研究者詳細 - 武田　直也

Quadrupole Ordering and Rattling Motions in Clathrate Compound Pr3Pd20Ge6 査読

G.Ano, T.Yamaguchi, K.Araki, K.Matsuo, Y.Tachikawa, K.Mitsumoto, M.Akatsu, Y.Nemoto, T.Goto, N.Takeda, A.Donni, H.Kitazawa

J.Phys.Soc.Jpn. 81 034710-1 - 034710-11 2012年3月

Pressure effect of transport properties of hexagonal Yb2Ni12P7 査読

Tomohito Nakano, Ryohei Satoh, Katsuhiko Tsuchiya, Naoya Takeda, Kazuyuki Matsubayashi, Yoshiya Uwatoko

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 012054-1 - 012054-2 2012年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We prepared single crystals of Yb2Ni12P7 using a Sn-flux method and measured their resistivity under hydrostatic pressure up to 8 GPa. At ambient pressure, the magnetic part of resistivity rho(mag)(T) shows a peak around T-max similar to 100 K and T-2 dependence below the characteristic temperature of the Fermi liquid, T-FL = 3 K. When pressure increases up to 2.06 GPa, the value of rho(mag)(T) above T-max decreases slightly but rho(mag) below T-max increases slightly. TFL decreases with increasing pressure, and is expected to become zero at 2.5 GPa. Around this pressure, the coefficient of T-2 in rho(mag) significantly increases, suggesting the existence of a quantum critical point. Above 2.5 GPa, overall rho(mag) gradually decreases with increasing pressure up to 6 GPa, but it below 15.5 K increases above 6 GPa.

DOI： 10.1088/1742-6596/391/1/012052

Specific heat of Ce3Pd20Si6 single crystal in magnetic fields 査読

H. Ono, T. Nakano, N. Takeda, G. Ano, M. Akatsu, Y. Nemoto, T. Goto, H. Kitazawa

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 012054-1 - 012054-4 2012年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We report the specific heat measurement of single crystalline Ce3Pd20Si6 and the resultant magnetic phase diagram for the direction of B//[100]. In zero field, we confirmed two successive phase transitions at T = 0.24 K and 0.4 K. The magnetic phase diagram clearly shows a phase boundary of paramagnetic phase I, quadrupole ordered phase II and II'.

DOI： 10.1088/1742-6596/391/1/012054

Physical properties of unfilled skutterudite NiP3 査読

N. Takeda, T. Nakajo, H. Ono, K. Tatematsu, T. Nakano

Journal of the Physical Society of Japan 80 SA035-1 - SA035-2 2011年7月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

We succeeded to prepare large single crystals. We present the electrical resistivity, the magnetic susceptibility and the low-temperature specific heat measurements of unfilled skutterudite NiP3. The temperature dependence of the electrical resistivity of NiP3 is metallic and the residual resistivity ratio, RRR, is estimated to be about 30. No superconductivity was found down to 0.078 K. The magnetic susceptibility shows weakly temperature dependent Pauli paramagnetism. The electronic specific-heat coefficient was determined to be 8.0 mJ/mole·K2. © 2011 The Physical Society of Japan.

DOI： 10.1143/JPSJS.80SA.SA035

The magnetic moment without magnetic phase transition in insulating RR'S3(R=La, Ce, Pr, Nd; R'=Yb, Lu) 査読

Hiroki Ono, Tatsuya Kuwahara, Tatsuya Furui, Kenji Tatematsu, Tomohito Nakano, Naoya Takeda

Journal of the Physical Society of Japan 80 SA079-1 - SA079- 2011年7月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

We have synthesized RR'S3(R=La, Ce, Pr, Nd
R'=Yb, Lu) by a flux method, with a flux of potassium iodide, KI, and have measured the magnetic susceptibility and specific heat. The magnetic susceptibility of LaYbS3, CeYbS3, CeLuS3, PrLuS3 and NdLuS3 follows a Curie-Weiss law at high temperatures. From the slope of χ-1 versus T, we evaluate the valence of all rare-earth elements to be trivalent. LaYbS3, CeYbS3, CeLuS3, and PrLuS3 show no clear magnetic transition, while NdLuS3 shows one at 0.25 K. © 2011 The Physical Society of Japan.

DOI： 10.1143/JPSJS.80SA.SA079

Low-temperature magnetic properties of Ho2Ni12P7 査読

Katsuhiko Tsuchiya, Atsumi Ohashi, Takahumi Nashimoto, Hiroki Ono, Kenji Tatematsu, Tomohito Nakano, Naoya Takeda

Journal of the Physical Society of Japan 80 SA081-1 - SA081-2 2011年7月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

We present the magnetic susceptibility and low-temperature specific-heat of Ho2Ni12P7. The magnetic susceptibility of Ho2Ni12P7 follows a Curie-Weiss law down to 10 K. Ho2Ni12P7 orders antiferromagnetically below Néel temperature TN = 10 K. The magnetization exhibits a metamagnetic behavior below TN. The specific-heat shows a clear peak due to the transition. The crystalline-field ground state of Ho2Ni12P7 is a doublet. © 2011 The Physical Society of Japan.

DOI： 10.1143/JPSJS.80SA.SA081

Electric field gradient fluctuations in filled skutterudite ReRu 4Sb12 (Re = La, Ce and Pr) probed by Sb-NQR 査読

Mamoru Yogi, Haruo Niki, Hitoshi Sugawara, Naoya Takeda, Hideyuki Sato

Journal of the Physical Society of Japan 80 SA027-1 - SA027-3 2011年7月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

We have carried out 121,123Sb nuclear quadrupole resonance (NQR) measurements on ReRu4Sb12 (Re = La, Ce and Pr) to investigate an anomalous behavior of the nuclear spin-echo relaxation rate 1/T2 observed in ReOs4Sb12. The full width at half maximum of the NQR spectrum shows a step-like increase below 130 K with decreasing temperature. Temperature dependence of 1/T2 also shows a divergence at ∼115 K whereas the nuclear spin-lattice relaxation rate 1/T1 does not show any anomaly. These results are caused by a distribution of the electric field gradient (EFG) and its fluctuations, which might arise from a rattling motion of the rare earth ion centered in the cage which consists of twelve Sb and/or a small deformation of the cage. The EFG fluctuations observed in ReOs4Sb12 and ReRu 4Sb12 at T ∼ 120 K originates from an unique crystal structure of the filled skutterudite with oversized Sb-cage. © 2011 The Physical Society of Japan.

DOI： 10.1143/JPSJS.80SA.SA027

Seebeck coefficient for concentrated Kondo compound CePtSi2 under hydrostatic pressure 査読

T.Nakano, S.Yonamine, M.Hedo, T.Nakama, M.Ohashi, N.Takeda, G.Oomi

J.Phys.Soc.Jpn. 80 SA028-1 - SA028-2 2011年6月

Quadrupole Ordering and Rattling in Clathrate Compound Pr3Pd20Ge6 査読

G. Anol, K. Matsuo, K. Araki, Y. Tachikawa, K. Mitsumoto, M. Akatsu, Y. Nemoto, T. Goto, N. Takeda, A. Kikkawa, A. Doenni, H. Kitazawa

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2010) 273 012002-1 - 012002-2 2011年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We have studied quadrupole ordering and rattling in clathrate compound Pr3Pd20Ge6 using ultrasonic measurements. The softening were observed in temperature dependence of elastic constants C-11, (C-11 - C-12)/2 and C-44. The C-11 and (C-11 - C-12)/2 show minimums at 250 mK indicating a transition point to an antiferroquadrupole ordered phase due to a F3 doublet ground state at 8c site. Furthermore, the C-11, (C-11 - C-12)/2 and C-44 exhibit discontinuitive anomalies at 60 mK revealing a ferroquadrupole ordering due to a F-5 triplet ground state at 4a site. Two distinctive ultrasonic dispersions caused by thermally activated F-5-type rattling were observed in C-44 around 15 K and 25 K.

DOI： 10.1088/1742-6596/273/1/012002

Quadrupole Order in Clathrate Compound Pr3Pd20Si6 査読

M. Akatsu, S. Tsuduku, Y. Nemoto, T. Goto, I. Ishii, K. Mitsumoto, G. Ano, H. Kobayashi, N. Takeda, A. Doenni, H. Kitazawa

INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 012121-1 - 012121-4 2010年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

In order to investigate ordered phases revealed at low temperatures in clathrate compound Pr3Pd20Si6, we have performed ultrasonic measurements using a single crystal in magnetic fields at low temperatures. Temperature dependence of elastic constant C-11 and C-L[1 (1) over bar0] = (C-11 + C-12 + C-2(44))/2 shows the anomalies at about 150 mK in zero field. Magnetic phase diagrams are determined by measuring C-11 in H parallel to [001] and C-L[1 (1) over bar0] in H parallel to [111]. The magnetic phase diagrams along the three principal axes indicate a closed loop and a strong magnetic anisotropy. This result suggests that antiferroquadrupole ordering appears at low temperatures in Pr3Pd20Si6.

DOI： 10.1088/1742-6596/200/1/012121

Ultrasonic investigation of off-center rattling in Pr0.55Nd0.45Os4Sb12 査読

Tatsuya Yanagisawa, Taichi Mayama, Hiroyuki Hidaka, Hiroshi Amitsuka, Akio Yamaguchi, Koji Araki, Yuichi Nemoto, Terutaka Goto, Naoya Takeda, Pei-Chun Ho, M. Brian Maple

PHYSICA B-CONDENSED MATTER 404 ( 19 ) 3235 - 3237 2009年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Ultrasonic measurements on a Pr0.55Nd0.45Os4Sb12 single crystal for temperature down to 20mK and frequencies up to 245 MHz were performed in order to investigate off-center rattling motion of rare-earth ions. The elastic constant C-11 exhibits double ultrasonic dispersions at similar to 15 and similar to 40 K, which are similar to the features found in NdOs4Sb12. The estimated activation energy E-1 = 240 K corresponding to the 40 K-dispersion, possesses an intermediate value between PrOs4Sb12 (E-1 = 115 K) and NdOs4Sb12 (E-1 = 337 K). (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2009.07.081

Quadrupole Ordering in Clatherate Compound Ce3Pd20Si6<共著> 査読

T.Goto, T.Watanabe, S.Tsuduku, H.Kobayashi, Y.Nemoto, T.Yanagisawa, M.Akatsu, G.Ano, O.Suzuki, N.Takeda, A.Donni, H.Kitazawa

J.Phys.Soc.Jpn. 78 ( 2 ) 024716-1 - 024716-9 2009年2月

Low temperature x-ray diffraction study on superconductivity 査読

Y. Xue, H. Kaneko, Q. Tao, Z. Xu, N. Takeda, Y. Nemoto, T. Goto, H. Suzuki

25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PT 5A 150 ( 5a ) 052284-1 - 052284-4 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

Using a low temperature x-ray diffractometer, we studied superconductivity materials, optimally doped and underdoped YBCOs and PrOs(4)Sb(12) between 0.1 K and 300 K. At several temperatures, whole profiles of the x-ray reflection peak were measured and refined by Rietveld analysis. By Rietveld analysis, we found that Pr atoms in PrOs(4)Sb(12) are still oscillating at an amplitude of about 0.1 angstrom at 0.18 K. For some reflection planes, x-ray diffraction measurement with a small step size and a long stepping time was performed to accumulate more counts at certain temperatures. The lattice constant d of optimally doped YBCO (OPT YBCO) shows anomalous behaviours at around the superconductivity transition temperature Tc and around spin gap temperature T*. In OPT YBCO, the intensity of the reflection spectrum shows a clear anomaly at around Tc.

DOI： 10.1088/1742-6596/150/5/052284

Inelastic neutron scattering study of spin gap formation in heavy fermion compounds 査読

D. T. Adroja, K. A. Mcewen, J. -G. Park, A. D. Hillier, N. Takeda, P. S. Riseborough, T. Takabatake

JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS 10 ( 7 ) 1564 - 1582 2008年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATL INST OPTOELECTRONICS

According to conventional theories of strongly correlated electron systems, the natural consequence of strong hybridization between f-electrons and conduction electrons is the opening of a gap in both charge and spin channels. Despite their importance, there are few experimental observations of such gaps in real materials. Recently the charge gap in d- and f-electron systems has been investigated using optical studies. However, due to the q=0 limitation of the technique, optical studies cannot give information on the wave vector dependence of the gap. Inelastic neutron scattering is a unique technique and provides direct information on the spin gap energy as well as its wave vector and temperature dependence. Further, knowledge of the wave vector dependence of the gap, in particular the spin gap, provides important information about the microscopic mechanism of the gap formation. Recently we have investigated the spin gap formation, and its relation to the charge gap, in several Ce, Yb and U based compounds using inelastic neutron scattering techniques. We review here the nature of the spin gap in CeT4Sb12 (T = Ru, Os and Fe), CeRhAs and U2-xThxRu2Sn compounds based on our recent neutron scattering studies. We compare the magnitude of the spin gaps we have measured in this way with that of the charge gaps measured in optical studies. We have found a universal scaling relation between the spin gap energy and the Kondo temperature (T-K) for many strongly correlated electron systems and the results are discussed.

NQR Study of Filled Skutterudite CeT4Sb12(T=Ru and Os) 査読

M.Yogi 他

J.Phys.Soc.Jpn.,Supple.A 77 321 - 323 2008年6月

Heavy Fermion Behaviors of Tm2Rh12P7 査読

K.Tatematsu, N.Takeda 他

J.Phys.Soc.Jpn.,Supple.A 77 353 - 355 2008年6月

Guest Ion Motion in Cage Structure Crystals Investigated by Raman Scattering 査読

M.Udagawa, T.Hasegawa, Y.Takasu, N.Ogita, K.Suekuni, M.A.Avila, T.Takabatake, Y.Ishikawa, N.Takeda

J.Phys.Soc.Supple.A 77 142 - 147 2008年4月

NQR investigation on multipolar ordering systems 査読

T. Mito, S. Tomisawa, S. Masaki, M. Takemura, S. Wada, H. Harima, Y. Kato, M. Kosaka, D. Kikuchi, H. Sato, H. Sugawara, N. Takeda, G. -q. Zheng

PHYSICA B-CONDENSED MATTER 403 ( 5-9 ) 1633 - 1635 2008年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We have carried out nuclear quadrupolar resonance (NQR) measurements on SmRu4P12 and YbAl3C3, both of which have attracted much interest in terms of multipolar ordering. Although no structural anomalies have been detected by diffraction experiments so far, the NQR resonance frequencies v(Q)'s of both compounds show marked anomalies just below each phase transition temperature, which probably probes the order parameters. The results provide important information to shed light on the ordered structures in the low temperature phases of these compounds. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2007.10.206