Faculty Profiles - NAKANO Tomohito

Papers - NAKANO Tomohito

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Heavy-Fermion Compound of the Ternary Phosphide Ce2Pt8P with a Non-Centrosymmetric Structure Reviewed

Naoki Kase, Shoh Furukawa, Tomohito Nakano, Naoya Takeda

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 ( 1 ) 2017.1

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

The low-temperature properties of Ce2Pt8P are studied by magnetic susceptibility chi(T), electrical resistivity rho(T), and specific heat C(T) measurements. The crystal structure is considered to be analogs of the CePt3Si-type structure. From the magnetic susceptibility chi(T), the effective paramagnetic moment mu(eff) is estimated to be 2.30 mu(B)/Ce, suggesting that the valence state of Ce ions is expected to be close to trivalent (Ce3+). The paramagnetic Curie-Weiss temperature theta cw is determined to be 12 K. The electrical resistivity rho(T) shows -ln T dependence with a small slope from 10 to 3K, which indicates a weak Kondo anomaly. The specific heat exhibits a lambda-type anomaly at around T* = 1.0 K, while the magnetic entropy at T* is reduced to 80% of R ln 2. The linear coefficient of specific heat is determined to be 145 mJ=(mol-Ce.K-2). From several measurements, Ce2Pt8P can be classified as a moderate heavy-fermion compound. The ground state is far from the quantum-critical point (QCP) compared with CePt3Si. La2Pt8P shows normal metallic behavior and no superconductivity is observed above 0.28 K.

DOI： 10.7566/JPSJ.86.014704

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

Naoki Kase, Ryoh Satoh, Tomohito Nakano, Naoya Takeda

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 85 ( 10 ) - 105001 2016.10

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

Superconductivity in Ternary Pnictide SrPd2Sb2 Polymorphs Reviewed

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 85 ( 4 ) - 43701 2016.4

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

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

Naoki Kase, Harufumi Suzuki, Tomohito Nakano, Naoya Takeda

SUPERCONDUCTOR SCIENCE & TECHNOLOGY 29 ( 3 ) 35011 2016.3

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

NMR studies on polyphosphide Ce6Ni6P17 Reviewed

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

Journal of Physics: Conference Series 683 ( 1 ) 12027 2016.2

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Physics Publishing

We report the result of 31P nuclear magnetic resonance (NMR) studies on Ce6Ni6P17. The observed NMR spectra show a Lorentzian-type and an asymmetric shapes, reflecting the local symmetry around each P site in the cubic unit cell. We have identified the observed NMR lines corresponding to three inequivalent P sites and deduced the temperature dependence of the Knight shift for each site. The Knight shifts increase with decreasing temperature down to 1.5 K, indicating a localized spin system of Ce6Ni6P17. Antiferromagnetic correlation between 4f spins is suggested from the negative sign of the Weiss-temperature.

DOI： 10.1088/1742-6596/683/1/012027

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

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

JOURNAL OF PHYSICS-CONFENCE SERIES ( 683 ) 012021 2016.2

Single-crystal growth and superconducting state of LaO0.5F0.5Bi(S0.8Se0.2)(2) Reviewed

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

PROCEEDINGS OF THE 28TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2015) 81 53 - 56 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

Single crystals of LaO0.5F0.5Bi(S0.8Se0.2)(2) were grown by a CsCl-flux method. Electrical resistivity rho(T) measurements were performed to reveal its superconducting properties. The rho(T) of the single crystal shows semiconducting-like behavior and superconducting transition at 3.4 K. The value is slightly higher than that of the polycrystalline sample with substitution amounts of x = 0.2 (T-c similar to 2.5 K). From rho(T) measurements in several magnetic fields, mu H-0(c2)//ab(0) and mu H-0(c2)//c(0) are estimated to be 17.2 T and 0.59 T, respectively. The superconducting anisotropic parameter gamma is determined to be 29.2. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2016.04.023

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

Harufumi Suzuki, Naoki Kase, Tomohito Nakano, Naoya Takeda

PROCEEDINGS OF THE 28TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2015) 81 57 - 60 2016

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

The polycrystalline NbIrSi, TaIrSi and NbPtSi with an orthorhombic structure (space group Pnma) were synthesized by an arc-melting method. Electrical resistivity rho(T) measurement in three compounds were performed from 0.28 to 300 K. rho(T) of NbIrSi indicates typical metallic behavior with no superconducting transition down to 0.28 K. Superconducting-like behavior is observed around 0.5 K in TaIrSi, but zero resistivity cannot be observed down to 0.28 K. rho(T) of NbPtSi shows superconductivity at 1.24 K. From rho(T) in several magnetic fields, the upper critical field mu H-0(c2)(0) of NbPtSi is obtained to be 1.15 T. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2016.04.024

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

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

TMU INTERNATIONAL SYMPOSIUM ON NEW QUANTUM PHASES EMERGING FROM NOVEL CRYSTAL STRUCTURE 683 - 12034 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

We find that low temperature superconducting phase (LSP) of SrPd2Sb2 with the CaBe2Ge2-type structure at T-c = 1.4 K. Superconducting transition is found at T-c = 1.4 K in electrical resistivity rho(T). Specific heat C(T) shows a clear anomaly at T-c = 1.2 K, which shows that superconductivity is of bulk nature. From rho(T) in several magnetic fields, the upper critical field mu 0IIc2(0) is estimated to be 36 mT, which is strongly suppressed, and is 16.7 times smaller than that of 1.9 K phase.

DOI： 10.1088/1742-6596/683/1/012034

Thermal Conductivity Measurements of Caged Structural Superconductors Reviewed

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

PROCEEDINGS OF THE 28TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2015) 81 61 - 64 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

Thermal conductivity of Ca3Rh4Sn13 and Sr3Ir4Sn13 were measured in magnetic fields to reveal superconducting state. From magnetic susceptibility chi(T) and electrical resistivity rho(T) measurements, superconducting transition temperature T-c of Ca3Rh4Sn13 and Sr3Ir4Sn13 is determined to be 8 and 5 K, respectively. Thermal conductivity kappa(T) of Ca3Rh4Sn13 indicates that superconducting state is nodeless s-wave, because residual thermal conductivity kappa(0)/T in zero magnetic field is very small. On the other hand, kappa(T) of Sr3Ir4Sn13 in zero magnetic field suggests that superconductivity possesses nodal gap rather than full gap. Whether nodal superconducting gap exists or not still remains to be clarified, because there is a possibility that the achieving temperature is insufficient to discuss superconducting state. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2016.04.025

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

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

TMU INTERNATIONAL SYMPOSIUM ON NEW QUANTUM PHASES EMERGING FROM NOVEL CRYSTAL STRUCTURE 683 - 12019 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

We synthesized single crystals of Zn-based Sm-compound SmOs2Zn20. T-dependence of magnetization M(T) shows a sudden increase at the ferromagnetic transition temperature T-C similar to 3 K. T-dependence of electrical resistivity rho(T) shows typical metallic behavior. At T-C, rho(T) slightly decreases, which originates from the ferromagnetic transition. Specific heat C(T) shows a clear but broad anomaly at T-C. Magnetic entropy S-mag(T) at T-C is about R ln 2, and suggests that a Gamma(7) doublet of the J = 5/2 multiplet is the ground state.

DOI： 10.1088/1742-6596/683/1/012019

Pressure-induced novel electronic state of Fe70Ni30 Invar alloy Reviewed

Gendo Oomi, Ryohei Saito, Masashi Ohashi, Tomohito Nakano

20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015 75 785 - 791 2015

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

The electrical resistance and magnetoresistance of Fe70Ni30 Invar alloy have been measured at high pressure up to 15 GPa. It is found that the coefficients of T-2 term in the electrical resistance increases with increasing pressure but tends to saturate above 12 GPa suggesting a peak above 15 GPa, which implies a pressure-induced quantum phase transition. We found for the first time that the magnetoresistance at 4.2 K is negative below 11 GPa but becomes positive above 12 GPa. This corresponds to a crossover in the electronic state from localized moment regime to a paramagnetic or new magnetic state. The origins will be discussed briefly in connection with the recent experimental results and theoretical calculation.

DOI： 10.1016/j.phpro.2015.12.102

Antiferromagnetic transition of the caged compound TmTi2Al20 Reviewed

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 - 12052 2015

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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

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 2014.7

Thermal and Magnetic Properties in Ce1-xErxAl2 Intermetallic Compounds Reviewed

Masashi Ohashi, Hidenori Miyagawa, Tomohito Nakano, Gendo Oomi, Vladimir Sechovsky, Isamu Satoh, Takemi Komatsubara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 83 ( 2 ) 2014.2

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

The magnetic and thermal properties of Ce1-xErxAl2 compounds have been studied using specific heat, dc magnetization, and ac susceptibility measurements. All these compounds are isomorphic with the MgCu2 Laves phase, and the lattice parameter decreases almost linearly with the increasing Er concentration x. The dc magnetic susceptibility follows the Curie-Weiss law, and the Weiss temperature continuously changes from Theta = -24K for x = 0 to Theta = 15K for x = 1, indicating a change from antiferro-magnetism to ferromagnetism. Theta changes from negative to positive at around x = 0.2 where where a field-induced metamagnetic transition disappears. The magnetic ordering state continuously changes with the change in x from antiferromagnetic to ferromagnetic through a spin-glass-like behavior.

DOI： 10.7566/JPSJ.83.024701

Magnetic Phase Diagram of Ce1-xErxAl2 intermetallic compounds

Ohashi Masashi, Miyagawa Hidenori, Oomi Gendo, Nakano Tomohito, Satoh Isamu, Komatsubara Takemi

JPS Conference Proceedings 3 1183 - 1183 2014.1

Effect of Pressure and Ion Beam Irradiation on the Giant Magnetoresistance of Fe/Cr Magnetic Multilayers Reviewed

G. Oomi, T. Yayoi, T. Nakano, K. Saito, K. Takanashi, S. Mitani, A. Kohno, K. Sagara

IEEE TRANSACTIONS ON MAGNETICS 50 ( 1 ) 2014.1

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

The effect of high pressure and ion beam irradiation on the magnitude of giant magnetoresistance (GMR) of Fe/Cr magnetic multilayers (MML), [Fe(20 angstrom)/Cr(t angstrom)](20) (abbreviated as Fe/Cr(t)), has been measured at 77.4 K. It is found that the GMR of Fe/Cr(8) is decreased but that of Fe/Cr(30) is increased by applying pressure. By ion beam irradiation, the electrical resistance of these MMLs is increased significantly and the magnitude of GMR is decreased. Furthermore we have measured the GMR of irradiated Fe/Cr(8) and Fe/Cr(30) under high pressure and compared the results with the sample before irradiation. The GMR of Fe/Cr(8) after the irradiation is found to increase with pressure and the pressure-coefficient of the saturation resistivity is extremely large. These results are discussed on the basis of the spin dependent scattering by the roughness at the interfaces and also bulk scattering in MML in connection with an irradiation-induced instability of the electronic states in Fe/Cr(8).

DOI： 10.1109/TMAG.2013.2277875

Transport properties of a single crystal of pressure-induced superconductor CePtSi2 in the magnetic field Reviewed

Tomohito Nakano, Shintaro Onuki, Naoya Takeda

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 493 109 - 111 2013.10

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

We measured the electrical resistivity of the single crystal of pressure-induced superconductor CePtSi2, which was synthesized by the In-flux method, with the excitation current parallel to the tetragonal a-axis at various magnetic fields parallel to the c-axis. The Neel temperature T-N of 1.8 K at 0 T decreases with increasing magnetic field and disappears above B-c similar to 4.5 T. In the low-temperature region, the resistivity exhibits a Fermi-liquid-like T-2-dependence below T-FL similar to 1 K, which does not show a significant change up to B-c but increases above Bc. The resistivity drastically decreases by applying a magnetic field, and the magnetoresistance ratio attains to similar to 10, at 3.7 K. (C) 2013 Published by Elsevier B.V.

DOI： 10.1016/j.physc.2013.03.040

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

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 2013.8

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

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

Transport Properties of a Single Crystal of Pressure-Induced Superconductor CePtSi2 Reviewed

Tomohito Nakano, Shintaro Onuki, Naoya Takeda

JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 26 ( 6 ) 2135 - 2137 2013.6

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

We synthesized single crystals of pressure-induced superconductor CePtSi2 by an In-flux method, and measured its electrical resistivity rho under hydrostatic pressure. At ambient pressure, rho shows two maxima at T-1 = 3.7 K and T-2 = 33 K, and a downward bend at the Neel temperature T-N. With increasing pressure T-N decreases and disappears above 1.11 GPa, as reported in a polycrystalline sample. On the other hand, the maximum at T-1 becomes a shoulder above P-v = 1.21 GPa, and begins to increase with increasing pressure, indicating the beginning of a valence crossover.

DOI： 10.1007/s10948-012-1896-3

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