Ochiai, Akira*; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.105 - 106, 2006/08

no abstracts in English

Journal Articles

Band structure and fermi surface of uranium compounds; Soft X-ray angle-resolved photoemission study

Fujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Kobayashi, Keisuke; Fujimori, Atsushi; Yamagami, Hiroshi*; Ikeda, Shugo; Matsuda, Tatsuma; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.99 - 101, 2006/08

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

In the present study, we have performed SX-ARPES experiments on some heavy Fermion (HF) uranium compounds such as UPd$$_2$$Al$$_3$$ using soft X-ray synchrotron radiation from BL23SU of SPring-8. UPd$$_2$$Al$$_3$$ is an HF uranium compound which has transitions into an antiferromagnetic phase at $$T_{rm N} =14$$ K and into a superconducting phase at $$T_{rm C}$$=2 K. To describe the various properties of this compound, the dual model for U 5$$f$$ states is proposed. In this model, two of the three U 5f states are in a localized state while the third electron has delocalized character. We have obtained U 5f sensitive band structure of UPd$$_2$$Al$$_3$$ by SX-ARPES, and the results are compared with this scenario. Temperature dependence of the U 5$$f$$ electronic structure in this compound is also discussed.

Journal Articles

Multipole correlations in low-dimensional $$f$$-electron systems

Onishi, Hiroaki; Hotta, Takashi

Journal of the Physical Society of Japan, 75(Suppl.), p.266 - 269, 2006/08

In order to clarify multipole correlations in $$f$$-electron systems, we investigate a one-dimensional $$f$$-electron model based on a $$j$$-$$j$$ coupling scheme by exploiting a density-matrix renormalization group method. We discuss the effect of a crystalline electric field and the dependence on the change of $$f$$-electron numbers in detail.

Journal Articles

The dHvA experiment under pressure in UIr

Shishido, Hiroaki*; Yamamoto, Etsuji; Haga, Yoshinori; Ikeda, Shugo; Nakashima, Miho*; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.119 - 120, 2006/08

 Times Cited Count:18 Percentile:68.78(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Single crystal growth, superconductivity and Fermi surface study of plutonium compounds

Haga, Yoshinori; Aoki, Dai*; Yamagami, Hiroshi*; Matsuda, Tatsuma; Nakajima, Kunihisa; Arai, Yasuo; Yamamoto, Etsuji; Nakamura, Akio; Homma, Yoshiya*; Shiokawa, Yoshinobu*; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.4 - 9, 2006/08

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

The discovery of the high-temperature in PuCoGa$$_5$$ and PuRhGa$$_5$$ promoted us to extend our research to other actinide compounds. We recently succeeded in growing single crystals of PuRhGa$$_5$$ and performed magnetic measurements and NMR study both in the normal and superconducting states in collaboration with Tohoku university. The magnetic susceptibility consists of Curie-Weiss and temperature-independent terms where the former corresponds to the paramagnetic effective moment close to the 5$$f^5$$ configuration. On the other hand, the superconducting upper critical field is anisotropic. It is explained by the anisotropic mass model with an effective mass ratio of 4, indicating the presence of quasi-two-dimensional Fermi surfaces. These characteristics are reminiscent of those observed in CeCoIn$$_5$$.

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