研究者詳細 - 武田　直也

論文 - 武田　直也

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Superconducting gap of the single crystal beta-PdBi2 査読

H.Matsuzaki, K.Nagai, N.Kase, T.Nakano, N.Takeda

J.Phys. : Conf.Series 871 012001-1 - 012001-5 2017年7月

Heavy-Fermion Compound of the ternary Phosphide Ce2Pt8P with a Non-Cencentrosymmetric Structure, 査読

N.Kase, Shoh Furukawa, T.Nakano, N.Takeda

J.Phys.Soc.Jpn. 86 ( 1 ) 014704-1 - 014704-4 2017年1月

CePtGe<sub>2</sub>の試料作成とその基礎物性

大沼翔馬, 山口嵩人, 加瀬直樹, 中野智仁, 武田直也, 上床美也

日本物理学会講演概要集 72 ( 0 ) 2150 - 2150 2017年

記述言語：日本語出版者・発行元：一般社団法人日本物理学会

<p>CePtGe_2_は, はじめ, Pecharskyらによって多結晶試料を用いた物性測定が行われ, その後, Kiritaらが多結晶および単結晶試料を作成し測定を行ったが, それぞれの報告には相違があった。本研究ではCePtGe_2_の多結晶および単結晶を新たに作成し, CePtGe_2_の物性を明らかにすることを目的とした。我々は, CePtGe_2_の多結晶試料をアーク融解によって作成し, 単結晶試料はBiフラックス法を用いて育成を行った。実験結果などの詳細は当日に示す。</p>

DOI： 10.11316/jpsgaiyo.72.1.0_2150

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Superconductivity in Y6Tr4Al43 (Tr = Nb, Mo, Ta) with Peanut-Shaped Cage Structure 査読

Naoki Kase, Ryoh Satoh, Tomohito Nakano, Naoya Takeda

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 85 ( 10 ) 105001-1 - 105001-2 2016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：PHYSICAL SOC JAPAN

Superconductivity is discovered in Y6Tr4Al43 (Tr = Nb, Mo, Ta) with a peanut-shaped cage structure at T-c = 0.86, 0.75, and 0.68 K, respectively. The superconducting state is revealed by performing electrical resistivity and specific heat measurements. The upper critical field is obtained to be 0.22 (Nb), 0.175 (Mo), and 0.15 T (Ta). A specific heat jump provides evidence of bulk superconductivity in these compounds.

DOI： 10.7566/JPSJ.85.105001

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Thermal Conductivity Measurements of Caged Structural Superconductors 査読

H. Matsuzaki, K. Hida, N. Kase, T. Nakano, N. Takeda

PHYSICS PROCEDIA ( 81 ) 61 - 64 2016年5月

Superconducting and Normal State Properties in the Ternary Silicide NbIrSi, TaIrSi, and NbPtSi 査読

H. Suzuki, N. Kase, T. Nakano, N. Takeda

PHYSICS PROCEDIA ( 81 ) 57 - 60 2016年5月

Single crystal growth and superconducting properties of LaO0.5F0.5Bi(S0.8Se0.2)2 査読

Y. Terui, K. Saitoh, N. Kase, T. Nakano, N. Takeda

PHYSICS PROCEDIA ( 81 ) 53 - 56 2016年5月

Superconductivity in Ternary Pnictide SrPd2Sb2 Polymorphs 査読

Naoki Kase, Harufumi Suzuki, Takenori Tsukamoto, Tomohito Nakano, Naoya Takeda

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 85 ( 4 ) 043701-1 - 043701-5 2016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：PHYSICAL SOC JAPAN

Superconductivity was observed in SrPd2Sb2 polymorphs: a primitive tetragonal CaBe2Ge2-type (low-temperature phase, LT-SrPd2Sb2) structure and body-centered ThCr2Si2-type (high-temperature phase, HT-SrPd2Sb2) structure. The superconducting transition was observed at T-c = 1.95 (LT) and 0.6K (HT). The specific heat C(T) showed a clear anomaly at T-c = 1.85 (LT) and 0.6K (HT); thus, the superconductivity was of a bulk nature. The agreement with the Bardeen-Cooper-Schrieffer (BCS) curve indicated that the LT-SrPd2Sb2 superconductor was fully gapped. The values of electron-phonon coupling lambda(ep) and density of state at Fermi level N(E-F) in 122 compounds with the CaBe2Ge2-type and its related structure were evaluated to reveal the main factor that determines T-c. From our systematic analysis, T-c of this family can be explained by lambda(ep) rather than N(E-F).

DOI： 10.7566/JPSJ.85.043701

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Superconductivity in the ternary silicide TrIrSi (Tr = Ti, Zr, and Hf) 査読

Naoki Kase, Harufumi Suzuki, Tomohito Nakano, Naoya Takeda

SUPERCONDUCTOR SCIENCE & TECHNOLOGY 29 ( 3 ) 035011 2016年3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：IOP PUBLISHING LTD

We discover a new superconductor, TiIrSi at T-c = 1.4 K, and reveal a superconducting state of TrIrSi (Tr = Ti, Zr, and Hf) by using dc magnetic susceptibility chi(T), electrical resistivity rho(T), and specific heat C(T) measurements. Superconductivity of TrIrSi is confirmed in rho(T) at T-c = 1.4, 1.85, and 3.4 K, respectively. The electronic specific heat C-e(T) of TrIrSi can be fitted with the theoretical BCS curve of the weak-coupling limit with Delta C-e/gamma T-c = 1.43. Measurements in several magnetic fields suggest that TrIrSi is a type-II superconducting material with upper critical fields of mu H-0(c2)(0) = 0.751, 0.618, and 2.23 T, respectively. The electron-phonon coupling constants lambda(ep) are calculated to be 0.441, 0.464, and 0.545, which are consistent with the weak- coupling limit inferred from the specific jump. The T-c of TrIrSi depends on lambda(ep) and is inversely proportional to N(E-F).

DOI： 10.1088/0953-2048/29/3/035011

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Low temperature superconducting phase of the ternary pnictide SrPd2Sb2 with CaBe2Ge2-type structure 査読

N. Kase, H. Suzuki, T. Tsukamoto, T. Nakano, N. Takeda

JOURNAL OF PHYSICS-CONFENCE SERIES ( 683 ) 012034 2016年2月

Low temperature properties of ZrTr2Zn20 (Tr = transition metal) with a pyrochlore lattice 査読

S. Hasegawa, K. Morihiro, N. Kase, T. Nakano, N. Takeda

JOURNAL OF PHYSICS-CONFENCE SERIES ( 683 ) 012021 2016年2月

Low-temperature study of the Sm-based compound SmOs2Zn20 査読

M. Tanahashi, K. Adachi, T. Sasahara, N. Kase, T. Nakano, N. Takeda

JOURNAL OF PHYSICS-CONFENCE SERIES ( 683 ) 012019 2016年2月

NMR studies on polyphosphide Ce6Ni6P17 査読

T. Koyama, H. Yamada, K. Ueda, T. Mito, Y. Aoyama, T. Nakano, N. Takeda

Journal of Physics: Conference Series 683 ( 1 ) 12027 2016年

Antiferromagnetic transition of the caged compound TmTi2Al20 査読

Naoki Kase, Yasuyuki Shimura, Shunichiro Kittaka, Toshiro Sakakibara, Satoru Nakatsuji, Tomohito Nakano, Naoya Takeda, Jun Akimitsu

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS 2014 (SCES2014) 592 012052-1 - 012052-5 2015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 examined the low temperature magnetic properties of a single crystal of TmTi2Al20, a hole analogue of PrTi2Al20, by means of specific heat C(T) and magnetization M(T, H) measurements. At low field, an anomaly that can be ascribed to an antiferromagnetic ordering is observed in M(T) at T-N = 0.7 K. C(T) shows a very sharp lambda-type anomaly at 0.7 K, confirming the phase transition. From the calculated magnetic entropy S(T), we found that the ground state of TmTi2Al20 is likely to be a magnetic Gamma(5) triplet in the J = 6 multiplet.

DOI： 10.1088/1742-6596/592/1/012052

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Magnetic ordering of hyperfine-coupled nuclear and 4f -electron moments in the clathrate compound Pr3Pd20Ge6. 査読

O. Iwakami, Y. Namisashi, S. Abe, K. Matsumoto, G. Ano, M. Akatsu, K. Mitsumoto, Y. Nemoto, N. Takeda, T. Goto, H. Kitazawa

PHYSICAL REVIEW B 90 ( 10 ) 100402-1 - 100402-5 2014年9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：AMER PHYSICAL SOC

Complex ac susceptibility, chi = chi' - i chi '', measurements of the clathrate compound Pr3Pd20Ge6 were performed in static fields up to 10 mT for H parallel to [001] and at temperatures down to 500 mu K. Praseodymium (Pr) nuclear magnetic moments at the 8c site, where quadrupole moments of 4f electrons order at T-Q1 = 250 mK, were found to order antiferromagnetically at 9 mK, as shown by a peak in chi' and a substantial increase in thermal relaxation time. The large enhancement factor (1 + K-8c) obtained by calculation of the hyperfine-enhanced nuclear susceptibility of Pr at the 8c site accounts for the high transition temperature of Pr nuclear magnetic moments and the large chi' below 30 mK. From analysis of the crystalline electric field and the mean-field approximation, we conclude that a chi peak at 77 mK can be ascribed to an antiferromagnetic ordering of magnetic moments of 4f electrons at the 4a site. We found that nuclear and f-electron moments order separately on two sublattices in this compound. The temperature and magnetic field dependence of chi' and chi '' between 30 and 60 mK are discussed in terms of dissipation phenomena.

DOI： 10.1103/PhysRevB.90.100402

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Another phase transition beside superconductivity in skutterudite LaOs4P12

N.Takeda, N.Hoshi, S. Yodono, R.Takeda, N.Kurotaki, T.Nakano

JPS Conf.Proc. 3 017024-1 - 017024-5 2014年7月

Vibrational dynamics of filled skutterudites LaT4X 12(T = Fe, Ru, Os, X = As, Sb) 査読

Michael Marek Koza, Devashibhai Adroja, Naoya Takeda, Zygmunt Henkie, Tomasz Cichorek

Journal of the Physical Society of Japan 82 ( 11 ) 114607/1 - 11 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report on the vibrational properties of the lanthanum filled skutterudite compounds LaRu4Sb12, LaOs4Sb 12, and LaOs4As12studied by inelastic neutron scattering. The experimental data are backed up by ab initio lattice dynamics calculations of the complete series of lanthanum filled skutterudites LaT 4X12with T = Fe, Ru, Os and X = As, Sb. We present details of their structural properties, phonon dispersion relations, vibrational densities of states Z(w) and specific heats CV(T) calculated from Z(w) within the harmonic approximation. Powder averaged lattice dynamics (PALD) technique is applied to approximate the experimental signal presented as the generalized density of states G(w) with high accuracy. Furthermore, the PALD approach is exploited to compute average transverse vtPALD and longitudinal v1PALD sound velocities, elastic constants c11 PALD, c44 PALD, bulk moduli B PALD, and Debye temperatures θD ALD. The PALD results are compared with data computed from ab initio lattice dynamics calculations. All calculated properties are in very good agreement with literature data. © 2013 The Physical Society of Japan.

DOI： 10.7566/JPSJ.82.114607

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Intermediate valence behavior of Yb2Ni12P7 studied by using 31P NMR 査読

T. Koyama, K. Sugiura, K. Ueda, T. Mito, T. Kohara, R. Satoh, K. Tsuchiya, T. Nakano, N. Takeda

Journal of the Korean Physical Society 63 ( 3 ) 416 - 419 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

The Yb-based heavy-fermion compound Yb2Ni12P7 with a hexagonal Zr2Fe12P7-type crystal structure was investigated by using the 31P nuclear magnetic resonance (NMR) technique. The complicated NMR line changes its shape gradually with decreasing temperature, implying the presence of some Knight shift components. The temperature dependences of the Knight shift and the nuclear spin-lattice relaxation rate 1/T 1 suggest the delocalization of 4f electrons. © 2013 The Korean Physical Society.

DOI： 10.3938/jkps.63.416

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Low-temperature magnetic properties of RE2Ni21B 6 (RE = Er, Tm, Yb and Lu) 査読

J. Kitagawa, N. Takeda, M. Ishikawa

Journal of Alloys and Compounds 561 101 - 104 2013年6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 Ltd

The low-temperature magnetic properties of RE2Ni 21B6 (RE = Er, Tm, Yb and Lu) crystallizing into a cubic C6Cr23-type structure were investigated by measuring magnetic susceptibility, electrical resistivity and specific heat. An off-stoichiometric Er compound with a single phase undergoes antiferromagnetic ordering at 0.61 K. Tm and Yb compounds have no magnetic ordering down to 50 mK. The 4f-electron ground state under a cubic crystalline electric field was deduced by the analysis of the specific heat for each magnetic compound. Tm 2Ni21B6 is considered to have the non-Kramers T3-doublet ground state with a quadrupolar moment. The quadrupolar moment does not show a long-range order, but probably enters into a glass state owing to the presence of atomic disorder. Our study suggests that atomic disorder degrades the long-range nature of quadrupolar interactions. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2013.01.073

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Magnetic phase diagram of clathrate compound Ce3Pd20Si6 with quadrupolar ordering 査読

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

JOURNAL OF PHYSICS-CONDENSED MATTER 25 ( 12 ) 126003-1 - 4 2013年3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：IOP PUBLISHING LTD

We present results of specific heat measurements on a Ce3Pd20Si6 single crystal and construct the magnetic phase diagram for the three cubic principal directions [100], [110] and [111]. The highly anisotropic phase diagram is discussed and can be qualitatively explained by the Zeeman splitting at the 8c-site. For B parallel to [100], the present study found two different quadrupolar ordered phases, which meet the paramagnetic phase at a tri-critical point and establish the new phase boundaries.

DOI： 10.1088/0953-8984/25/12/126003

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