Faculty Profiles - SETTAI Rikio

Papers - SETTAI Rikio

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Electrical and Magnetic Properties of R3Al11 (R = La, Ce, Pr, and Nd) Reviewed

Chandrashekhar S. Garde, Tetsuya Takeuchi, Yasunori Nakano, Yuji Takeda, Yuki Ota, Yuichiro Miyauchi, Kiyohiro Sugiyama, Masayuki Hagiwara, Koichi Kindo, Fuminori Honda, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 12 ) 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

High-quality single crystals of R3Al11 (R = La, Ce, Pr, and Nd) with the La3Al11-type orthorhombic crystal structure (space group Immm) have been grown by the Al-flux method. For Ce3Al(11), signatures for ferromagnetic and anti ferromagnetic orderings at T-C = 6.3 K and T-N = 3.2 K, respectively, have been observed in the magnetic susceptibility, magnetization, specific heat, and electrical resistivity. An anti ferromagnet Pr3Al11, on the other hand, exhibits two magnetic transitions at T-N1 = 12.6 K and T-N2 = 3.1 K. An antiferromagnet Nd3Al11 also exhibits multiple magnetic transitions at T-N1 = 13.2 K, T-N2 = 9.4 K, T-N3 = 2.9 K, and T-N4 = 1.77 K in zero magnetic field. The transition at T-N4 has a first-order character. The crystalline electric field (CEF) analysis of magnetic susceptibility, magnetization and specific heat data shows that the CEF splitting is larger for Ce3Al11 than for Pr3Al11 and Nd3Al11. The CEF ground state of Pr3Al11 is a singlet. Magnetic order occurs in this compound owing to the exchange mixing of the CEF around state and low-lying excited states. The ferromagnetic like component of the magnetization for H parallel to [010] is characteristic of R3Al11 (R = Ce, Pr, and Nd), which is most likely due to the Dzialoshinsky-Moriya interaction for two nonequivalent R atoms.

DOI： 10.1143/JPSJ.77.124704

Non-Fermi liquid behavior in the magnetotransport of quasi two-dimensional heavy Fermion compounds CeMIn5 Reviewed

Y. Nakajima, T. Shibauchi, H. Shishido, H. Nakai, K. Behnia, K. Izawa, M. Hedo, Y. Uwatoko, T. Matsumoto, R. Settai, Y. Onuki, H. Kontani, Y. Matsuda

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 69 ( 12 ) 3261 - 3264 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

We observe several non-Fermi liquid behaviors in the normal-state transport properties of CeMIn5 (M: Rh and Co) under pressure at low temperatures: (1) The dc-resistivity shows T-linear dependence, p (x T. (2) The magnitude of Hall coefficient vertical bar R-H vertical bar increases rapidly with decreasing temperature, and reaches a value much larger than vertical bar 1/ne vertical bar at low temperatures. (3) The magnetoresistance displays T- and H-dependence that strongly violate Kohler's rule, and is well scaled by the tangent of the Hall angle, Delta rho(xx)rho(xx) alpha tan(2) Theta(H.) These non-Fermi liquid properties in the electron transport are remarkably pronounced when the AF fluctuations are enhanced in the vicinity of the quantum critical point. Since all of these salient features have been also reported for high-T-c cuprates, we infer that the non-Fermi liquid transport properties capture universal features of strongly correlated electron systems in the presence of strong anti ferromagnetic fluctuations. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2008.06.064

de Haas-van Alphen Effect in LaFePO with Two-Dimensional Cylindrical Fermi Surfaces Reviewed

Hitoshi Sugawara, Rikio Settai, Yusuke Doi, Hiroshi Muranaka, Keisuke Katayama, Hiroshi Yamagami, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 11 ) 2008.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have Succeeded in observing the de Haas-van Alphen (dHvA) effect in LaFePO. the first reported iron-based superconductor in the iron-oxypnictide family. The four detected dHvA frequencies, which correspond to the cross-sectional areas of Fermi surfaces, approximately follow the 1/cos theta dependence,, where theta is the field-tilted angle from the [001] direction to the [100] and [110] directions in the tetragonal structure. This indicates that all the Fermi surfaces are nearly cylindrical, with the two-dimensional electronic state. The cyclotron effective mass, which was determined from the temperature dependence of the dHvA amplitude, is relatively large, ranging from 1.82 to 2.34m(0). The result of energy band structure calculation revealed that the conduction bands mainly consist of 3d electrons of Fe atoms.

DOI： 10.1143/JPSJ.77.113711

Anomalous Electronic Behaviors in Ferromagnetic Kondo Lattice SmFe4P12 Reviewed

Daisuke Kikuchi, Hitoshi Sugawara, Kenya Tanaka, Hidekazu Aoki, Miki Kobayashi, Shotaro Sanada, Keitaro Kuwahara, Yuji Aoki, Hiroaki Shishido, Rikio Settai, Yoshichika Onuki, Hisatomo Harima, Hideyuki Sato

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 11 ) 2008.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

The electronic properties in SmFe4P12 have been investigated by means of the de Haas-van Alphen effect, transverse magnetoresistance, Hall effect, and band structure calculation. We have found a markedly large anisotropy in the cyclotron effective mass of the 47th band Fermi surface despite its nearly spherical shape. Moreover, this mass enhancement in SmFe4P12 is robust against magnetic field. The transverse magnetoresistance increases nearly quadratically with magnetic field for all field directions; this is unexpected for an ordinary uncompensated metal. The Hall coefficient is found to be 4-fold enhanced at low temperature compared with that at room temperature. These anomalies in transport properties are ascribed to the stronger enhancement of the cyclotron effective mass of the 48th band Fermi Surface.

DOI： 10.1143/JPSJ.77.114705

Calorimetric Study in Single Crystalline RCu2Si2 (R: Rare Earth) Reviewed

Yuji Takeda, Nguyen Duc Dung, Yasunori Nakano, Tatsurou Ishikura, Shugo Ikeda, Tatsuma D. Matsuda, Etsuji Yamamoto, Yoshinori Haga, Tetsuya Takeuchi, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 10 ) 2008.10

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

Specific heat measurements on a series of ternary compound RCu2Si2 (R: La, Pr, Nd, Sin, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) single crystals have been performed by the quasi-adiabatic heat Pulse method in the wide temperature range from 0.1 to 80 K. Almost all the compounds show antiferromagnetic orderings at low temperatures. We found the first-order like very sharp specific heat peaks in RCu2Si2 with R = Gd, Tb, Dy, Ho, and Er. Especially, the antiferromagnetic ordering in DyCu2Si2 is found to be a first-order transition. Front the analyses of the temperature dependence of magnetic entropy, we confirmed that the total splitting energy of the crystalline electric field (CEF) scheme of R3+ ion in RCu2Si2 is about 100 K in all the compounds studied here, except for YbCu2Si2. In addition, we observed the nuclear specific heat at low temperatures and estimated the magnitude of internal effective magnetic field H-eff at the nucleus.

DOI： 10.1143/JPSJ.77.104710

Evolution of an Unconventional Superconducting State inside the Antiferromagnetic Phase of CeNiGe3 under Pressure: A Ge-73-Nuclear-Quadrupole-Resonance Study Reviewed

Atsushi Harada, Hidekazu Mukuda, Yoshio Kitaoka, Arumugam Thamizhavel, Yusuke Okuda, Rikio Settai, Yoshichika Onuki, Kouhei M. Itoh, Eugene E. Haller, Hisatomo Harima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 10 ) 2008.10

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We report a Ge-73 nuclear-quadrupole-resonance (NQR) Study on novel evolution of unconventional superconductivity in antiferromagnetic (AFM) CeNiGe3. The measurements of the Ge-73-NQR spectrum and the nuclear spin-lattice relaxation rate (1/T-1) have revealed that the unconventional superconductivity evolves inside a commensurate AFM phase around the pressure (P) where Neel temperature T-N exhibits its maximum at 8.5 K. The superconducting transition temperature T-SC has been found to be enhanced with increasing T-N, before reaching the quantum critical point at which the AFM order collapses. Above T-SC, the AFM structure transits from an incommensurate spin-density-wave order to a commensurate AFM order at T similar to 2 K. accompanied by a longitudinal spin-density fluctuation. With regard to heavy-fermion compounds, these novel phenomena have hitherto never been reported in the P-T phase diagram.

DOI： 10.1143/JPSJ.77.103710

The de Haas-van Alphen oscillation and fermi surface properties of YCu <inf>2</inf>Si<inf>2</inf>

Nguyen Duc Dung, Nguyen Duc Dung, Tatsuma D. Matsuda, Shugo Ikeda, Etsuji Yamamoto, Yoshinori Haga, Yuji Takeda, Toyoaki Endo, Yusuke Doi, Rikio Settai, Hisatomo Harima, Yoshichika Onuki, Yoshichika Onuki

Journal of the Physical Society of Japan 77 ( 9 ) 94702 - 094702-6 2008.9

Language：English Publisher：The Physical Society of Japan (JPS)

We have succeeded in growing a high-quality single crystal of a non-4f reference compound YCu2Si2 for a heavy-fermion superconductor CeCu2Si2, and observed the de Haas-van Alphen (dHvA) oscillation. The detected dHvA branches in YCu2Si 2 indicate that the Fermi surfaces are multiply connected, and the dHvA frequencies are in the range from 9 × 106 to 2 × 108 Oe. These dHvA branches are found to be well explained by the results of energy band calculations. The corresponding cyclotron masses are light, ranging from 0.4 to 1:5m0, and are consistent with the electronic specific heat coefficient of 2.2 mJ/(K2·mol). ©2008 The Physical Society of Japan.

DOI： 10.1143/JPSJ.77.094702

Specific-heat study on the noncentrosymmetric heavy-fermion superconductor CePt3Si Reviewed

Tetsuya Takeuchi, Masahiko Tsujino, Takashi Yasuda, Shin Hashimoto, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE KOREAN PHYSICAL SOCIETY 53 ( 2 ) 1041 - 1045 2008.8

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN PHYSICAL SOC

Specific-heat measurements were performed on a high-quality single crystal of CePt3Si without inversion symmetry in the tetragonal crystal structure. We observed distinct peaks in the specific-heat C at the superconducting transition temperature T-c = 0.46 K and the antiferromagnetic ordering temperature T-N = 2.25 K, compared to the previous data, indicating an improvement of the sample quality. The temperature dependence of the electronic specific-heat coefficient C-e/T below about 0.3 K is well described by the equation of C-e/T = gamma(s) + beta T-s with gamma(s) = 34.1 mJ/K-2.Mol and beta(s) = 1290 mJ/K-3.mol, evidencing the existence of line nodes in the superconducting energy gap. Furthermore, the electronic specific-heat coefficient gamma(s) in the superconducting state indicates a nonlinear magnetic field dependence gamma(s)(H) proportional to root H, which also supports the presence of line nodes.

DOI： 10.3938/jkps.53.1041

Unconventional superconductivity in f-electron systems Reviewed

Y. Onuki, R. Settai, T. Takeuchi, Y. Haga, E. Yamamoto, N. Tateiwa, M. Nakashima, H. Shishido, T. C. Kobayashi, D. Aoki

JOURNAL OF THE KOREAN PHYSICAL SOCIETY 53 ( 2 ) 1034 - 1040 2008.8

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN PHYSICAL SOC

We report pressure-induced superconductivity in antiferromagnetic cerium compounds and a ferromagnetic uranium compound, focusing on the relation between the superconducting state and the Fermi surface instability in CeRhIn5 and the huge upper critical field H-c2 in CeIrSi3 without inversion symmetry in the crystal structure. The pairing interaction is well correlated with ferromagnetism, as well as antiferromagnetism or antiferromagnetic fluctuations. In the recently discovered superconductor NpPd5Al2, superconductivity is found to be located in the vicinity of an antiferromagnetically ordered state. The upper critical field H-c2 is strongly supressed by the large paramagneic effect, and the corresponding magnetization curve indicates a step-like increase at H-c2, producing a first-order phase transition.

Field-induced antiferromagnetism and upper critical field in pressure-induced superconductor CeRhIn5 Reviewed

Yuki Ida, Rikio Settai, Yuuki Ota, Fuminori Honda, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 8 ) 2008.8

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

An antiferromagnet CeRhIn5 is well known to be changed into a superconductor by applying pressure P. Its electronic state is also clarified to be changed at the critical pressure P-c similar or equal to 2.5 GPa under magnetic fields. We measured the low-temperature electrical resistivity of CeRhIn5 in magnetic fields up to 17T and at pressures LIP to 2.45 GPa, and constructed phase diagrams. At P = 2.45 GPa, which is close to P-c similar or equal to 2.5 GPa. there are four kinds of phases, namely, the paramagnetic, superconducting, superconducting and antiferromagnetic, and antiferromagnetic phases in the temperature vs magnetic field phase diagram. The antiferromagnetic phase is found to be induced in the superconducting phase under magnetic fields and expanded in magnetic fields higher than the upper critical field in Superconductivity. Interestingly, the anisotropy of the upper critical field in CeRhIn5 is found to be different from that in a similar non-magnetic heavy-fermion superconductor CeCoIn5, revealing the anisotropic paramagnetic Suppression of the upper critical field.

DOI： 10.1143/JPSJ.77.084708

Fermi surface properties and unconventional superconductivity in rare earth, uranium and transuranium compounds Reviewed

Y. Onuki, R. Settai, H. Shishido, S. Ikeda, T. D. Matsuda, E. Yamamoto, Y. Haga, D. Aoki, H. Harima, H. Harima, H. Yamagami

JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS 10 ( 7 ) 1535 - 1563 2008.7

Language：English Publishing type：Research paper (scientific journal) Publisher：NATL INST OPTOELECTRONICS

We studied the various kinds of electronic states in the f-electron systems of the cubic RX(3) and AnX(3) compounds and the tetragonal RTX(5) and AnTX(5) compounds (R: rare earth, An: Th, U, Np, Pu, T: transition metal, X: Al, Ga, In, Si, Ge, Sn) through the de Haas-van Alphen experiment and the energy band calculation. The former compounds are three dimensional in the electronic states, while the latter compounds are quasi-two dimensional. Pressure experiments were also carried out for antiferromagnets CeIn(3) and CeRhIn(5) to change the electronic state from the antiferromagnetically ordered state to the non-magnetic state, crossing the critical pressure region where the Neel temperature becomes zero. Around this critical pressure region, d-wave superconductivity is induced, and a marked change of the Fermi surface properties from the 4-localized state to the 4f-itinerant state occurs at this critical pressure, revealing the first-order phase transition.

Huge upper critical field and electronic instability in pressure-induced superconductor CeIrSi3 without inversion symmetry in the crystal structure Reviewed

Rikio Settai, Yuichiro Miyauchi, Tetsuya Takeuchi, Florence Levy, Ilya Sheikin, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 7 ) 2008.7

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We measured low-temperature electrical resistivity in a magnetic field as a function of pressure, and studied the superconducting property of CeIrSi3 with a non-centrosymmetric tetragonal structure. CeIrSi3 is an antiferromagnet with a Neel temperature T-N = 5.0 K at ambient pressure, but the antiferromagnetic ordering disappears completely at a pressure P-c = 2.25 GPa. Superconductivity appears in a wide pressure region from 1.8 to about 3.5 GPa, with a maximum transition temperature T-sc similar or equal to 1.6 K at P-c* similar or equal to 2.63 GPa. At around P-c*, the upper critical field H-c2 for the magnetic field H along the [0 01] direction is not destroyed by spin polarization based on Zeeman coupling but possesses an upturn curvature below 1K, revealing a divergent tendency of H-c2 at P-c*, with a huge H-c2(0) similar or equal to 450 kOe. On the other hand, the upper critical field for H parallel to [110] indicates the tendency of Pauli paramagnetic suppression, with H-c2(0) = 95 kOe at 2.65 GPa. This might be a combined phenomenon between the electronic instability at P-c* and the characteristic superconducting property without inversion symmetry in the tetragonal structure.

DOI： 10.1143/JPSJ.77.073705

Magnetotransport properties governed by antiferromagnetic fluctuations in the heavy-fermion superconductor CeIrIn(5) Reviewed

Y. Nakajima, H. Shishido, H. Nakai, T. Shibauchi, M. Hedo, Y. Uwatoko, T. Matsumoto, R. Settai, Y. Onuki, H. Kontani, Y. Matsuda

PHYSICAL REVIEW B 77 ( 21 ) 2008.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

In quasi-two-dimensional Ce(Ir,Rh)In(5) system, it has been suggested that the phase diagram contains two distinct domes with different heavy-fermion superconducting states. Here, we report the systematic pressure dependence of the electron transport properties in the normal state of CeRh(0.2)Ir(0.8)In(5) and CeIrIn(5), which locates in first and second superconducting domes, respectively. We observed non-Fermi liquid behavior at low temperatures in both compounds, including nonquadratic T dependence of the resistivity, large enhancement of the Hall coefficient, and the violation of the Kohler rule in the magnetoresistance. We show that the cotangent of the Hall angle cot Theta(H) varies as T(2), and the magnetoresistance is quite scaled well by the Hall angle as Delta rho(xx)/rho(xx)proportional to tan(2) Theta(H). The observed transport anomalies are common features of CeMIn(5) (M=Co, Rh, and Ir) and high-T(c) cuprates, which suggest that the anomalous transport properties observed in CeIrIn(5) are mainly governed by the antiferromagnetic spin fluctuations not by the Ce-valence fluctuations, which have been proposed to be the possible origin for the second superconducting dome.

DOI： 10.1103/PhysRevB.77.214504

Magnetic and superconducting properties of CeTX3 (T : transition metal and X : Si and Ge) with non-centrosymmetric crystal structure Reviewed

Tomoya Kawai, Hiroshi Muranaka, Marie-Aude Measson, Tetsuya Shimoda, Yusuke Doi, Tatsuma D. Matsuda, Yoshinori Haga, Georg Knebel, Gerard Lapertot, Dai Aoki, Jacques Flouquet, Tetsuya Takeuchi, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 6 ) 2008.6

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We grew single crystals of non-centrosymmetric compounds CeTSi3 and CeTGe3 (T: transition metal), and studied the magnetic properties by measuring the electrical resistivity, magnetic susceptibility and magnetization. We also studied the effect of pressure on the electronic states in antiferromagnets CeTGe3 (T: Co, Rh, Ir) by measuring the resistivity under pressure. No noticeable change of the Neel temperature was observed up to 8 GPa in CeRhGe3 and CeIrGe3, which are far from the magnetic quantum critical point. On the other hand, the Neel temperature in CeCoGe3 was strongly decreased as a function of pressure, and pressure-induced superconductivity was observed in the pressure region from 5.4GPa to about 7.5 GPa. The slope of upper critical field H,2 at 6.5 GPa is found to be extremely large, with an upturn curvature of H,2 with decreasing temperature: -dH,2/dT = 200kOe/K at the superconducting transition temperature T,,, = 0.69 K, revealing unconventional superconductivity.

DOI： 10.1143/JPSJ.77.064716

Split Fermi surface properties of LaTGe3 (T : transition metal) and PrCoGe3 with the non-centrosymmetric crystal structure Reviewed

Tomoya Kawai, Hiroshi Muranaka, Toyoaki Endo, Nguyen Duc Dung, Yusuke Doi, Shugo Ikeda, Tatsuma D. Matsuda, Yoshinori Haga, Hisatomo Harima, Rikio Setta, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 6 ) 2008.6

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We succeeded in growing single crystals of LaTGe3 (T: Fe, Co, Rh, Ir) and PrCoGe3 with the non-centrosymmetric tetragonal crystal structure, and studied the split Fermi surface properties and the magnitude of the antisymmetric spin-orbit interaction 2 vertical bar alpha p perpendicular to vertical bar. The 2 vertical bar alpha p perpendicular to vertical bar value is found to vary when LaTGe3 is changed from T = Co, Rh to Ir, but remains unchanged in LaIrX3 from X = Si to Ge. It is found that this 2 vertical bar alpha p perpendicular to vertical bar value is large in LaIrSi3 and LaIrGe3: 2 vertical bar alpha p perpendicular to vertical bar = 460 K in LaCoGe3, 510 K in LaRhGe3, 1100 K in LaIrSi3, and 1090 K in LaIrGe3 for the main outer orbits named alpha of bands 69 and 70 electron Fermi surfaces, for example. This is due to the large effective atomic number of Ir and a large distribution of the radial wave function of Ir-5d electrons close to the nuclear center, compared with those of Co and Rh. In the case of a paramagnet PrCoGe3 and LaFeGe3 with the relatively large cyclotron mass, the corresponding 2 vertical bar alpha p perpendicular to vertical bar value is found to become small: 2 vertical bar alpha p perpendicular to vertical bar= 280 and 460 K for main orbits ot in PrCoGe3 and LaCoGe3, respectively, and 130 K for main orbits in LaFeGe3.

DOI： 10.1143/JPSJ.77.064717

Single crystal growth and de Haas-van Alphen effect in Lu2Rh3Ga9 with quasi-two-dimensional electronic state Reviewed

Nguyen Duc Dung, Tatsuma D. Matsuda, Yoshinori Haga, Shugo Ikeda, Etsuji Yamamoto, Toyoaki Endo, Rikio Settai, Hisatomo Harima, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 6 ) 2008.6

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We succeeded in growing a single crystal of a layered compound Lu2Rh3Ga9 with an Y2Co3Ga9-type orthorhombic crystal structure by the Ga-flux method. The lattice, positional, and thermal parameters were determined by single-crystal x-ray diffraction measurement. We also measured the electrical resistivity, specific heat, and de Haas-van Alphen (dHvA) effect. The detected dHvA branches were well explained by the results of full potential linear augmented plane-wave (LAPW) energy band calculations. The electronic state was found to be quasi-two-dimensional, indicating nearly cylindrical Fermi surfaces along the [001] direction.

DOI： 10.1143/JPSJ.77.064708

High-quality single crystal growth and Fermi surface properties in f-electron systems Reviewed

Y. Onuki, R. Settai, H. Shishido, S. Ikeda, T. D. Matsuda, E. Yamamoto, Y. Haga, D. Aoki, H. Harima, H. Yamagami

JOURNAL OF CRYSTAL GROWTH 310 ( 7-9 ) 1859 - 1866 2008.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

High-quality single crystals of rare earth and actinide compounds were grown by using several kinds of techniques such as the Czochralski method, flux method, chemical transport method and Bridgman method, together with purification of a uranium ingot by the solid state electrotransport method. For these single crystals, the de Haas-van Alphen experiment was carried out to clarify the Fermi surface properties, focusing on the quasi-two-dimensional electronic state of RTX(5) (R: rare earth, T: transition metal, X: In and Ga) and AnTX(5) (An: Th, U, Np and Pu), which were compared with the results of the energy band calculation. (C) 2007 Published by Elsevier B.V.

DOI： 10.1016/j.jcrysgro.2007.09.032

Pressure-induced superconductivity in antiferromagnet CePd5Al2 Reviewed

Fuminori Honda, Marie-Aude Measson, Yasunori Nakano, Naohisa Yoshitani, Etsuji Yamamoto, Yoshinori Haga, Tetsuya Takeuchi, Hiroshi Yamagami, Katsuya Shimizu, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 4 ) 2008.4

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

A layered compound CePd5Al2, which is an analog of a heavy fermion superconductor NpPd5Al2, is found to be an antiferromagnet with an easy-axis along the tetragonal [001] direction but becomes superconductive in the pressure region from 9 to 12GPa, with the superconducting transition temperature, T-sc = 0.57 K and the upper critical field at 0 K, H-c2(0) = 2.5 kOe, at 10.8 GPa. The quasi-two dimensional Fermi surfaces are also theoretically calculated for CePd5Al2 on the basis of the 4f-itinerant band model.

DOI： 10.1143/JPSJ.77.043701

Unconventional superconductivity and antiferromagnetic quantum phase transition in CeRhIn5 : In-115-NQR study under pressure Reviewed

M. Yashima, S. Kawasaki, H. Mukuda, Y. Kitaoka, H. Shishido, R. Settai, Y. Onuki

PHYSICA B-CONDENSED MATTER 403 ( 5-9 ) 914 - 916 2008.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We report on the pressure (P)-induced phase diagram of antiferromagnetism (AFM) and superconductivity (SC) which emerges at their border at zero magnetic field. The nuclear-quadrupole-resonance (NQR) measurements have revealed that AFM can take place in the superconducting state with T-c similar to 2.1 K at P = 2.05 GPa and the AFM quantum phase transition (QPT) occurs near P = 2.1 GPa. These results reveal the existence of the tetracritical point in the P-T phase diagram of AFM and SC in CeRnIn5. We also found the gapless nature in the uniformly coexisting phase of AFM and SC, indicating an intimate relationship between AFM and SC. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2007.10.062

Enhancement of superconducting transition temperature due to the strong antiferromagnetic spin fluctuations in the noncentrosymmetric heavy-fermion superconductor CeIrSi3: A Si-29 NMR study under pressure Reviewed

H. Mukuda, T. Fujii, T. Ohara, A. Harada, M. Yashima, Y. Kitaoka, Y. Okuda, R. Settai, Y. Onuki

PHYSICAL REVIEW LETTERS 100 ( 10 ) 2008.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We report a Si-29 NMR study on the pressure-induced superconductivity (SC) in an antiferromagnetic (AFM) heavy-fermion compound CeIrSi3 without inversion symmetry. In the SC state at P=2.7-2.8 GPa, the temperature (T) dependence of the nuclear-spin lattice relaxation rate 1/T-1 below T-c exhibits a T-3 behavior without any coherence peak just below T-c, revealing the presence of line nodes in the SC gap. In the normal state, 1/T-1 follows a root T-like behavior, suggesting that the SC emerges under the non-Fermi-liquid state dominated by AFM spin fluctuations enhanced around a quantum critical point. The reason why the maximum T-c in CeIrSi3 is relatively high among the Ce-based heavy-fermion superconductors may be the existence of the strong AFM spin fluctuations. We discuss the comparison with the other Ce-based heavy-fermion superconductors.

DOI： 10.1103/PhysRevLett.100.107003

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