Faculty Profiles - SETTAI Rikio

Papers - SETTAI Rikio

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Fermi surface properties and metamagnetism in the antiferroquadrupolar compound PrPb3 Reviewed

D Aoki, Y Katayama, R Settai, Y Inada, Y Onuki, H Harima, Z Kletowski

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 66 ( 12 ) 3988 - 3995 1997.12

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

We have measured the de Haas-van Alphen effect of PrPb3 whose antiferroquadrupolar ordering occurs at 0.41K. Main Fermi surfaces consist of four closed ones, which are almost spherical. These Fermi surfaces are the same as those of a non-f reference compound LaPb3 in topology, although the cyclotron effective masses are 2 to 6 times larger than those of LaPb3. The cyclotron effective masses are temperature-dependent, which starts gradually with decreasing the temperature below 1K. A metamagnetic transition is also found to occur at about 70 kOe below 0.6 K through the magnetization, magnetostriction and AC susceptibility measurements. These phenomena are closely related to the antiferroquadrupolar ordering at O.4K.

DOI： 10.1143/JPSJ.66.3988

High resolution photoemission study of CeRu2Si2 Reviewed

M Tsunekawa, S Suga, A Kimura, T Matsushita, T Muro, S Ueda, H Daimon, S Imada, T Nakatani, Y Saitoh, T Iwasaki, A Sekiyama, A Fujimori, H Ishii, T Miyahara, T Hanyu, H Namatame, M Taniguchi, E Shigemasa, O Sakai, R Takayama, R Settai, H Azuma, Y Onuki

SOLID STATE COMMUNICATIONS 103 ( 12 ) 659 - 662 1997.9

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

High resolution Ce 4d --> 4f resonance photoemission study was done for CeRu2Si2. The Ce 4f spectrum has shown two prominent peaks around 0.3 and 2.5 eV. The 0.3 eV peak has clearly shown an additional structure closer to the Fermi level, whose intensity decreases at higher temperatures. This intensity reduction is ascribed to the tail of the Kondo resonance peak. (C) 1997 Elsevier Science Ltd.

DOI： 10.1016/S0038-1098(97)00266-4

Fermi surface properties of ferromagnetic CeRu2Ge2 Reviewed

H Ikezawa, H Aoki, M Takashita, CJ Haworth, S Uji, T Terashima, K Maezawa, R Settai, Y Onuki

PHYSICA B 237 210 - 211 1997.7

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

We have performed a dHvA effect study on the ferromagnetic heavy fermion compound CeRu2Ge2. Six spin-split dHvA frequency branches are observed in the (100) and (110) planes. The angular dependence of the dHvA frequencies is mostly consistent with the result reported by King and Lonzarich (KL), except that we have successfully observed the dHvA signal from a large hole surface for fields parallel to [001] and a new low-frequency branch. The effective masses measured for fields in the (001) plane agree with those of KL and do not depend on field strength. On the other hand, those for fields parallel to [001] differ considerably from those of KL and are found to decrease with increasing field. Moreover, the measured effective mass of the large hole surface is less than half of the value expected from the electronic specific heat coefficient.

DOI： 10.1016/S0921-4526(97)00102-6

DeHaas-vanAlphen effect and the metamagnetic transition based on the quadrupole moment in PrCu2 Reviewed

M Abliz, R Settai, P Ahmet, D Aoki, K Sugiyama, Y Onuki

PHILOSOPHICAL MAGAZINE B-PHYSICS OF CONDENSED MATTER STATISTICAL MECHANICS ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES 75 ( 3 ) 443 - 462 1997.3

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

We have studied the metamagnetic transition in the Van Vleck paramagnetic compound PrCu2. This transition brings about an interchange between the easy (a) and the hard (c) axes' directions of the magnetization which is reflected in drastic changes of the magnetoresistance and the de Haas-van Alphen oscillation. The origin of this metamagnetic transition is ascribed to the switching of the direction of the quadrupole moment in the 4f levels.

DOI： 10.1080/13642819708202330

Magnetic properties of heavy fermion superconductors UPt3 and URu2Si2 Reviewed

K Tenya, M Ikeda, T Tayama, K Kuwahara, H Amitsuka, T Sakakibara, E Yamamoto, K Maezawa, N Kimura, R Settai, Y Onuki

PHYSICA B 230 345 - 347 1997.2

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

The effects of the normal state paramagnetism on the superconductivity of UPt3 and URu2Si2 were investigated by means of static magnetization measurements. While the upper critical field of URu2Si2 seems to be paramagnetically suppressed, no clear spin reduction is observed in the magnetization curves. The paramagnetic polarization in UPt3 for H perpendicular to c (H parallel to c) is as large as (slightly suppressed below) the normal-state value, although the normal state spin susceptibility is considered to be largest for H perpendicular to c. The results of UPt3 point to an odd-parity pairing with a discernible anisotropy in the pair-spin state.

DOI： 10.1016/S0921-4526(96)00715-6

Metamagnetic magnetization in DyCu2 Reviewed

K Sugiyama, Y Yoshida, D Aoki, R Settai, T Takeuchi, K Kindo, Y Onuki

PHYSICA B 230 748 - 751 1997.2

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

We have observed two metamagnetic transitions in the field along the c-axis in DyCu2, which occurs at 8 and 14T at 1.3K. A higher field transition corresponds to the previous data obtained by Hashimoto et al. [5] and decreases as the temperature increases up to the Neel temperature T-N, while a lower field transition shows no temperature dependence and disappears above T-N. The former transition field increases linearly as the temperature increases above T-N. This temperature dependence is similar to that in PrCu2 of which the metamagnetic transition is based on the quadrupole moment.

DOI： 10.1016/S0921-4526(96)00829-0

Anisotropic magnetoresistance of CeNiSn Reviewed

Y Inada, T Ishida, H Azuma, D Aoki, R Settai, Y Onuki, K Kobayashi, T Takabatake, G Nakamoto, H Fujii, K Maezawa

PHYSICA B 230 690 - 694 1997.2

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

We have measured the magnetoresistance at high fields up to 15 T and at low temperatures down to 0.4 K for CeNiSn with the orthorhombic structure. The longitudinal magnetoresistance (J parallel to H) is small in magnitude for the magnetic field H parallel to b- and c-axis. On the other hand, the positive magnetoresistance is found to become dominant with the decrease of temperature for H parallel to b- and c-axis in the transverse configuration (J perpendicular to H). For H parallel to a, the magnetoresistance is negative for any current direction. These experimental results have been discussed on the basis of the cyclotron motion of the compensated carriers with closed Fermi surfaces and the reduction of the anisotropic hybridization gap.

DOI： 10.1016/S0921-4526(96)00804-6

The magnetic properties of RNi(4)Sn(2) (R=La,Ce,Pr,Nd and Sm) compounds Reviewed

SK Dhar, Y Kimura, M Kozaki, R Settai, Y Onuki, W Zhao, JK Tang

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 66 ( 1 ) 235 - 241 1997.1

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

We have investigated the magnetic behavior of RNi(4)Sn(2) compounds (R = La, Ce, Pr, Nd and Sm) by magnetisation, electrical resistivity and the heat capacity measurements. The alloys with magnetic rare earth ions order magnetically and the ordering is antiferromagnetic. SmNi4Sn2 shows the highest transition temperature of 55 K in this series of compounds. In PrNi4Sn2 and possibly NdNi4Sn2 there are two magnetic transitions.

DOI： 10.1143/JPSJ.66.235

Magnetoresistance, de Haas-van Alphen effect and Fermi surface of LaCu2 Reviewed

M Abliz, P Ahmet, D Aoki, Y Kimura, SK Dahr, R Settai, Y Onuki, H Harima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 66 ( 1 ) 194 - 199 1997.1

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

We have succeeded in growing a single crystal of LaCu2 and have done the electrical resistivity, magnetoresistance, de Haas-van Alphen effect and specific heat experiments. The Fermi surface is found to consist of three kinds of closed surfaces and a multiply-connected one, which are well explained by the FLAPW band calculations.

DOI： 10.1143/JPSJ.66.194

Anomalous field dependence of muon Knight shift and line width in the singlet ground state compound PrCu2 Reviewed

A Schenck, A Amato, FN Gygax, M Pinkpank, P Ahmet, M Ablitz, R Settai, Y Onuki

HYPERFINE INTERACTIONS 104 ( 1-4 ) 105 - 111 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：BALTZER SCI PUBL BV

We report on ZF and TF-studies of PrCu2 above the induced Jahn-Teller transition at 7.3 K. Generally a two-component signal is found, one showing inhomogeneous the other one homogeneous, temperature dependent line broadening. In ZF the former component is well represented by a Gaussian Kubo-Toyabe function with Delta similar or equal to 6.5 mu s(-1) at 7.5 K, corresponding to a field width of 76 G. This is about 30 times larger than what is calculated to arise from the Pr-141-nuclear dipole moments alone, pointing to strong hyperfine enhanced features. TF-field scans at 12 K revealed that the enhancement is suppressed in external fields exceeding 1 kG. In parallel the Knight shift drops from very large values well above 10% at 100 G to shifts of the order of 1% above 1 kG. A scaling of the Knight shifts with the corresponding relaxation rates seems to imply that the strange field dependence below 1 kG is associated with the magnetic susceptibility of the muons's nearest neighbour Pr3+-ions, a result for which we have no explanation yet to offer.

DOI： 10.1023/A:1012659306140

de Haas-van Alphen effect and the metamagnetic transition based on the quadrupole moment in PrCu2 Reviewed

M. Abliz, R. Settai, P. Ahmet, D. Aoki, K. Sugiyama, Y. Ōnuki

Philosophical Magazine B: Physics of Condensed Matter; Statistical Mechanics, Electronic, Optical and Magnetic Properties 75 ( 3 ) 443 - 462 1997

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

We have studied the metamagnetic transition in the Van Vleck paramagnetic compound PrCu2. This transition brings about an interchange between the easy (a) and the hard (c) axes’ directions of the magnetization which is reflected in drastic changes of the magnetoresistance and the de Haas-van Alphen oscillation. The origin of this metamagnetic transition is ascribed to the switching of the direction of the quadrupole moment in the 4f levels. © 1997 Taylor &amp
Francis Group, LLC.

DOI： 10.1080/13642819708202330

Search for a spontaneous magnetization in the superconducting B-phase of UPt3 Reviewed

H Kambara, T Yoshizumi, T Mamiya, N Kimura, R Settai, E Yammoto, Y Haga, Y Onuki

EUROPHYSICS LETTERS 36 ( 7 ) 545 - 549 1996.12

Language：English Publishing type：Research paper (scientific journal) Publisher：EDITIONS PHYSIQUE

We report the results of a search for a spontaneous magnetization in the superconducting B-phase of UPt3 which is predicted to exist because of broken time-reversal symmetry. We have measured the change of magnetic flux upon the superconducting transition in a field very close to zero by using a SQUID magnetometer. Our result gives the upper limit of 2 mG for the spontaneous internal held, one order of magnitude smaller than obtained by a recent mu SR measurement. The small value favors the theory of orbital degeneracy of the pair wave function over the theory of spin degeneracy.

DOI： 10.1209/epl/i1996-00267-5

Anisotropic magnetic response in the superconducting mixed state of UPt3 Reviewed

K Tenya, M Ikeda, T Tayama, T Sakakibara, E Yamamoto, K Maezawa, N Kimura, R Settai, Y Onuki

PHYSICAL REVIEW LETTERS 77 ( 15 ) 3193 - 3196 1996.10

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

Equilibrium magnetization M(eq) of the superconducting mixed state of UPt3 has been measured as a function of field. At low temperatures, the discontinuity of dM(eq)/dH at the upper critical field H-c2 exhibits marked anisotropy between the two principal directions of the hexagonal crystal, being indiscernibly small for H perpendicular to c, where the normal state paramagnetic susceptibility is largest. The results are not simply explained by the effective mass anisotropy nor by the ordinary paramagnetic effect of a spin-singlet pairing; they are rather in favor of an odd-parity pairing with an appreciable anisotropy in the pair-spin correlation.

DOI： 10.1103/PhysRevLett.77.3193

Magnetization Study of the Superconducting State of UPt<SUB>3</SUB> Reviewed

T. Sakakibara, K. Tenya, M. Ikeda, T. Tayama, H. Amitsuka, E. Yamamoto, K. Maezawa, N. Kimura, R. Settai, Y. Onuki

J. Phys. Soc. Jpn. 65 ( Suppl. B ) 202 - 208 1996.10

Odd Parity Superconducting State of UPt<SUB>3</SUB> Reviewed

H. Tou, Y. Kitaoka, K. Asayama, T. Sakakibara, K. tenya, M. Ikeda, H. Amitsuka, N. Kimura, R. Settai, Y. Onuki, E. Yamamoto, Y. Haga, K. Maezawa, K. Machida

固体物理 31 763 - 774 1996.9

Metamagnetic transition based on the quadrupole moment in PrCu2 Reviewed

R Settai, P Ahmet, M Abliz, K Sugiyama, Y Onuki, K Kindo, S Takayanagi

PHYSICA B-CONDENSED MATTER 223-24 ( 1-4 ) 389 - 391 1996.6

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

The metamagnetic transition of PrCu(2) brings about the crystal distortion based on the magnetoelastic effect. We have studied in detail this transition through the magnetostriction, magnetoresistance and magnetization measurements.

DOI： 10.1016/0921-4526(96)00131-7

Anomalous superconducting mixed state in single-crystalline CeRu2 Reviewed

H Goshima, T Suzuki, T Fujita, R Settai, H Sugawara, Y Onuki

PHYSICA B-CONDENSED MATTER 223-24 ( 1-4 ) 172 - 174 1996.6

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

The measurements of magnetization and ultrasonic velocity have been performed on single-crystalline CeRu(2) to clarify the anomalous superconducting mixed state on the basis of the FFLO state. Our experimental results suggest that a novel pinning mechanism works in the FFLO state.

DOI： 10.1016/0921-4526(96)00068-3

Fermi surface study of PrCu2, CeRu2Si2, CeRu2 and UPt3 Reviewed

Y Onuki, R Settai, H Aoki

PHYSICA B-CONDENSED MATTER 223-24 ( 1-4 ) 141 - 148 1996.6

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

We have done the de Haas-van Alphen (dHvA) experiments to clarify the Fermi surface properties such as Fermi surface, cyclotron mass and scattering lifetime of the conduction electrons for the highly correlated electron systems as in PrCu(2) with the singlet ground slate, a typical heavy Fermion compound CeRu(2)Si(2), a generalized FFLO superconductor CeRu(2) and an unconventional superconductor UPt(3).

DOI： 10.1016/0921-4526(96)00061-0

Fermi surface property of UPt3 studied by magnetoresistance and dHvA effect Reviewed

N Kimura, R Settai, Y Onuki, E Yamamoto, K Maezawa, H Aoki, H Harima

PHYSICA B-CONDENSED MATTER 223-24 ( 1-4 ) 181 - 184 1996.6

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

We have studied the Fermi surface property from the transverse magnetoresistance and de Haas-van Alphen (dHvA) experiments in UPt(3). These results have been discussed on the basis of the itinerant 5f band model.

DOI： 10.1016/0921-4526(96)00071-3

Anomalous pinning in superconductors with strong Pauli paramagnetism Reviewed

Y Onuki, M Hedo, Y Inada, R Settai, H Sugawara, Y Aoki, H Sato, M Deppe, P Gegenwart, C Geibel, M Lang, T Luhmann, R Modler, M Weiden, F Steglich, C Paulsen, JL Tholence, N Sato, T Komatsubara, M Tachiki, S Takahashi

PHYSICA B-CONDENSED MATTER 223-24 ( 1-4 ) 28 - 32 1996.6

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

The results of the magnetization, magnetostriction and AC-susceptibility experiments are presented for both the antiferromagnetic heavy-Fermion superconductor UPd(2)Al(3) and the valence fluctuation compound CeRu(2). For (H > 10 kOe). These results are discussed on the basis of a generalized Fulde-Ferrell-Larkin-Ovchinnikov superconducting state.

DOI： 10.1016/0921-4526(96)00030-0

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