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Journal Articles

Hall effect in CeRh$$_2$$Si$$_2$$ through its critical pressure

Boursier, R.*; Haen, P.*; Flouquet, J.*; Haga, Yoshinori; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.76 - 77, 2006/05

https://doi.org/10.1016/j.physb.2006.01.168
 Times Cited Count：4 Percentile：21.85(Physics, Condensed Matter)

Hall effect on high-quality crystals of heavy-fermion antiferromagnet CeRh$$_2$$Si$$_2$$ has been measured between 1.6 and 250 K under hydrostatic pressure up to 13 kbars. Residual Hall effect at zero temperature is large, and depends strongly on pressure: it decreases continously and changes sign around the critical pressure.

Journal Articles

Multipole ordering in $$f$$-electron systems

Kubo, Katsunori; Hotta, Takashi

Physica B; Condensed Matter, 378-380, p.1081 - 1082, 2006/05

https://doi.org/10.1016/j.physb.2006.01.428
 Times Cited Count：5 Percentile：26.27(Physics, Condensed Matter)

In order to investigate multipole ordering in $$f$$-electron systems from a microscopic viewpoint, we study the so-called $$Gamma_8$$ models on three kinds of lattices, simple cubic (sc), bcc, and fcc, based on a $$j$$-$$j$$ coupling scheme with $$f$$-electron hopping integrals through $$(ffsigma)$$ bonding. From the $$Gamma_8$$ model, we derive an effective model for each lattice structure by using the second-order perturbation theory with respect to $$(ffsigma)$$. By further applying mean-field theory to the effective model, we find a $$Gamma_{3g}$$ antiferro-quadrupole transition for the sc lattice, a $$Gamma_{2u}$$ antiferro-octupole transition for the bcc lattice, and a longitudinal triple-$$q$$ $$Gamma_{5u}$$ octupole transition for the fcc lattice.

Journal Articles

Magnetic and orbital fluctuations in filled skutterudites

Hotta, Takashi

Physica B; Condensed Matter, 378-380, p.51 - 53, 2006/05

https://doi.org/10.1016/j.physb.2006.01.003
 Times Cited Count：4 Percentile：21.85(Physics, Condensed Matter)

In order to clarify what types of spin and orbital fluctuations dominate over low-temperature electronic properties of Pr-based filled skutterudites, we evaluate multipole susceptibility based on a multiorbital Anderson model constructed from a $$j$$-$$j$$ coupling scheme. It is found that magnetic and quadrupole fluctuations are dominant at low temperatures. When we further include the effect of rattling as dynamical Jahn-Teller phonons, there remain quadrupole and octupole fluctuations, which may induce exotic superconducting pairing.

Journal Articles

Spin-charge-orbital ordering on triangle-based lattices

Onishi, Hiroaki; Hotta, Takashi

Physica B; Condensed Matter, 378-380, p.589 - 591, 2006/05

https://doi.org/10.1016/j.physb.2006.01.157
 Times Cited Count：1 Percentile：6.14(Physics, Condensed Matter)

We investigate the ground-state property of an $$e_{rm g}$$-orbital Hubbard model at quarter filling on a zigzag chain by exploiting the density matrix renormalization group method. When two orbitals are degenerate, the zigzag chain is decoupled to a doble-chain spin system to suppress the spin frustration due to the spatial anisotropy of the occupied orbital. On the other hand, when the level splitting is increased and the orbital anisotropy disappears, a characteristic change in the spin incommensurability is observed due to the revival of the spin frustration.

Journal Articles

High pressure study on the heavy fermion superconductor CePt$$_3$$Si by AC calorimetry

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.381 - 382, 2006/05

https://doi.org/10.1016/j.physb.2006.01.472
 Times Cited Count：1 Percentile：6.14(Physics, Condensed Matter)

We have determined the pressure-temperature phase diagram of heavy-fermion superconductor CePt$$_3$$Si by the ac heat capacity measurement. The N$'e$el temperature $$T_{rm N}$$ = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure $$P_{rm AF}$$ $$simeq$$ 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The phase diagram of CePt$$_3$$Si is thus very unique and has never been reported before for other heavy fermion superconductors.

Journal Articles

Magnetic structure and successive phase transition in NpRhGa$$_{5}$$

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

Physica B; Condensed Matter, 378-380, p.1018 - 1020, 2006/05

https://doi.org/10.1016/j.physb.2006.01.503
 Times Cited Count：7 Percentile：34.02(Physics, Condensed Matter)

The magnetic structure of NpRhGa$$_5$$ has been investigated by neutron scattering. NpRhGa$$_5$$ exhibits two antiferromagnetic phases with transition temperatures at T$$_{N1}$$ = 36 K and T$$_{N2}$$ = 33 K. Neutron scattering experiments revealed an antiferromagnetic structure with propagation vector q = (0 0 1/2) for both, where the Np magnetic moments are oriented parallel to the c-axis for T$$_{N2}$$ $$<$$ T $$<$$ T$$_{N1}$$ and parallel to the [110] direction on basal plane for T $$<$$ T$$_{N2}$$. At T$$_{N2}$$ the reorientation of magnetic moments is accompanied by a sudden increase of magnetic moments, indicative of the first order transition. The magnetic form factor revealed a dominant contribution of the orbital moments.

Journal Articles

Phonons in UCoGa$$_{5}$$

Metoki, Naoto; Kaneko, Koji; Raymond, S.*; Sanchez, J. P.*; Piekarz, P.*; Parlinski, K.*; Ole$'s$, A. M.*; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; et al.

Physica B; Condensed Matter, 378-380, p.1003 - 1004, 2006/05

https://doi.org/10.1016/j.physb.2006.01.543
 Times Cited Count：12 Percentile：48.41(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Single crystal growth and observation of the de Haas-van Alphen effect in ThIn$$_3$$

Matsuda, Tatsuma; Haga, Yoshinori; Shishido, Hiroaki*; Ikeda, Shugo; Harima, Hisatomo*; Settai, Rikio*; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.1021 - 1022, 2006/05

https://doi.org/10.1016/j.physb.2006.01.470
 Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)

We have succeeded in growing a high-quality single crystal of ThIn$$_3$$ with the cubic structure by the In-flux method and measured the de Haas-van Alphen (dHvA) effect. Several dHvA branches were observed, ranging from 9.0 $$times$$ 10$$^6$$ to 9.37 $$times$$ 10$$^8$$ Oe. The experimental results are compared to the dHvA results of CeIn$$_3$$ under pressure of 2.7 GPa, together with the results of energy band calculations.

Journal Articles

Field-induced antiferroquadrupolar order in the heavy fermion superconductor PrOs$$_4$$Sb$$_{12}$$

Kaneko, Koji; Metoki, Naoto; Matsuda, Tatsuma; Kuwahara, Keitaro*; Kogi, Masafumi*; Shiina, Ryosuke*; Mignot, J.-M.*; Gukasov, A.*; Bernhoeft, N.*

Physica B; Condensed Matter, 378-380, p.189 - 191, 2006/05

https://doi.org/10.1016/j.physb.2006.01.349
 Times Cited Count：1 Percentile：6.14(Physics, Condensed Matter)

Neutron diffraction experiments under magnetic fields were carried out on the heavy fermion superconductor PrOs$$_4$$Sb$$_{12}$$ in order to reveal the origin of the field-induced ordered phase (FIOP) for $$H$$$$Vert$$[1,1,0]. The application of magnetic field induces the weak superlattice peaks with the ordering vector $$q$$=(1,0,0) in FIOP, which is the same as for $$H{parallel}$$[0,0,1]. The observed superlattice reflections for $$H$$$$Vert$$[1,1,0] result from the antiferromagnetic component of $$J_x$$+$$J_y$$; the induced tiny antiferromagnetic moments orient parallel to the applied field. This result cannot be explained by magnetic interactions and strongly evidences the underlying AFQ order with $$O_{xy}$$ as a primary order parameter. These facts clarify the dominant role of $$O_{xy}$$-type antiferroquadrupolar interaction in PrOs$$_4$$Sb$$_{12}$$.

Journal Articles

Soft X-ray synchrotron radiation photoemission study on uranium compounds

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

Physica B; Condensed Matter, 378-380, p.995 - 996, 2006/05

https://doi.org/10.1016/j.physb.2006.01.506
 Times Cited Count：2 Percentile：11.86(Physics, Condensed Matter)

Recently, photoemission experiments in soft X-ray region have attracted much attention due to their high sensitivities for bulk electronic structures of strongly correlated electron system. We have carried out the high-resolution photoemission experiments on some uranium compounds using soft X-ray synchrotron radiation from SPring-8 to understand their electronic structures. Bulk- and U 5$$f$$-sensitive band structure and Fermi surface were obtained for itinerant U 5$$f$$ compounds UFeGa$$_5$$ and USb$$_2$$, and they are compared with the results of the band structure calculations treating U 5$$f$$ states as being itinerant. In addition, we show the results of photoemission study on some heavy fermion compounds such as UPd$$_2$$Al$$_3$$ and UNi$$_2$$Al$$_3$$. The temperature dependences of the U 5$$f$$ electronic structure of UPd$$_2$$Al$$_3$$ will be also reported.

Journal Articles

Anisotropic magnetic properties of Ce$$_2$$Ni$$_3$$Ge$$_5$$ single crystal

Thamizhavel, A.*; Sugitani, Ichiro*; Obiraki, Yoshiko*; Nakashima, Miho*; Okuda, Yusuke*; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; Settai, Rikio*; et al.

Physica B; Condensed Matter, 378-380, p.841 - 842, 2006/05

https://doi.org/10.1016/j.physb.2006.01.483
 Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)

We have succeeded in growing single crystals of Ce$$_2$$Ni$$_3$$Ge$$_5$$, which crystallizes in the orthorhombic crystal structure, by the flux method and studied the anisotropic physical properties by measuring the electrical resistivity, magnetic susceptibility and specific heat. The results of these measurements indicate that Ce$$_2$$Ni$$_3$$Ge$$_5$$ undergoes two antiferromagnetic transitions at $$T_{N1}$$=4.9 K and $$T_{N2}$$=4.3 K. The electrical resistivity and susceptibility measurements reveal strong anisotropic magnetic properties. From the specific heat measurement the electronic specific heat coefficient was found to be 90mJ/K$$^2$$mol.

Journal Articles

Pressure-induced superconductivity of Ce$$_2$$Ni$$_3$$Ge$$_5$$

Nakashima, Miho*; Kohara, Hisanori*; Thamizhavel, A.*; Matsuda, Tatsuma; Haga, Yoshinori; Hedo, Masato*; Uwatoko, Yoshiya*; Settai, Rikio*; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.402 - 403, 2006/05

https://doi.org/10.1016/j.physb.2006.01.063
 Times Cited Count：9 Percentile：37.35(Physics, Condensed Matter)

The N$'e$el temperature of Ce$$_2$$Ni$$_3$$Ge$$_5$$ decreases with increasing pressure $$P$$ and becomes zero at a critical pressure $$Pc sim$$ 4 Gpa. The heavy fermion state was found to be formed around $$Pc$$, in which pressure region superconductivity was found below 0.26 K.

Journal Articles

Crossover of the 5f electrons from itinerant to localized in UPtGa$$_5$$

Onuki, Yoshichika; Ikeda, Shugo; Yamagami, Hiroshi*; Galatanu, A.*; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Settai, Rikio*

Physica B; Condensed Matter, 378-380, p.972 - 973, 2006/05

https://doi.org/10.1016/j.physb.2006.01.372
 Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Change of the Fermi surface in CeIn$$_3$$; From localized to itinerant

Settai, Rikio*; Kubo, Tetsuo*; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika; Harima, Hisatomo*

Physica B; Condensed Matter, 378-380, p.417 - 418, 2006/05

https://doi.org/10.1016/j.physb.2006.01.146
 Times Cited Count：7 Percentile：34.02(Physics, Condensed Matter)

We have studied a change of the Fermi surface in an antiferromagnet CeIn$$_3$$ via the de Haas-van Alphen experiment for the magnetic field along $$H$$$$||$$[100] and [111] under pressure at about 2.7 GPa. We have observed a large main spherical Fermi surface named $$a$$, which indicates that the electronic state of 4f electron in CeIn$$_3$$ changes from localized to itinerant. The cyclotron effective mass $$m^*_c$$ of this main Fermi surface is extremely enhanced: $$m^*_c$$ $$simeq$$60 $$m_0$$ at 2.75 GPa for $$H$$$$||$$[100].

Journal Articles

Unconventional supercondnuctivity in the itinerant ferromagnet UGe$$_2$$; $$^{73}$$Ge-NQR study under pressure

Harada, Atsushi*; Kawasaki, Shinji*; Mukuda, Hidekazu*; Kitaoka, Yoshio*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Ito, Kohei*; Haller, E. E.*; Harima, Hisatomo*

Physica B; Condensed Matter, 378-380, p.963 - 964, 2006/05

https://doi.org/10.1016/j.physb.2006.01.368
 Times Cited Count：1 Percentile：6.14(Physics, Condensed Matter)

The superconducting characteristics on the itinerant ferromagnetic superconductor UGe$$_2$$ have been investigated via the $$^{73}$$Ge-NQR measurements under pressure ($$P$$) near the critical pressure $$P_x$$ where the first-order transition takes place from the low-temperature ($$T$$) and low-$$P$$ ferromagnetic phase (FM2) to high-$$T$$ and high-$$P$$ one (FM1). The measurements of nuclear spin-lattice relaxation rate $$T_1$$ have revealed a power-law like behavior as $$T^n$$ without the coherence peak, whereas at low temperatures, it deviates from the $$T^n$$ dependence to a $$T$$-linear like behavior. These results that depend on the pressure are well understood in terms of non-unitary spin-triplet pairing state where the ferromagnetic up-spin band is gapped, but the down-spin band remains gapless at the Fermi level. We will argue an intimate relationship of the onset of SC with FM1 and FM2.

Journal Articles

Unconventional superconductivity in PuRhGa$$_{5}$$; Ga NMR/NQR study

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

Physica B; Condensed Matter, 378-380, p.1005 - 1006, 2006/05

https://doi.org/10.1016/j.physb.2006.01.385
 Times Cited Count：6 Percentile：30.21(Physics, Condensed Matter)

$$^{69,71}$$ Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa$$_{5}$$ with $$T_{c}$$=9 K. The spin-lattice relaxation rate $$1/T_{1}$$ reveals that PuRhGa$$_{5}$$ is an unconventional superconductor having an anisotropic superconducting gap. Moreover, Korringa behavior ($$1/T_{1} T = const.$$) is observed in the normal state below 30 K. This result suggests that the superconductivity sets in after the formation of a Fermi liquid state in this compound.

Journal Articles

Ba$$_{2}$$U$$_{2}$$O$$_{7}$$; A Canted ferromagnet with double-perovskite related orthorhombic structure

Nakamura, Akio; Yoshii, Kenji

Physica B; Condensed Matter, 378-380, p.548 - 549, 2006/05

https://doi.org/10.1016/j.physb.2006.01.247
 Times Cited Count：1 Percentile：6.14(Physics, Condensed Matter)

Ba$$_{2}$$U$$_{2}$$O$$_{7}$$ with double-perovskite related orthorhombic structure has been prepared. The magnetic susceptibility measurement has revealed that this system undergoes successive magnetic transitions at 60 K and 19 K. Curie-Weiss analysis was consistent with the presence of U$$^{5+}$$ in the distorted octahedral sites. The magnetization vs. magnetic field data at 2 K exhibited a clear hysteresis loop without saturation. These results suggest that this material is a canted ferromagnet.

Journal Articles

Magnetic phase diagram and change in 5f electronic states in NpNiGa$$_{5}$$

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

Physica B; Condensed Matter, 378-380, p.1009 - 1010, 2006/05

https://doi.org/10.1016/j.physb.2006.01.471
 Times Cited Count：6 Percentile：30.21(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Anomalous magnetic correlations in heavy fermion Pauli paramagnet UIr$$_3$$B$$_2$$; $$^{11}$$B NMR study

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

Physica B; Condensed Matter, 378-380, p.997 - 998, 2006/05

https://doi.org/10.1016/j.physb.2006.01.382
 Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)

We report $$^{11}$$B NMR results of a single crystal UIr$$_3$$B$$_2$$. The measurement was performed by Fast Fourier Transformation technique, because spectral line width is extremely narrow ($$simeq$$ 10 kHz) and NMR occurs in quite limited r.f. band due to a good sample quality. From temperature variation of Knight shift and nuclear spin-lattice relaxation rate, the development of ferromagnetic correlations was clarified in the temperature range above $$T^{*} simeq 50$$ K. On the other hand, the magnetic dynamics was changed into another novel state below $$T^{*}$$; ferromagnetic correlations are restrained, meanwhile antiferromagnetic correlations are newly emerged. To explain this characteristic ground state, the one-dimensional $$5f$$ electrons state due to the unique structural lattice of UIr$$_3$$B$$_2$$ was proposed.

Journal Articles

Multipolar ordering in NpO$$_2$$ probed by NMR

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; Walstedt, R. E.; Yasuoka, Hiroshi

Physica B; Condensed Matter, 378-380, p.929 - 930, 2006/05

https://doi.org/10.1016/j.physb.2006.01.353
 Times Cited Count：3 Percentile：17.14(Physics, Condensed Matter)

We have initiated the first $$^{17}$$O-NMR measurements in the ordered state of NpO$$_2$$. From the $$^{17}$$O-NMR spectrum, we have confirmed the occurrence of two inequivalent oxygen sites below $$T_0$$= 26 K. It has also been shown that the $$^{17}$$O-NMR spectrum in the ordered state 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-$$bf{q}$$ antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple-$$bf{q}$$ multipole structure in NpO$$_2$$.

26 (Records 1-20 displayed on this page)