Faculty Profiles - SETTAI Rikio

Papers - SETTAI Rikio

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Unconventional heavy-fermion superconductor CeCoIn5: dc magnetization study at temperatures down to 50 mK

T. Tayama, A. Harita, T. Sakakibara, Y. Haga, H. Shishido, R. Settai, Y. Onuki

Physical Review B - Condensed Matter and Materials Physics 65 ( 18 ) 1805041 - 1805044 2002.5

Language：English Publishing type：Research paper (scientific journal)

dc magnetization measurements on CeCoIn5 reveal a first-order phase transition at Hc2 for both H∥a and c axes in the isothermal magnetization M(H) below 0.7 K, indicating a strong Pauli paramagnetic suppression in the even-parity pairing. M(T) in the normal state above Hc2 exhibits non-Fermi-liquid behavior down to 150 mK, implying the existence of antiferromagnetic fluctuations behind the unconventional superconductivity. We observed an unusual peak effect for H∥c in fields 5-30 kOe below 150 mK(=0.06Tc), whose anomalous temperature dependence cannot be simply explained by ordinary mechanisms.

Unconventional heavy-fermion superconductor CeCoIn5: dc magnetization study at temperatures down to 50 mK Reviewed

T Tayama, A Harita, T Sakakibara, Y Haga, H Shishido, R Settai, Y Onuki

PHYSICAL REVIEW B 65 ( 18 ) 2002.5

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

dc magnetization measurements on CeCoIn5 reveal a first-order phase transition at H-c2 for both Hparallel toa and c axes in the isothermal magnetization M(H) below 0.7 K, indicating a strong Pauli paramagnetic suppression in the even-parity pairing. M(T) in the normal state above H-c2 exhibits non-Fermi-liquid behavior down to 150 mK, implying the existence of antiferromagnetic fluctuations behind the unconventional superconductivity. We observed an unusual peak effect for Hparallel toc in fields 5-30 kOe below 150 mK(=0.06T(c)), whose anomalous temperature dependence cannot be simply explained by ordinary mechanisms.

DOI： 10.1103/PhysRevB.65.180504

Pressure study of an antiferromagnet, CeMg2Cu9 Reviewed

H Nakawaki, Y Inada, R Asai, M Yamada, T Okubo, S Ikeda, A Thamizhavel, TC Kobayashi, R Settai, E Yamamoto, Y Onuki

JOURNAL OF PHYSICS-CONDENSED MATTER 14 ( 14 ) L305 - L311 2002.4

Language：English Publisher：IOP PUBLISHING LTD

We have studied the effect of pressure on the electrical resistivity of the antiferrornagnet CeMg2Cu9 which crystallizes in the hexagonal structure. The structure is built up of alternating MgCu2 Laves-type and CeCu5-type layers along the [0001] direction. The Neel temperature T-N = 2.7 K at ambient pressure decreases with increasing pressure p and disappears at a critical pressure p(e) similar or equal to 2.5 GPa. Correspondingly, the residual resistivity rho(0) and the coefficient A in a Fermi-liquid relation rho = rho(0) + AT(2) are found to have maximum values around p(e).

DOI： 10.1088/0953-8984/14/14/101

Thermal expansion and magnetostriction studies in a heavy-fermion superconductor, CeCoIn5 Reviewed

T Takeuchi, H Shishido, S Ikeda, R Settai, Y Haga, Y Onuki

JOURNAL OF PHYSICS-CONDENSED MATTER 14 ( 12 ) L261 - L266 2002.4

Language：English Publisher：IOP PUBLISHING LTD

We have measured the iso-ficld thermal expansion and magnetostriction in a heavy-fermion superconductor, CeCoIn5, with tetragonal structure. The thermal expansion at zero field shrinks for the [100] direction in the superconducting state, while it expands for [001]. The magnetic field effect on the superconducting transition at the superconducting transition temperature T-c is remarkable for [001]. The longitudinal magnetostriction for H parallel to [001] shows a continuous field dependence with a bend at the upper critical field H-c2 below T-c but this feature changes into a steplike transition below about 0.7 K, indicating that the transition changes from the second to the first order. We have also measured the thermal expansion at high temperatures, which is compared with those in CeIrIn5 and CeRhIn5.

DOI： 10.1088/0953-8984/14/12/105

mu SR studies on heavy fermion superconductors CeIrIn5 and CeCoIn5 Reviewed

W Higemoto, A Koda, R Kadono, Y Kawasaki, Y Haga, D Aoki, R Settai, H Shishido, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 ( 4 ) 1023 - 1026 2002.4

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

We report that the muon spin relaxation rate under zero-external field in the heavy-fermion compound CeTrIn5 (Tr=Ir. Co) is independent of temperature down to 20 mK, demonstrating the absence of magnetism due to long-range magnetic order and/or to the breakdown of time-reversal symmetry in the superconducting state. The magnetic penetration depth deduced by the muon spin relaxation rate under a transverse field is lambda similar to 6700 Angstrom for CeIrIn5 at 402 G and similar to5500 Angstrom for CeCoIn5 at 3 kG.

DOI： 10.1143/JPSJ.71.1023

Scattering rate of quasiparticles both in the normal and superconducting mixed states in CeCoIn5 studied by the dHvA effect Reviewed

R Settai, H Shishido, S Ikeda, M Nakashima, D Aoki, Y Haga, H Harima, Y Onuki

PHYSICA B-CONDENSED MATTER 312 123 - 125 2002.3

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

We observed the de Haas-van Alphen (dHvA) oscillation both in the normal and superconducting mixed states in a heavy fermion superconductor CeCoIn5. The dHvA oscillation due to a main Fermi surface is observed in the mixed state just below the upper critical field H-c2, indicating a large scattering rate of quasi-particles. We determined the Dingle temperatures both in the normal and the mixed states. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01167-X

Quasi-two-dimensional Fermi surfaces in rare earth and uranium compounds Reviewed

Y Onuki, R Settai, D Aoki, H Shishido, Y Haga, Y Tokiwa, H Harima

PHYSICA B-CONDENSED MATTER 312 13 - 15 2002.3

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

We present the quasi-two-dimensional Fermi surface studies in RTIn5 (R: rare earth, T: Co, Rh and Ir), together with UTGa5. The present quasi-two dimensionality is closely related to the unique crystal structure elongated along the [001] direction, which brings about a flat Brillouin zone and produces cylindrical but highly corrugated Fermi surfaces along [001]. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01155-3

Heat capacity of the pressure-induced superconductivity in itinerant ferromagnet UGe2 Reviewed

N Tateiwa, TC Kobayashi, K Amaya, Y Haga, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 312 109 - 111 2002.3

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

Recently, co-existence of the ferromagnetism and superconductivity was reported in the high-pressure region (1.0-1.6 GPa) in UGe2. We performed the heat capacity measurement on UGe2 under high pressure. At 1.15 GPa, we found a peak corresponding to the superconducting transition. The superconducting temperature T-sc and DeltaC/(gammaTSC) are 0.6 K and 0.25, respectively. The superconducting transition was also confirmed by the appearance of the Meissner effect in the AC susceptibility. From these results, we confirm a bulk nature of the superconductivity in UGe2. The value of C/T (similar to 95 mJ/molK(2)) just above Tsc at 1.15 GPa is as much as 3 times larger than that at ambient pressure, which indicates a large mass enhancement of quasiparticles under high pressure. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01076-6

Magnetic and Fermi surface properties of UNiGa5 Reviewed

Y Tokiwa, Y Haga, N Metoki, S Ikeda, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 312 294 - 296 2002.3

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

In order to investigate the magnetic structure and Fermi surface properties of UNiGa5 we have performed elastic neutron scattering and de Haas-van Alphen(dHvA) experiments. In the neutron scattering experiment using a single crystalline sample, we determined the antiferromagnetic propagation vector Q= (1/2, 1/2,1/2) in UNiGa5. In the dHvA experiment, we observed four branches. Two branches indicate cylindrical Fermi surface and the other two branches correspond to ellipsoidal ones. The cyclotron mass was not large, ranging from 1.3 to 3.1m(0). (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01321-7

de Haas-van Alphen effect in the filled skutterudite CeRu4Sb12 Reviewed

H Sugawara, K Abe, TD Matsuda, Y Aoki, H Sato, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 312 264 - 266 2002.3

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

We have succeeded in observing the de Haas-van Alphen effect in the filled skutterudite CeRu4Sb12. The results predict a large difference in the Fermi surface topology compared to the reference compound LaRu4Sb12. The cyclotron effective mass m(c)* enhanced to 4.6 similar to 5.8m(0) indicates a strong electron correlation in this compound. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01298-4

De Haas-van Alphen effect in UIr Reviewed

E Yamamoto, Y Haga, H Shishido, H Nakawaki, Y Inada, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 312 302 - 303 2002.3

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

We have succeeded in growing a high-quality single crystal of UIr with the monoclinic structure by the Czochralski pulling method in a tetra-arc furnace. UIr is a ferromagnetic compound. Its Curie temperature T-C is 46 K and the magnetic moment is found to be oriented along the [101] direction by the magnetization measurement. The magnetic moment is 0.5mu(B)/U. We have observed the de Haas-van Alphen oscillation. All the detected branches have heavy cyclotron effective masses ranging from 9.6 to 32m(0). They are consistent with the electronic specific heat coefficient gamma = 48.5 mJ/K-2 mol. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01331-X

De Haas-van Alphen effect in CeRh2Si2 under pressure Reviewed

S Araki, M Nakashima, H Nakawaki, R Settai, H Harima, Y Onuki

PHYSICA B-CONDENSED MATTER 312 435 - 436 2002.3

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

We observed de Haas-van Alphen (dHvA) oscillations in CeRh2Si2 at 1.3 GPa, higher than the quantum critical pressure p(c)similar or equal to1.0 GPa. Three observed dHvA branches correspond to the result of the 4f-itinerant model. Their cyclotron masses are large, being 24m(0), 29m(0) and 31m(0), about 4 times larger than the corresponding band masses. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01359-X

de Haas-van Alphen effect on PrRu4Sb12 Reviewed

TD Matsuda, K Abe, F Watanuki, H Sugawara, Y Aoki, H Sato, Y Inada, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 312 832 - 833 2002.3

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

The angular dependence of de Haas-van Alphen effect has been measured to reveal the electronic structure of filled skutterudite PrRu4Sb12. The angular dependence of de Haas-van Alphen frequency of PrRu4Sb12 is in good agreement with that of LaRu4Sb12. Compared with PrFe(4)Pi(12), no anomalous enhancement of cyclotron effective mass has been observed in this system. This change of electronic structure is attributed to the difference in the c - f hybridization strength, which is expected from the large difference in the lattice parameters. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01260-1

Angular position of nodes in the superconducting gap of 2D unconventional superconductors Reviewed

K Izawa, H Yamaguchi, Y Matsuda, T Sasaki, T Fukase, Y Yoshida, R Settai, Y Onuki

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 367 ( 1-4 ) 15 - 19 2002.2

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

The superconducting gap structure, especially the direction of the nodes, is an unresolved issue in most of unconventional superconductors. Here, we have measured the thermal conductivity of 2D unconventional superconductors, spin-triplet Sr2RuO4 and heavy fermion CeCoIn5, in magnetic field rotating within the planes. On the basis of the angular variation of the thermal conductivity, we demonstrate that the gap function of Sr2RuO4 is d(k) = Delta(0)(z) over cap (k(x) + ik(y)) (cos ck(2) + alpha), and the gap function of CeCoIn5 is d(x2-y2). (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(01)00979-0

Fermi Surface in CeRh2Si2 under Pressure Reviewed

Shingo Araki, Miho Nakashima, Rikio Settai, Hisatomo Harima, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 273 - 275 2002.1

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

We observed the de Haas-van Alphen (dFlvA) oscillations in CeRh2Si2 under pressures up to 1.54 GPa, Three dFIvA branches at higher pressure than the critical pressure p(c) similar or equal to 1.06 GPa, are well explained by the result of the 4f-itinerant model. Their cyclotron masses are large, being 24m(0), 30m(0) and 31m(0), which are about 4 times larger than the corresponding band masses.

DOI： 10.1143/JPSJS.71S.273

Pressure-temperature phase diagram of antiferromagnetism and superconductivity in CeRhIn5 and CeIn3: In-115-NQR study under pressure Reviewed

S Kawasaki, T Mito, GQ Zheng, C Thessieu, Y Kawasaki, K Ishida, Y Kitaoka, T Muramatsu, TC Kobayashi, D Aoki, S Araki, Y Haga, R Settai, Y Onuki

PHYSICAL REVIEW B 65 ( 2 ) 2002.1

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

We report the pressure (P)-temperature (T) phase diagram of antiferromagnetism and superconductivity in CeRhIn5 and CeIn3 revealed by the In-115 nuclear-spin-lattice-relaxation (T-1) measurement. In the itinerant magnet CeRhIn5, we found that the Neel temperature T-N is reduced at P greater than or equal to 1.23 GPa with an emergent pseudogap behavior. In CeIn3, the localized magnetic character is robust against the application of pressure up to Psimilar to1.9 GPa, beyond which the system evolves into an itinerant regime in which the resistive superconducting phase emerges. We discuss the relationship between the phase diagram and the magnetic fluctuations.

DOI： 10.1103/PhysRevB.65.020504

Fermi surface, magnetic and superconducting properties of LaRhIn5 and CeTIn5 (T : Co, Rh and Ir) Reviewed

H Shishido, R Settai, D Aoki, S Ikeda, H Nakawaki, N Nakamura, T Iizuka, Y Inada, K Sugiyama, T Takeuchi, K Kindo, TC Kobayashi, Y Haga, H Harima, Y Aoki, T Namiki, H Sato, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 ( 1 ) 162 - 173 2002.1

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

We have studied Fermi surface properties of LaRhIn5 and CeTIa(5) (T: Co, Rh and Ir) via the de Haasvan Alphen (dHvA) experiment. The Fermi surface of a non-4f reference compound LaRhIn5 is quasi-two dimensional, reflecting the unique tetragonal crystal structure, which is consistent with the result of FLAWP energy band calculations. The Fermi surface of an antiferromagnet CeRhIn5 is similar to that of LaRhIn5 although the cyclotron mass in CeRhIn5 is roughly by one order larger than that in LaRhIn5. Both Fermi surfaces are. however, different from those of CeCoIn5 and CcIrIn(5) which are well explained by the 4f-itinerant band model. The 4f electrons in CeRhIn5 thus do not contribute to the volume of ate Fermi surface. We have also studied magnetic and superconducting properties of CeCoIn5 and CeIrIn5.

DOI： 10.1143/JPSJ.71.162

Exotic heavy-fermion state in the filled skutterudite (formula presented) uncovered by the de Haas-van Alphen effect Reviewed

H. Sugawara, T. D. Matsuda, K. Abe, Y. Aoki, H. Sato, S. Nojiri, Y. Inada, R. Settai, Y. Ōnuki

Physical Review B - Condensed Matter and Materials Physics 66 ( 13 ) 1 - 5 2002

Language：English Publishing type：Research paper (scientific journal)

We report the de Haas-van Alphen (dHvA) experiment on the filled skutterudite (formula presented) exhibiting apparent Kondo-like behaviors in the transport and thermal properties. We have found enormously enhanced cyclotron effective mass (formula presented) in the high field phase, which indicates that (formula presented) is the first Pr compound in which really heavy mass has been unambiguously confirmed. Also in the low field nonmagnetic ordered phase (LOP), we observed the dHvA branch with (formula presented) that is quite heavy taking into account its small Fermi surface volume (0.15% of the Brillouin zone size). The insensitivity of mass in LOP against the magnetic field suggests that the quadrupolar interaction plays a main role both in the mass renormalization and the LOP formation. © 2002 The American Physical Society.

DOI： 10.1103/PhysRevB.66.134411

Unconventional heavy-fermion superconductor (formula presented) dc magnetization study at temperatures down to 50 mK Reviewed

T. Tayama, A. Harita, T. Sakakibara, Y. Haga, H. Shishido, R. Settai, Y. Onuki

Physical Review B - Condensed Matter and Materials Physics 65 ( 18 ) 1 - 4 2002

Language：English Publishing type：Research paper (scientific journal)

DC magnetization measurements on (formula presented) reveal a first-order phase transition at (formula presented) for both (formula presented) and c axes in the isothermal magnetization (formula presented) below 0.7 K, indicating a strong Pauli paramagnetic suppression in the even-parity pairing. (formula presented) in the normal state above (formula presented) exhibits non-Fermi-liquid behavior down to 150 mK, implying the existence of antiferromagnetic fluctuations behind the unconventional superconductivity. We observed an unusual peak effect for (formula presented) in fields 5-30 kOe below (formula presented) whose anomalous temperature dependence cannot be simply explained by ordinary mechanisms. © 2002 The American Physical Society.

DOI： 10.1103/PhysRevB.65.180504

(formula presented)-NQR evidence for unconventional superconductivity in (formula presented) under pressure Reviewed

S. Kawasaki, T. Mito, Y. Kawasaki, G. Zheng, Y. Kitaoka, H. Shishido, S. Araki, R. Settai, Y. Ōnuki

Physical Review B - Condensed Matter and Materials Physics 66 ( 5 ) 1 - 4 2002

Language：English Publishing type：Research paper (scientific journal)

We report evidence for unconventional superconductivity in (formula presented) at a pressure (formula presented) above the critical pressure (formula presented) revealed by measurements of the nuclear-spin-lattice-relaxation time (formula presented) and ac susceptibility (ac- (formula presented) Both measurements of (formula presented) and ac- (formula presented) have pointed to a superconducting transition at (formula presented) which is much lower than the onset temperature (formula presented) at zero resistance. The temperature dependence of (formula presented) shows no coherence peak just below (formula presented) indicative of an unconventional nature for the superconductivity induced in (formula presented). © 2002 The American Physical Society.

DOI： 10.1103/PhysRevB.66.054521

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