Faculty Profiles - NAKANO Tomohito

Papers - NAKANO Tomohito

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Coexistence of distinct Ce 4f-electron states at inequivalent crystallographic sites: CePtGe2 case

Hayato Muto, Tomohito Nakano, Tatsuya Watanabe, Ryota Takahashi, Naoya Takeda, Jun Gouchi, Yoshiya Uwatoko, Michal Dušek, Jan Prokleška, Jiří Pospíšil, Vladimír Sechovský

Journal of Magnetism and Magnetic Materials 613 172670 - 172670 2025.2

First-order transition under a magnetic ordered state in SmPtSi<sub>2</sub> Reviewed

Tomohito Nakano, Eisuke Takahashi, Shuto Yamaguchi, Naoya Takeda, Klára Uhlířová, Jan Prokleška, Jiří Pospíšil, Vladimír Sechovský, Kazuyuki Matusbayashi, Hanming Ma, Yoshiya Uwatoko

Physica Scripta 99 ( 8 ) 085923 - 085923 2024.7

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IOP Publishing

Abstract

We have synthesized polycrystalline and single-crystalline samples of SmPtSi<sub>2</sub>, and measured their resistivity, specific heat, magnetization, and Seebeck coefficient. The existence of two magnetic phase transitions has been confirmed, one at T <sub>H</sub> = 8.6 K and the other T <sub>L</sub> = 5.6 K. A hump-type anomaly in resistivity, a lambda-type anomaly in specific heat, a downward bend in magnetization, and a semiconductor-like increase in the Seebeck coefficient were observed at T <sub>H</sub>, indicating an antiferromagnetic transition accompanied by a gap opening on the Fermi surface. In contrast, a sharp drop in resistivity, a sharp spike in specific heat, and a drop in magnetization were observed at T <sub>L</sub>. The Seebeck coefficient showed metallic temperature dependence below T <sub>L</sub>. With increasing pressure, T <sub>H</sub> and T <sub>L</sub> shifted to higher temperatures. The transition at T <sub>L</sub> was no longer observed at pressures above 1.5 GPa. These findings suggest that the transition at T <sub>L</sub> is a transition from an antiferromagnetic ordered state with the gap on the Fermi surface to a different antiferromagnetic state.

DOI： 10.1088/1402-4896/ad59e0

Other Link： https://iopscience.iop.org/article/10.1088/1402-4896/ad59e0/pdf

Y-Substitution Effects on Electrical Resistivity of (Ce<sub>1−</sub><i><sub>y</sub></i>Y<i><sub>y</sub></i>)PtGe<sub>2</sub> Reviewed

Hayato Muto, Shoma Onuma, Tatsuya Watanabe, Ryota Takahashi, Tomohito Nakano, Naoya Takeda, Jun Gouchi, Yoshiya Uwatoko, Klára Uhlířová, Jan Prokleška, Vladimír Sechovský

Proceedings of the 29th International Conference on Low Temperature Physics (LT29) 38 011078-1 - 011078-5 2023.5

Transport and Thermal Properties of α-Mn under Pressure Reviewed

Tomohito Nakano, Kei Fukuhra, Arisa Tomaru, Hayato Muto, Naoya Takeda, Yusuke Amakai, Shigeyuki Murayama

Proceedings of the 29th International Conference on Low Temperature Physics (LT29) 38 011072-1 - 011072-6 2023.5

Magnetic separation of nickel-plating waste liquid using a high temperature superconducting bulk magnet

T Oka, K Sudo, J L Dadiel, N Sakai, H Seki, M Miryala, M Murakami, T Nakano, M Ooizumi, K Yokoyama, M Tsujimura

Superconductor Science and Technology 35 ( 9 ) 094006 - 094006 2022.9

Publishing type：Research paper (scientific journal) Publisher：IOP Publishing

Abstract

Ni is one of the important metal resources. Because Ni-containing waste liquid is drained after several plating turns in the factories, an effective recycling technique should be developed. A unique magnetic separation technique using high temperature superconducting bulk magnet has succeeded in collecting Ni-sulfate crystals, which were fabricated from the Ni-plating waste liquid. Pulsed-field magnetizing method was employed to activate the bulk magnet up to 2.80 T, which produced a field space of 1.40 T on the surface of the waste channel. Green coarse crystals were attracted from the flowing stream of Ni-saturated liquid containing weakly-magnetic particles of Ni-compounds. The magnetically-collected particles were identified as paramagnetic NiSO<sub>4</sub>/6H<sub>2</sub>O crystals, and slight differences in Ni concentration and grain size were observed between the particles attracted and not-attracted to the 1.8 T magnetic pole. In both cases, the large grains were found to consist of a single phase. The compound can be used as a raw material in the Ni-recycle process. This preferential extraction suggests a novel recycling method of Ni resource.

DOI： 10.1088/1361-6668/ac7f61

Other Link： https://iopscience.iop.org/article/10.1088/1361-6668/ac7f61/pdf

La-Substitution Effects on Multisite Ce Compound CePtGe<inf>2</inf>

Hayato Muto, Shoma Onuma, Tomohito Nakano, Naoya Takeda, Jun Gouchi, Yoshiya Uwatoko, Klára Uhlířová, Jan Prokleška, Vladimír Sechovský

Journal of the Physical Society of Japan 91 ( 7 ) 2022.7

Publishing type：Research paper (scientific journal)

The CePtGe2 compound, which shows antiferromagnetic transition at Néel temperature TN = 3.8 K, has two crystallographically inequivalent Ce sites. Recently, the coexistence of a localized f-electron state at one of two Ce sites and an itinerant heavy f-electron state at the other Ce site has been suggested. In this study, we have prepared polycrystalline samples of (Ce1-xLax)PtGe2 (x = 0 ∼ 0.2) and have measured their electrical resistivity and magnetization. The specific heat for x = 0.2 has been measured also. With increasing x, the downward bending of the temperature dependence of the resistivity and the cusp-type anomaly in the susceptibility associated with TN shift to lower temperatures with a linear extrapolation of TN directing to 0 K at x ∼ 0.5. Also, the saturation magnetization decreases linearly with increasing x, pointing to the disappearance of magnetic moments at the same La concentration. These results indicate that only the Ce ions with the localized f-electron are substituted by La ions. On the other hand, the transition from the antiferromagnetic state to the ferromagnetic-like polarized magnetic state at a very weak magnetic field, which is comparable to that of conventional Ferrite magnets, was realized via the La-substitution.

DOI： 10.7566/JPSJ.91.074712

Pressure dependence of the magnetic ground state in CePtSi2

S. E. Dissanayake, F. Ye, W. Tian, M. Matsuda, H. Muto, S. Suzuki, T. Nakano, S. Watanabe, J. Gouchi, Y. Uwatoko

Physical Review B 105 ( 24 ) 2022.6

Publishing type：Research paper (scientific journal)

CePtSi2 was reported to exhibit an antiferromagnetic order below T∗=1.8 K at ambient pressure, a valence state change at ∼1.2 GPa, and superconductivity in the range between 1.4 and 2.1 GPa with a maximum transition temperature of 0.14 K [T. Nakano, Phys. Rev. B 79, 172507 (2009)1098-012110.1103/PhysRevB.79.172507]. We have performed polycrystalline and single-crystal neutron diffraction experiments to determine the magnetic structure under ambient and high pressures. We found incommensurate magnetic peaks with a magnetic propagation vector of (0.32,0,0.11) at ambient pressure below TSDW∼1.25 K. Those magnetic peaks originate from a spin-density-wave order with the easy axis along the c axis and an averaged ordered moment of 0.45(5)μB, suggesting that there may be an intermediate phase between T∗ and TSDW. Applying pressures, the magnetic propagation vector shows no change and the magnetic order disappears around 1.0 GPa, which is much lower than the critical pressure for the superconducting phase. The results suggest that other than magnetic fluctuations may play a primary role in the superconducting pairing mechanism.

DOI： 10.1103/PhysRevB.105.245111

High-Pressure Thermopower of the Mott Insulator Ca<inf>2</inf>RuO<inf>4</inf>

Isuzu Sano, Tomohito Nakano, Akitoshi Nakano, Hiroki Taniguchi, Fumihiko Nakamura, Ichiro Terasaki

Journal of the Physical Society of Japan 91 ( 3 ) 2022.3

Publishing type：Research paper (scientific journal)

We have measured and analyzed the thermopower of single-crystal samples of the Mott insulator Ca2RuO4 in high pressure up to 0.9 GPa. We find that the thermopower rapidly changes at a metal-insulator transition temperature, which is explained in terms of a percolation theory. In contrast, the thermopower in the insulator phase slightly decreases with increasing pressure well below the transition temperature, and is associated with thermodynamic quantities through the Kelvin formula. The pressure dependence is compared with the current-density dependence, and a possible origin for the current-enhanced thermopower is proposed.

DOI： 10.7566/JPSJ.91.033703

Feasible waste liquid treatment from electroless nickel-plating by intense magnetic field of HTS bulk magnets

T. Oka, M. Furusawa, K. Sudo, L. Dadiel, N. Sakai, H. Seki, M. Miryala, M. Murakami, T. Nakano, M. Ooizumi, K. Yokoyama, M. Tsujimura

Progress in Superconductivity and Cryogenics (PSAC) 23 ( 3 ) 37 - 40 2021

Publishing type：Research paper (scientific journal)

Nickel (Ni) is a kind of the rare earth resources. Since Ni-containing waste is drained after several plating operations in the factories, the effective recycling technique has been expected to be introduced. An actual magnetic separation technique using HTS bulk magnet generating the strong magnetic field has succeeded in collecting the paramagnetic slurry containing Ni-sulphate coarse crystals which were fabricated from the Ni-plating waste. The Ni compound in the collected slurry was identified as NiSO4/6H2O, showing slight differences in the particle size and magnetic susceptibility between the samples attracted and not-attract to the magnetic pole. This preferential extraction suggests us a novel recycling method of Ni resource because the compound is capable of recycling back to the plating processes as a raw material.

DOI： 10.9714/psac.2021.23.3.037

Novel magnetizing technique using high temperature superconducting bulk magnets for permanent magnets in interior permanent magnet rotors

T. Oka, S. Hasebe, J. Ogawa, S. Fukui, T. Nakano, N. Sakai, M. Miryala, M. Murakami, K. Yokoyama

Superconductor Science and Technology 33 ( 8 ) 2020.8

Publishing type：Research paper (scientific journal)

A novel magnetizing technique for permanent magnets (PMs) embedded in interior permanent magnet (IPM) motors has been proposed as a safer and more effective process than the conventional processes using copper pulse-coils. In the new process, the high temperature superconducting (HTS) bulk magnet, emitting an intense magnetic field of over 3 T, was employed to activate the rotor and PMs inside. A magnetic pole containing the HTS bulk magnet was scanned on the surface of the IPM rotor, resisting against the extremely strong attractive force between the magnet and rotor. Following experiments in the past, numerical simulation studies have been conducted to evaluate the magnetic field-trapping performances of the PMs. In this study, the numerical analysis of the magnetization behaviours was conducted for the PMs embedded in the rotor of the commercial air-conditioner motor in a hybrid car. The simulation results showed us that the demagnetized Nd-Fe-B plates in the rotor were fully magnetized in the intense static magnetic fields on the magnetic pole containing the HTS bulk magnet. The magnetizing behaviour in this peculiar magnetizing operation was made understandable by estimating the anisotropic easy-direction of the PM plates embedded in the rotor. The novel activation method for PM is characterized as a no-shock and no-heating method, which would promote the degree of freedom in the IPM motor design.

DOI： 10.1088/1361-6668/ab9543

Superconductivity of the ternary stannide Y<inf>5</inf>Co<inf>6</inf>Sn<inf>18</inf>

Naoki Kase, Taishi Anada, Yusuke Terui, Tomohito Nakano, Naoya Takeda

Physica B: Condensed Matter 587 2020.6

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

Superconductivity is newly discovered in a single crystal of Y5Co6Sn18 at superconducting transition temperature T-c = 0.7 K. The single crystals are grown by a Sn flux method. Superconducting and normal properties of Y5Co6Sn18 are investigated by means of electrical resistivity rho(T) and specific heat C(T) measurements. Superconductivity is of bulk nature because of the jump at T-c from specific heat measurements. The Sommerfeld constant gamma and Debye temperature Theta(D) are estimated to be 9.6 mJ/(mol .K-2) and 450 K. The upper critical filed mu H-0(c2)(0) is estimated to be 0.825 T obtained from rho(T) in several magnetic fields.

DOI： 10.1016/j.physb.2020.412149

Magnetizing Technique for Permanent Magnets in IPM Motor Rotors Using HTS Bulk Magnet

T. Oka, S. Hasebe, J. Ogawa, S. Fukui, T. Nakano, K. Yokoyama, M. Miryala, N. Sakai, M. Murakami

IEEE Transactions on Applied Superconductivity 30 ( 4 ) 2020.6

Publishing type：Research paper (scientific journal)

A unique activation technique for permanent Nd-Fe-B magnets which were embedded in the rotors of interior permanent magnet (IPM) motors has been developed as a magnetizing tool with use of high temperature superconducting (HTS) bulk magnet. The experimental and numerical simulation studies were conducted to evaluate the magnetic field-trapping performances of the rotor of air-conditioner compressor in the hybrid-type automobiles. The sample rotor containing six demagnetized permanent magnet plates were exposed in the intense static magnetic fields above the magnetic pole which contained the bulk magnet generating over 4 T. As a result, the sample magnets were perfectly magnetized in the static magnetic field. The precise simulation on the flux distribution in the rotor clarified that it is important to make the flux direction in the rotor core and the easy magnetization axis of PM identical. We convinced this activation technique should enable us to promote the degrees of freedom of motor designing and its processing.

DOI： 10.1109/TASC.2020.2989181

Coexistence of localized and heavy itinerant states in antiferromagnetic CePtG e2 Reviewed

Tomohito Nakano, Shoma Onuma, Naoya Takeda, Klára Uhlířová, Jan Prokleška, Vladimír Sechovský, Jun Gouchi, Yoshiya Uwatoko

Physical Review B 100 ( 3 ) 2019.7

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

Two conflicting ground states, i.e., an antiferromagnetic ground state at 3.8K and aferromagnetic ground state at 5.1 K, have been reported for CePtGe2, which has two nonequivalent crystallographic Ce sites. In this study, we have prepared polycrystalline and single-crystalline CePtGe2 samples and measured their magnetization, specific heat, resistivity, and Seebeck coefficient. The observed bend in resistivity, peak in magnetic susceptibility, and lambda-type anomaly in specific heat at T-N = 3.8K and the metamagnetic transition in this CePtGe2 suggest antiferromagnetism at low temperatures. No evidence of ferromagnetic order was found in the studied temperature range, indicating possible crystal polymorphism with ferromagnetic character. The large susceptibility around TN and the Schottky-type specific heat indicate a well-localized f -electron state. However, the large residual gamma and X(0) indicate an itinerant heavy f -electron state. These findings suggest the coexistence of localized and heavy itinerant states corresponding to f electrons at the two Ce sites in this antiferromagnetic CePtGe2. The field dependence of magnetization indicates a sudden increase in magnetization at weak magnetic fields (similar to 0.2T), followed by a plateau at fields above 0.2 T, resulting in a possible different polarized metamagnetic state via interaction between localized and itinerant f electrons.

DOI： 10.1103/PhysRevB.100.035107

Pressure-Induced Superconductivity in CePtSi<sub>2</sub> Invited Reviewed International coauthorship

中野智仁

高圧力の科学と技術 29 ( 4 ) 283 - 289 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of High Pressure Science and Technology

<p>In this article, I introduce the pressure-induced superconductivity in CePtSi<sub>2</sub> with its discovering process. At ambient pressure, the orthorhombic CePtSi<sub>2</sub> shows an antiferromagnetic order below <i>T</i><sub>N</sub>=1.8 K. <i>T</i><sub>N</sub> disappears above 1.2 GPa, and a superconducting phase appears with <i>T</i><sub>c</sub>～0.1 K. Significant decrease of the <i>A</i> coefficient in resistivity and discrepancy between quantum critical point (QCP) and the center of the superconducting phase suggest the valence mediated superconductivity as that observed in CeCu<sub>2</sub> (Si,Ge)<sub>2</sub>.</p>

DOI： 10.4131/jshpreview.29.283

Collecting Ni-Sulfate Compound from Electroless Plating Waste by Magnetic Separation Technique with Use of HTS Bulk Magnets

T. Oka, S. Sasaki, H. Sasaki, S. Fukui, J. Ogawa, T. Sato, T. Nakano, M. Ooizumi, M. Tsujimura, K. Yokoyama

Journal of Physics: Conference Series 1054 ( 1 ) 2018.7

Publishing type：Research paper (international conference proceedings)

© Published under licence by IOP Publishing Ltd. The authors have developed a useful technique for extracting the Ni-sulfate compound from the "processed waste/fluid" of the electroless Ni-plating processes. After forming the fine NiHPO3 precipitate from the waste, the coarse NiSO4 crystals were synthesized through the reaction with the concentrated sulfuric acid. In the experiment, the open-gradient magnetic separation was employed to collect the NiSO4 crystals from the muddy mixture composed of these compounds. The experiments were practically conducted with use of the Gd123-based HTS bulk magnets generating up to 3.99 T, which were activated by the field cooling magnetizing method operated at 35 K. Intense magnetic field emitted from the bulk magnet attracted the paramagnetic fluid and coarse NiSO4 crystals on the bottom of the water channel, forming a giant drop of NiSO4-saturated clear fluid and the slurry of nickel sulfate hexahydrate. This preferential collection suggests a feasible recycling process of Ni resource as a raw material in the plating processes.

DOI： 10.1088/1742-6596/1054/1/012047

Fundamental properties of a new samarium compound SmPtSi<inf>2</inf> Reviewed

Shuto Yamaguchi, Eisuke Takahashi, Naoki Kase, Tomohito Nakano, Naoya Takeda, Kazuyuki Matsubayashi, Yoshiya Uwatoko

Physica B: Condensed Matter 536 297 - 299 2018.5

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

We have discovered a new orthorhombic ternary compound SmPtSi2. We succeeded in growing a single crystal of SmPtSi2; prepared a polycrystalline sample of this compound, and measured their susceptibility, specific heat, and resistivity. The temperature dependence of susceptibility of the polycrystalline sample is close to that of Sm3+ at high temperatures, and its specific heat shows anomalies at T-H = 8.6 K and T-L = 5.6 K. The resistivity of a single crystal of SmPtSi2 shows a hump-type anomaly just below T-H and a sudden decrease at T-L, indicating that these anomalies are intrinsic and that SmPtSi2 exhibits a two-step transition.

DOI： 10.1016/j.physb.2017.10.028

A review article: Compact magnetic field generators containing HTS bulk magnets cooled by refrigerators and their feasible applications

Tetsuo Oka, Jun Ogawa, Satoshi Fukui, Takao Sato, Tomohito Nakano, Kazuya Yokoyama, Takashi Nakamura, Hiroyuki Fujishiro, Koshichi Noto

High-Temperature Superconductors: Occurrence, Synthesis and Applications 291 - 306 2018.1

Publishing type：Part of collection (book)

Various types of strong magnetic field generators with use of HTS bulk magnets and the small-scale refrigerators have been actually proposed and experimentally estimated for the feasible applications. The most characteristic feature of bulk magnets is regarded as compact and strong field generators with respect to their magnetic field spaces or their machine structures of themselves. Among them, the magnetic flux density of the face-toface magnetic poles reached 3.2 T and 4.4 T when they were activated by the pulsed field magnetization and the field cooling method, respectively. Furthermore, a very small bulk magnet generating 2.8 T and the system featured by the wide magnetic poles containing seven magnets have been constructed with use of ST pulse tube coolers in order to expand the feasible application areas. On the other hand, although the bulk magnets are characterized by their steep field distributions, we attempted to gain the uniform magnetic field space, and successfully achieved the uniformity of 385 ppm in 4 mm range by combining the deformed magnetic field profiles which generated between the face-to-face magnetic poles. The performances of these unique systems have exceeded those of the conventional electromagnet or any permanent magnets by far, demonstrating the superiority to other strong magnetic field generators.

Superconducting gap symmetry of the BiS2-based superconductor LaO0.5F0.5BiSSe elucidated through specific heat measurements Reviewed

Naoki Kase, Yusuke Terui, Tomohito Nakano, Naoya Takeda

PHYSICAL REVIEW B 96 ( 21 ) 2017.12

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

In this study, the superconducting gap symmetry of LaO0.5F0.5BiSSe is elucidated through specific heat measurements with one single crystal of LaO0.5F0.5BiSSe. A clear jump is observed at 3.95 K in LaO0.5F0.5BiSSe, suggesting bulk superconductivity. From specific heat measurements, Delta C-e/gamma T-c and 2 Delta(0)/k(B)T(c) are obtained as 2.31 and 4.5. These values indicate strong electron-phonon coupling superconductivity. The temperature (T) and magnetic-field (H) dependence of the electronic specific heat C-e(T, H) suggests that superconductivity is fully gapped. Our handmade system successfully elucidates superconducting gap symmetry of the BiS2-based compound with a small single crystal.

DOI： 10.1103/PhysRevB.96.214506

Upper critical field of the single crystal La(O,F)BiSe2 Reviewed

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

Journal of Physics: Conference Series 871 ( 1 ) 5 pages - 12005 2017.7

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

Single crystal growth and superconducting properties of LaO0.5F0.5BiSe2 are studied. Single crystals of LaO0.5F0.5BiSe2 were grown by a CsCl-flux method. Electrical resistivity ρ(T) measurements were performed to elucidate its superconducting properties. The ρ(T) shows metallic behavior and superconducting transition at 4.0 K. From ρ(T) measurements in several magnetic fields, upper critical fields Hc2∥ab(0) and Hc2∥c (0) are estimated to be 7.05 T and 0.52 T, respectively. The superconducting anisotropic parameter Γ is determined to be 13.6.

DOI： 10.1088/1742-6596/871/1/012005

Superconducting gap of the single crystal β-PdBi2 Reviewed

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

Journal of Physics: Conference Series 871 ( 1 ) - 12004 2017.7

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

We investigate superconducting and normal properties of the single crystal of β-PdBi2. The electrical resistivity ρ(T) shows superconductivity at Tc = 5.0 K. Residual resistivity ratio (RRR) is estimated to be 2.9 obtained from ρ(300 K)/ρ(5.0 K). The Hc2 curve obtained from ρ(T) in magnetic fields shows cleat enhancement from the Wertharmer-Helfand-Hohenberg theory in dirty limit. Specific heat C(T) measurement shows that clear jump is observed at Tc = 4.8 K. T-dependence of the electronic specific heat Ce(T) suggests full-gap symmetry with a single gap and strong coupling with ΔCe/γTc = 1.8.

DOI： 10.1088/1742-6596/871/1/012004

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

Magnetic phase diagram of clathrate compound Ce3Pd 20Si6 with quadrupolar ordering Reviewed

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

Journal of Physics Condensed Matter 25 ( 12 ) 126003(1-4) 2013.3

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

We present results of specific heat measurements on a Ce3Pd 20Si6 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 V [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. © 2013 IOP Publishing Ltd.

DOI： 10.1088/0953-8984/25/12/126003

Magnetization, Resistivity and Specific Heat of Hexagonal R2Ni12P7 with Filled-Cr12P7 Structure Reviewed

Tomohito Nakano, Katsuhiko Tsuchiya, Atsumi Ohashi, Takashi Nashimoto, Hiroki Ono, Naoya Takeda, Naoki Shirakawa

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 ( 7 ) 074601-1-8 - 1 2012.7

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

We prepared single-crystal samples of hexagonal R2Ni12P7 (R = Sm, Gd-Lu) using a Sn-flux method, and measured their magnetization, resistivity, and specific heat. The antiferromagnetic order in Gd2Ni12P7 and Ho2Ni12P7, the ferromagnetic order in Dy2Ni12P7 and Er2Ni12P7, and the ferromagnetic-like order in Sm2Ni12P7, Tb2Ni12P7, and Tm2Ni12P7 were evidenced by the results of the measurements. In contrast, we found that Yb2Ni12P7 is in a heavy fermion state at low-temperature region. Hump-type anomalies in specific heat were observed below the magnetic transition temperature in R2Ni12P7 (R = Gd, Tb, and Dy), indicating the Zeeman splitting of the J-multiplet of the R3+ ion in the ordered state.

DOI： 10.1143/JPSJ.81.074601

Magnetic properties of cubic compound Ce6Ni6P17 with geometric frustrations Reviewed

N. Takeda, K. Izumi, H. Ono, S. Yodono, T. Nakano

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 2012

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

We report the magnetic susceptibility and the low-temperature specific heat of Ce6Ni6P17 with geometric frustrations and La6Ni6P17 as a nonmagnetic counterpart. The magnetic susceptibility of Ce6Ni6P17 decreases monotonically with decreasing temperature and the specific heat shows a broad peak around 1.4 K. The evaluated magnetic entropy is about a half of Rln2 at 5.0 K. This result suggests that the frustrations persist down to very low temperatures and the residual entropy originate from frustration is present.

DOI： 10.1088/1742-6596/391/1/012071

Pressure-induced magnetic instability in Pd-Ni alloys Reviewed

Gendo Oomi, Sadanori Iwai, Masashi Ohashi, Tomohito Nakano

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 ( 1 ) 12103 2012

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

The electrical resistivity rho(T) of dilute Pd-Ni alloys has been measured at high pressure up to 3 GPa. It is found that the rho(T) of the ferromagnetic Pd-Ni alloy shows an anomalous temperature dependence near the critical pressure P-c, where the ferromagnetism disappears. The results are analysed in the framework of quantum critical behaviour induced by pressure. The effect of magnetic field on the rho(T) is also examined. Different behaviour of magnetoresistance against pressure was found depending on the alloy concentration and discussed in connection with an instability of ferromagnetism.

DOI： 10.1088/1742-6596/391/1/012103

Pressure effect of transport properties of hexagonal Yb2Ni12P7 Reviewed

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

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 ( 1 ) 12052 2012

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

Magnetic properties of Ce1-xLaxRu2Si 2 compounds Reviewed

D. Abe, Y. Amakai, S. Murayama, N. Momono, H. Takano, T. Nakano, K. Matsubayashi, Y. Uwatoko

Journal of Physics: Conference Series 391 ( 1 ) 12001 2012

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

We have measured the susceptibility χ and resistivity ρ on single-crystalline Ce1-xLaxRu2Si2 for 0 ≤ x ≤ 0.8 in directions parallel (//) and perpendicular (⊥) to the c-axis. The χ// for 0.1 ≤ x ≤ 0.7 indicates a Curie-Weiss form at T &gt
20 K and a typical AF maximum at TN. A significant crossover between TN and the magnitude of the Weiss temperature |Θ| occurs at about x = 0.2. The ρ⊥ shows a gap-type upturn at TN for 0.1 ≤ x ≤ 0.185 with rather a downward bend ρ// at around TN. The upturn in ρ⊥ at TN disappears for x = 0.2 with a sharp maximum ρ// at TN. A sharp peak in ρ⊥ takes place at TN for 0.3 ≤ x ≤ 0.7 with the sharp maximum ρ// at TN for 0.4 ≤ x ≤ 0.6. These results can be interpreted as the evolution from the itinerant SDW in the heavy-fermion band for 0.1 ≤ x &lt
0.2 to the AF ordering with the local moment for x &gt
0.2 up to x = 0.7. © Published under licence by IOP Publishing Ltd.

DOI： 10.1088/1742-6596/391/1/012001

Specific heat of Ce3Pd20Si6 single crystal in magnetic fields Reviewed

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

Journal of Physics: Conference Series 391 ( 1 ) 12054 2012

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

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'. © Published under licence by IOP Publishing Ltd.

DOI： 10.1088/1742-6596/391/1/012054

Specific heat of Ce3Pd20Si6 single crystal in magnetic fields Reviewed

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 2012

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

Magnetic properties of cubic compound Ce6Ni6P 17 with geometric frustrations Reviewed

N. Takeda, K. Izumi, H. Ono, S. Yodono, T. Nakano

Journal of Physics: Conference Series 391 ( 1 ) 12071 2012

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

We report the magnetic susceptibility and the low-temperature specific heat of Ce6Ni6P17 with geometric frustrations and La6Ni6P17 as a nonmagnetic counterpart. The magnetic susceptibility of Ce6Ni6P17 decreases monotonically with decreasing temperature and the specific heat shows a broad peak around 1.4K. The evaluated magnetic entropy is about a half of Rln2 at 5.0 K. This result suggests that the frustrations persist down to very low temperatures and the residual entropy originate from frustration is present. © Published under licence by IOP Publishing Ltd.

DOI： 10.1088/1742-6596/391/1/012071

Thermal and electronic properties of rare earth compounds at high pressure

Uwatoko, Y., Umehara, I., Ohashi, M., Nakano, T., Oomi, G.

Handbook on the Physics and Chemistry of Rare Earths 42 ( 1 ) 2012

Physical Properties of Unfilled Skutterudite NiP3 Reviewed

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 SA035-1-2 2011.7

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

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.K-2.

DOI： 10.1143/JPSJS.80SA.SA035

Low-Temperature Magnetic Properties of Ho2Ni12P7 Reviewed

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 SA081-1-2 2011.7

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

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 Neel temperature T-N = 10 K. The magnetization exhibits a metamagnetic behavior below T-N. The specific-heat shows a clear peak due to the transition. The crystalline-field ground state of Ho2Ni12P7 is a doublet.

DOI： 10.1143/JPSJS.80SA.SA081

The magnetic moment without magnetic phase transition in insulating RR'S-3(R=La, Ce, Pr, Nd; R'=Yb, Lu) Reviewed

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 2011.7

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

We have synthesized RR'S-3(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 chi(-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.

DOI： 10.1143/JPSJS.80SA.SA079

Seebeck coefficient of concentrated Kondo compound CePtSi2 under hydrostatic pressure Reviewed

Tomohito Nakano, Shouta Yonamine, Masato Hedo, Takao Nakama, Masashi Ohashi, Naoya Takeda, Gendo Oomi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 SA058-1-2 2011.7

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

We measured the Seebeck coefficient and resistivity of the concentrated Kondo compound CePtSi2 under hydrostatic pressure. At ambient pressure, S gradually increases with decreasing temperature and shows a maximum value S-max = 28 mu V/K around 86 K, followed by a minimum around 4.5 K, as is often observed in antiferromagnetic Ce-based heavy fermion compounds. With increasing pressure, S at high temperature increases, whereas S below 20 K does not show a significant change.

DOI： 10.1143/JPSJS.80SA.SA058

Pressure-induced half-metallic gap transformation in Co2MnSi observed by tunneling conductance spectroscopy Reviewed

M. Nobori, T. Nakano, J. Hasegawa, G. Oomi, Y. Sakuraba, K. Takanashi, Y. Miura, Y. Ohdaira, Y. Ando

PHYSICAL REVIEW B 83 ( 10 ) 104410-1-6 2011.3

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

Applied hydrostatic pressure dependence of tunneling magnetoresistance (TMR) properties was investigated in magnetic tunnel junctions using the half-metallic Heusler alloy Co2MnSi (CMS). The half-metallic electronic structure in CMS was observed by measuring tunneling-conductance spectroscopy under different applied pressure. The effect of tetragonal distortion in CMS on the electronic structure was also calculated on the basis of the first-principle density-functional method. The TMR ratio showed no remarkable variation with increasing pressure from ambient to 1.5 GPa. It was clearly found that the valence-band edge of the half-metallic gap moved toward the Fermi level with increasing pressure up to 1.8 GPa. These experimental results showed good qualitative agreement with the theoretical calculation of density of states of CMS at high pressure.

DOI： 10.1103/PhysRevB.83.104410

Uniaxial colossal magnetoresistance in the Ising magnet SrCo12O19 Reviewed

S. Ishiwata, T. Nakano, I. Terasaki, H. Nakao, Y. Murakami, Y. Uwatoko, M. Takano

PHYSICAL REVIEW B 83 ( 2 ) 020401-1-4 2011.1

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

A new type of colossal magnetoresistance, which is extremely sensitive to the magnetic-field direction, was discovered in a magnetoplumbite-type hexagonal cobalt oxide SrCo12O19 synthesized under a high pressure of 3 GPa. SrCo12O19 has a unique combination of physical properties (i.e., uniaxial magnetic anisotropy originating from Ising spins on Co3+O5 bipyramids and a metal-insulator transition taking place on a three-dimensional network of Co3+/4+O6 octahedra). The resistivity decreases by a factor of 1000 when a magnetic field of 10 T is applied along the hexagonal axis (magnetic easy axis) in the insulating phase, whereas it is rather robust against the field perpendicular to this axis. These results demonstrate a metal-insulator crossover dominated by the orientation order of built-in Co3+ Ising spins embedded in the conductive Co3+/4+-O matrix lattice.

DOI： 10.1103/PhysRevB.83.020401

Thermal and electrical conduction properties of vertically aligned carbon nanotubes produced by water-assisted chemical vapor deposition Reviewed

Atsuto Okamoto, Itaru Gurjishima, Takashi Inoue, Megumi Akoshima, Hidenori Miyagawa, Tomohito Nakano, Tetsuya Baba, Masaki Tanemura, Gendo Oomi

CARBON 49 ( 1 ) 294 - 298 2011.1

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

We present both thermal and electrical conduction properties of vertically aligned carbon nanotubes (VACNTs), synthesized by the water-assisted chemical vapor deposition method using Fe-Ti-O nanoparticles as catalyst Thermal diffusivity and electrical resistance of VACNTs have been measured by the laser flash method and direct current four-terminal method, respectively The VACNTs are found to have thermal diffusivities of the same order as isotropic graphite and the electrical characteristics of semiconductors The electrical resistance shows a T(-1/4) temperature dependence, which implies that the conduction of electrons is dominated by 3D Mott variable range hopping (C) 2010 Elsevier Ltd All rights reserved

DOI： 10.1016/j.carbon.2010.09.024

Effect of Pressure on Transport Properties of Heavy Fermion CePtSi2 Reviewed

Tomohito Nakano, Masashi Ohashi, Gendo Oomi, Kazuyuki Matsubayashi, Yoshiya Uwatoko

JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 23 ( 5 ) 799 - 801 2010.7

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

We measured the resistivity of heavy fermion CePtSi2 under pressure. At ambient pressure, CePtSi2 shows an antiferromagnetic (AF) transition at 2 K and a Fermi liquid like T-2 dependence ill resistivity below 1.5 K. With increasing pressure, the AF phase and T-2 dependence are suppressed. Above 1.4 GPa, a T linear dependence and pressure-induced superconductivity were found with the maximum T-c = 0.14 K at 1.7 GPa. Above 2 GPa, the T-2 dependence recovers just above T-c.

DOI： 10.1007/s10948-010-0743-7

Transport properties of the layered Rh oxide K0.49RhO2 Reviewed

S. Shibasaki, T. Nakano, I. Terasaki, K. Yubuta, T. Kajitani

JOURNAL OF PHYSICS-CONDENSED MATTER 22 ( 11 ) 115603-1-5 2010.3

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

We report measurements and analyses of resistivity, thermopower and the Hall coefficient of single-crystalline samples of the layered Rh oxide K0.49RhO2. The resistivity is proportional to the square of the temperature up to 300 K, and the thermopower is proportional to the temperature up to 140 K. The Hall coefficient increases linearly with the temperature above 100 K, which is ascribed to the triangular network of Rh in this compound. The different transport properties between NaxCoO2 and K0.49RhO2 are discussed on the basis of the different bandwidth between Co and Rh evaluated from the magnetotransport.

DOI： 10.1088/0953-8984/22/11/115603

Effect of pressure on the superconductivity and magnetism in HoNi2B2C Reviewed

Masatoshi Nobori, Tomohito Nakano, Gendo Oomi, P. C. Canfield, B. K. Cho

INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 ( 1 ) 012146-1-4 2010

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

The electrical resistivity of single crystalline HoNi2B2C has been measured under pressure up to 3.0 GPa. At ambient pressure, the resistivity shows sudden drop below T-c = 8.8 K, and becomes zero below 8.0 K. At 2.0 GPa, it drops below T-c = 8.1 K, becomes zero below 7.2 K, and shows a peak around 5.9 K due to the antiferromagnetic (AFM) order. Then it becomes zero again below 5.7 K. It is observed that the superconductivity is affected strongly by changing current density. T-c with 5.6 A/cm(2) decreases with increasing pressure. On the other hand, T-c increases when a current density is close to the critical current density J(c) = 63.9 A/cm(2) with increasing pressure up to 3.0 GPa.

DOI： 10.1088/1742-6596/200/1/012146

Novel thermoelectric properties of complex transition-metal oxides Reviewed

Ichiro Terasaki, Manabu Iwakawa, Tomohito Nakano, Akira Tsukuda, Wataru Kobayashi

DALTON TRANSACTIONS 39 ( 4 ) 1005 - 1011 2010

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

We report how the thermopower of complex transition-metal oxides is susceptible to small changes in material parameters. In the A-site ordered perovskite oxide R(2/3)Cu(3)Ti(3.6)Ru(0.4)O(12), the thermopower changes from 15 to -100 mu VK(-1) at 300 K in going from R = La to Er. We associate this with the hybridization between Cu 3d and Ru 4d electrons, which depends on R. For stronger hybridization, the Cu 3d electrons become more itinerant leading to positive thermopower. In the A-site ordered perovskite cobalt oxide Sr(3)YCo(4)O(10.5), the spin state of the Co(3+) ions determines the magnitude of the thermopower, where partial isovalent substitution (Ca for Sr and Rh for Co) enhances the thermopower whilst keeping the resistivity intact. These substitutions stabilize the low spin state of the Co(3+) ions, which affects the thermopower through the entropy of the background for the carriers. We propose that the control of the magnetism plays a pivotal role in determining the thermopower in a certain class of complex oxides.

DOI： 10.1039/b914661j

Pressure effect on magnetic properties of a weak ferromagnet BaIrO3 Reviewed

Takanori Kida, Atsuko Senda, Shunsuke Yoshii, Masayuki Hagiwara, Tomohito Nakano, Ichiro Terasaki

INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 2010

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

We have investigated the pressure effect on magnetic properties of a weak itinerant ferromagnet BaIrO3, using a Cu-Be piston-cylinder type pressure cell. Under external pressure the ferromagnetic transition temperature T-c decreases linearly with pressure at a large rate of dT(c)/dP similar to -17 K/GPa. The critical exponent beta up to 0.86 GPa indicates the anomalous value (beta similar to 0.9) and is nearly pressure-independent. Anomalous pressure effects on conductivity and magnetism suggest the existence of a nontrivial coupling among charge, spin and lattice in this compound.

DOI： 10.1088/1742-6596/200/1/012084

Pressure-induced Quantum Phase Transition in Cr1-xVx Alloys

Oomi G., Fuchizaki Y., Ohashi M., Nakano T., Uwatoko Y.

Transactions of the Magnetics Society of Japan 34 ( 3 ) 263 - 266 2010

Language：English Publisher：The Magnetics Society of Japan

The electrical resistivities and Hall effect of Cr<sub>1-x</sub>V<sub>x</sub> alloys(x<0.04) were measured at high pressure. The Néel temperature T<sub>N</sub> of x = 0.015, 0.032 and 0.035 was found to disappear at corresponding P<sub>c</sub> of 5.6 GPa, 1.1 GPa and 0.7 GPa, respectively. The Hall coefficients of x = 0.032 and 0.035 demonstrated a discontinuous change around P<sub>c</sub>, which implies a quantum phase transition induced by high pressure. We found that the exponents in the power law of resistivity of x = 0.015 had an anomaly around P<sub>c</sub>, which means that the large quantum fluctuations affect the resistivity even at high temperature. A possibility of superconductivity is explored near P<sub>c</sub> for x = 0.032. A slight decrease in the ρ(T) curve was observed below 1 K at high pressure. The origins for that are briefly discussed.

DOI： 10.3379/msjmag.1003R045

Other Link： https://jlc.jst.go.jp/DN/JALC/00351380509?from=CiNii

Chemical and Physical Pressure Effects on the Magnetic and Transport Properties of the A-Site Ordered Perovskite Sr3YCo4O10.5 Reviewed

Shin Yoshida, Wataru Kobayashi, Tomohito Nakano, Ichiro Terasaki, Kazuyuki Matsubayashi, Yoshiya Uwatoko, Inga Grigoraviciute, Maarit Karppinen, Hisao Yamauchi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 9 ) 094711-1-5 - 94711 2009.9

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

We have measured and analysed the magnetization, resistivity and thermopower of polycrystalline samples of Ca-subsituted Sr3YCo4O10.5. While the transition temperature and thermopower systematically decrease with increasing Ca content, the resistivity is nearly independent of the Ca-substitution level. We have furhter found that the substitution of Ca for Sr systematically decreases the lattice paremeters while maintaining the oxygen content unchanged, and have explained the Ca-substitution effects in terms of the spin-state transition induced by chemical pressure. We have also measured the magnetization of one of the samples under hydrostatic pressure. The result shows that the physical-pressure effect is semiquantitatively consistent with the chemical-pressure effect.

DOI： 10.1143/JPSJ.78.094711

Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2-xFexCrSi Reviewed

Masahiko Hiroi, Tsugumi Rokkaku, Kazuhisa Matsuda, Toru Hisamatsu, Iduru Shigeta, Masakazu Ito, Takuo Sakon, Keiichi Koyama, Kazuo Watanabe, Shintaro Nakamura, Tsutomu Nojima, Tomohito Nakano, Lin Chen, Tetsuya Fujiwara, Yoshiya Uwatoko, Hirotaka Manaka, Norio Terada

PHYSICAL REVIEW B 79 ( 22 ) 224423-1-10 2009.6

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

The results of a comprehensive study of the structural, magnetic, and magnetotransport properties of the Heusler compounds Ru2-xFexCrSi are presented. The Fe-rich compounds (x >= 1.5) exhibit a usual ferromagnetic transition. The Ru-rich compound (x=0.1) does not show ferromagnetism but exhibits a peak in magnetic susceptibility at T-N(*)=30 K. Nevertheless, specific-heat measurements show that there is no antiferromagnetic transition at T-N(*) nor at any other temperatures. With further decreasing temperature strong irreversible behavior occurs below a temperature T-g. It is proposed that these results can be interpreted as successive spin-glass transitions at T-N(*) and T-g. The compounds with intermediate x (=0.3 and 0.5) are found to be ferromagnetic. Both the saturation magnetization and the Curie temperature T-C increase with increasing x. However, being different from the Fe-rich compounds, hysteresis of the magnetization is observed and this suggests that the ferromagnetism has glassy character. In lower-temperature range fairly large negative magnetoresistance are observed. These results are suggestive of a magnetically inhomogeneous ferromagnetic state, that is, the formation of ferromagnetic clusters.

DOI： 10.1103/PhysRevB.79.224423

Pressure-induced superconductivity in the orthorhombic Kondo compound CePtSi2 Reviewed

Tomohito Nakano, Masashi Ohashi, Gendo Oomi, Kazuyuki Matsubayashi, Yoshiya Uwatoko

PHYSICAL REVIEW B 79 ( 17 ) 172507-1-4 2009.5

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

We have discovered a member of superconductivity induced by hydrostatic pressure in an antiferromagnetic (AF) concentrated Kondo compound CePtSi2 by measuring the resistivity and magnetoresistance. The AF transition temperature T-N of 1.8 K at ambient pressure is suppressed by pressure and disappears around 1.2 GPa. Above 1.4 GPa, a superconducting phase appears between 1.4 and 2.4 GPa, with the maximum T-c of 0.14 K at 1.7 GPa. The upper critical field of the superconductivity is evaluated to be 0.7 T, which is clearly larger than that of the Pauli limit predicted by the BCS theory.

DOI： 10.1103/PhysRevB.79.172507

Anisotropic Lattice Compression and Possible Valence Change in Kondo Compound CeAu_2Si_2

OHMURA Mio, SAKAI Kumiko, NAKANO Tomohito, MIYAGAWA Hidenori, OOMI Gendo, SATO Isamu, KOMATSUBARA Takemi, AOKI Haruyoshi, MATSUMOTO Yuji, UWATOKO Yoshiya

Journal of the Magnetics Society of Japan 33 ( 2 ) 31 - 34 2009.3

Language：English Publisher：The Magnetics Society of Japan (MSJ)

Lattice constants and crystal structure of tetragonal Kondo compound CeAu<sub>2</sub>Si<sub>2</sub> have been investigated at high pressure in order to examine pressure-induced change of crystal structure and gradual valence change of Ce atom. It is found that the lattice constants a and c decrease with increasing pressure without any discontinuity up to 13 GPa at room temperature. The bulk modulus <i>B</i><sub>0</sub> and its pressure derivative <i>B</i><sub>0</sub>' were obtained to be 112 GPa and 3.2. These values are comparable with other Kondo compounds. From the ρ(T) curve at high pressure which does not change so much under high pressure, it is suggested that the valence of Ce changes sluggishly with pressure and the Kondo state of CeAu<sub>2</sub>Si<sub>2</sub> is very stable at high pressure.

DOI： 10.3379/msjmag.0902LC8069

Partial Gap of SDW in Ce(Ru1-xRhx)2Si2 Reviewed

T. Nakano, S. Murayama, G. Oomi

Journal of the Magnetics Society of Japan 33 ( 2 ) 35-37 2009

Thermal expansion and magnetostriction of the concentrated Kondo compound CePtSi2 Reviewed

Tomohito Nakano, Gendo Oomi, Tetsuya Takeuchi

25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4 150 ( 4 ) 042139-1-4 2009

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

We measured the thermal expansion and magnetostriction of a polycrystalline concentrated Kondo compound CePtSi2, which has an orthorhombic CeNiGe2-type structure and the characteristic Kondo temperature T-K of 3 K. The linear thermal expansion dl/l decreases smoothly with decreasing temperature down to 2.5 K, and shows a rapid increase below 2 K due to antiferromagnetic ordering. The magnetostriction at 0.7 K shows an anomaly below 0.5 T, suggesting the disappearance of antiferromagnetic ordering.

DOI： 10.1088/1742-6596/150/4/042139

Hall effect in CeAl2 under high pressure Reviewed

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

25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4 150 ( 4 ) 042127-1-4 2009

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

We have measured the Hall effect of the single crystalline CeAl2 under high pressure up to 3 GPa. An anomalous Hall effect was observed at high pressures. The Hall coefficient R-H at 0.1 GPa is positive (R-H similar to 1.7 x 10(-9) m(3)/As). It decreases smoothly with increasing pressure below 2 GPa, but rapidly above 2 GPa. The sign of the Hall coefficient is found to change from positive to negative as pressure increases. These results suggest a pressure-induced crossover in the electronic state around 2.7 GPa.

DOI： 10.1088/1742-6596/150/4/042127

Nanoscale spin-dependent transport in a weak itinerant ferromagnet BaIrO3 Reviewed

Takanori Kida, Shunsuke Yoshii, Masayuki Hagiwara, Tomohito Nakano, Ichiro Terasaki

25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 2 150 ( 2 ) 022037-1-4 2009

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

We have performed magnetoresistance (MR) measurements for a BaIrO3 single crystal. As the magnetic field changes from 0 T to 14 T and back to 0 T, the longitudinal MR at 1.5 K traces out a butterfly-shaped hysteresis curve and the sign of the MR ratio for the field-ascending sweep changes from negative to positive near 6 T. The MR ratios for field-ascending and descending sweeps overlap each other around 13 T. A large anisotropic magnetoresistance (AMR) ratio per mu B, (rho parallel to - rho perpendicular to) rho(0) similar to 400 %/mu B at 1.5 K, is obtained, where rho parallel to, rho perpendicular to, and rho(0) are the longitudinal resistivity, the transverse resistivity, and the zero- field resistivity. The MR effects are interpreted based on a spin valve model considering a novel crystal structure and a local magnetic-anisotropy related to the spin-orbit coupling of this compound.

DOI： 10.1088/1742-6596/150/2/022037

Resistivity of antiferromagnetic compounds Ce0.8La0.2(Ru 1-xRhx)2Si2 Reviewed

S. Ishiuchi, H. Naruse, S. Murayama, Y. Amakai, T. Nakano, Y. Uwatoko

Journal of Physics: Conference Series 150 ( 4 ) 042072-1-4 2009

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

We have measured the susceptibility χ and resistivity ρ on single-crystalline Ce0.8La0.2(Ru1-xRh x)2Si2 in directions parallel and perpendicular () to the c-axis. The χ for each Rh concentration increases with decreasing temperature, and then rapidly decreases for x ≤ 0.2 and x ≥ 0.8, indicating the AF transition at the Néel temperature TN. The ρ for x 0 shows a cusp at around TN 5.5 K, however, ρ indicates a broad maximum at higher temperature than TN and a rapid decrease at much lower temperature than TN, without evidence of a gap-type AF ordering. The ρ for x 0.2 indicates a clear cusp at about T N. Such sharp anomaly in ρ once disappears for x 0.6 and is again observed at TN for x ≥0.8 probably due to another type of the AF ordering. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/150/4/042072

Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2-x Fex CrSi

Hiroi, M., Rokkaku, T., Matsuda, K., Hisamatsu, T., Shigeta, I., Ito, M., Sakon, T., Koyama, K., Watanabe, K., Nakamura, S., Nojima, T., Nakano, T., Chen, L., Fujiwara, T., Uwatoko, Y., Manaka, H., Terada, N.

Physical Review B - Condensed Matter and Materials Physics 79 ( 22 ) 2009

強相関酸化物BaIrO3 におけるモット絶縁体−電荷移動型絶縁体転移の圧力効果 Reviewed

中野智仁

高圧力の科学と技術 18 ( 1 ) 62-68 - 62 2008

Nonlinear thermoelectric properties of layered cobalt oxides Reviewed

Tomohito Nakano, Wataru Kobayashi, Ryoji Funahashi, Kenji Sugiura, Hiromichi Ohta, Kunihito Koumoto, Ichiro Terasaki

PROCEEDINGS ICT 07: TWENTY-SIXTH INTERNATIONAL CONFERENCE ON THERMOELECTRICS 121 - 123 2008

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

We synthesized whisker-crystal and thin-film samples of the layered cobalt oxide (Bi2Sr2O4)(x)CoO2 well known as a candidate of a thermoelectric material, and measured their resistivity, voltage-current characteristics and magnetoresistance with pulsed currents. Resistivity of the whisker sample with a small current density of 2 mA/cm(2) increases with decreasing temperature below 100 K, suggesting development of a pseudogap on the density of states. This increase is suppressed by a large current density of 110 A/cm(2). The nonlinear voltage-current characteristics are observed both for the whisker and thin-film samples. The negative magnetoresistance of the thin-film sample is suppressed by current density. These suggest that the density of states recovers owing to the suppression of the pseudogap by applying large current density.

DOI： 10.1109/ICT.2007.4569438

Unconventional critical behavior in the weak ferromagnet BaIrO<sub>3</sub> Reviewed

Kida, T., Senda, A., Yoshii, S., Hagiwara, M., Takeuchi, T., Nakano, T., Terasaki, I.

EPL 84 ( 2 ) 27004-1-4 2008

Dielectric constant and ac conductivity of the layered cobalt oxide Bi(2)Sr(2)CoO(6+delta): A possible metal-dielectric composite made by self-organization of Co(2+) and Co(3+) ions Reviewed

Y. Nagao, I. Terasaki, T. Nakano

PHYSICAL REVIEW B 76 ( 14 ) 144203-1-5 2007.10

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

The dielectric constant and ac conductivity of a single-crystal sample of the layered cobalt oxide Bi(2)Sr(2)CoO(6+delta) were measured along the c axis from 10(2) to 10(9) Hz from 110 to 300 K, the frequency dependence of which is found to be similar to that for metal-dielectric composites. The ac conductivity obeys the same scaling relation as that of disordered solids, which is quantitatively consistent with a theoretical calculation for spatially inhomogeneous conductive medium. This implies that the charge carrier on the Co(2+) site is electronically segregated in the CoO(2) plane. This compound can work as a metal-dielectric composite even in a form of single crystal, a possible mechanism of which is suggested on the basis of the electronic configuration of Co ions.

DOI： 10.1103/PhysRevB.76.144203

Positive and negative pressure effects on the magnetic ordering and the Kondo effect in the compound Ce2RhSi3 Reviewed

T. Nakano, Kausik Sengupta, Sudhindra Rayaprol, M. Hedo, Y. Uwatoko, E. V. Sampathkumaran

JOURNAL OF PHYSICS-CONDENSED MATTER 19 ( 32 ) 326205-1-13 2007.8

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

The competition between magnetic ordering and the Kondo effect in Ce2RhSi3, ordering antiferromagnetically at 7 K, is investigated by the measurements of magnetization, heat capacity and electrical resistivity on the solid solutions, Ce2-xLaxRhSi3, Ce2-yYyRhSi3, and Ce2RhSi3-zGez, as well as by high-pressure studies on this compound. The trends in the Kondo and Neel temperature variations among these alloys are compared to infer the roles of unit-cell volume and electronic structure changes. On the basis of the results, we infer that this compound lies at the peak of Doniach's magnetic phase diagram. The high-pressure electrical resistivity data indicate that the quantum critical point for this compound is in the vicinity of 4 GPa.

DOI： 10.1088/0953-8984/19/32/326205

Specific heat of superstoichiometric samarium dihydride (SmH2+delta) Reviewed

O. Nakamura, Y. Tanaka, K. Nakazawa, T. Nakano, M. Sakai, S. Orimo, Y. Uwatoko

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) E65 - E67 2007.3

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

We have investigated the specific heat and magnetic properties of superstoichiometric samarium dihydride (SmH2.16). The temperature (T) dependence of the specific heat (C-p) has three peaks at 7.1, 10.8 and 15.9 K. Below 7.1 K, C/ T is an almost linear function of T-2. The Sommerfeld coefficient gamma(LT) of the electronic specific heat below 7.1K is 150mJ= (K-2 mole). SmH2.16 exhibits coexistence of heavy- fermion behavior and magnetic ordering. The temperature dependence of the magnetic susceptibility can be explained by a valence ratio of 75% Sm3+, while the Shottky contribution of the specific heat can be explained by a valence ratio of 60% Sm3+. The reason why the amount of Sm3+ and the lattice constant of SmH2.16 are small compared with SmH2 is not yet clear. (c) 2006 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.244

Chemical pressure effect in the heavy fermion compound Ce1yLay(Ru0.85Rh0.15)(2)Si-2 Reviewed

Tsuyoshi Horii, Satomi Shimada, Tomohito Nakano, Shigeyuki Murayama, Hideaki Takano, Masato Hedo, Yoshiya Uwatoko

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) 313 - 315 2007.3

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

We have measured the susceptibility and resistivity on single-crystalline Ce1-yLa(y)(Ru0.85Rh0.15)(2)Si-2 along the tetragonal c-axis. The susceptibility increases with decreasing temperature, and then rapidly decreases, indicating the AF transition in each La concentration y. The resistivity also shows an anomaly in each La concentration y at around the T-N. For y <= 0.1, we observe a jump in resistivity just below TN as is seen for Ce( Ru0.85Rh0.15)(2)Si-2. This is interpreted in terms of the gap opening on the Fermi- surface along the c-axis. However, for y >= 0.2 the resistivity shows a downward bend at TN. These experimental facts suggest that the crossover from the spin density wave (SDW) with the gap opening to the localized AF order occurs at around y = 0.1. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.013

Magnetic field dependence of resistivity for Ce0.8La0.2(Ru0.85Rh0.15)(2)Si-2 Reviewed

Tomohito Nakano, Satomi Shimada, Shigeyuki Murayama, Masato Hedo, Yoshiya Uwatoko, Ichiro Terasaki

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) 402 - 404 2007.3

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

We measured resistivity of heavy fermion antiferromagnetic Ce0.8La0.2(Ru0.85Rh0.15)(2)Si-2 in magneticfield up to 4T. The resistivity for Ce0.8La0.2(Ru0.85Rh0.15)(2)Si-2 shows a downward bend at T-N, indicating an antiferromagnetic order with a local moment character. For 1T <= B <= 1.75 T, it shows a jump at T-N as in the case of Ce(Ru0.85Rh0.15)(2)Si-2, where the downward bend was no longer observed. This result indicates that instead of the local moment character, a gap is opened on the fermi surface by magnetic field. For B > 1.75 T, the resistivity is proportional to T-2 without any anomalies, suggesting that the developed gap closes again for B > 1.75 T, and the Fermi liquid state is induced by magnetic field. (c) 2006 Published by Elsevier B.V.

DOI： 10.1016/j.jmmm.2006.10.081

Nonlinear thermoelectric properties of layered cobalt oxides Reviewed

Tomohito Nakano, Wataru Kobayashi, Ryoji Funahashi, Kenji Sugiura, Hiromichi Ohta, Kunihito Koumoto, Ichiro Terasaki

International Conference on Thermoelectrics, ICT, Proceedings 26th 121 - 123 2007

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

We synthesized whisker-crystal and thin-film samples of the layered cobalt oxide (Bi2Sr2O4)xCoO2 well known as a candidate of a thermoelectric material, and measured their resistivity, voltage-current characteristics and magnetoresistance with pulsed currents. Resistivity of the whisker sample with a small current density of 2 mA/cm2 increases with decreasing temperature below 100 K, suggesting development of a pseudogap on the density of states. This increase is suppressed by a large current density of 110 A/cm2. The nonlinear voltage-current characteristics are observed both for the whisker and thin-film samples. The negative magnetoresistance of the thin-film sample is suppressed by current density. These suggest that the density of states recovers owing to the suppression of the pseudogap by applying large current density. © 2008 IEEE.

DOI： 10.1109/ICT.2007.4569438

Thermal expansion of CePt3Si under high pressure Reviewed

Masashi Ohashi, Gendo Oomi, Tomohito Nakano, Yoshlya Uwatoko

PHYSICA B-CONDENSED MATTER 378-80 379 - 380 2006.5

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

We have carried out the thermal expansion measurement of CePt3Si under pressure Lip to 3.0 GPa. It is found that a maximum in 1(T) is observed and the temperature showing maximum T increases significantly with increasing pressure having a coefficient partial derivative T-m/partial derivative P = 4 K/GPa. Assuming that T-m corresponds to the Kondo temperature T-K, partial derivative T-K/partial derivative P is smaller than that of typical heavy fermion compounds such as CeCu6. It comes from the fact that two kinds of interactions, the RKKY interaction and the Kondo effect, are competing each other. (c) 2006 Published by Elsevier B.V.

DOI： 10.1016/j.physb.2006.01.134

Giant nonlinear conduction and thyristor-like negative differential resistance in BaIrO3 single crystals Reviewed

Tomohito Nakano, Ichiro Terasaki

PHYSICAL REVIEW B 73 ( 19 ) 2006.5

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

We synthesized single-crystalline samples of monoclinic BaIrO3 using a molten flux method, and measured their magnetization, resistivity, Seebeck coefficient, and nonlinear voltage-current characteristics. The magnetization rapidly increases below the ferromagnetic transition temperature T-C of 180 K, where the resistivity concomitantly shows a hump-type anomaly, followed by a sharp increase below 30 K. The Seebeck coefficient suddenly increases below T-C, and shows linear temperature dependence below 50 K. A most striking feature of this compound is that the anomalously giant nonlinear conduction is observed below 30 K, where a small current density of 20 A/cm(2) dramatically suppresses the sharp increase in resistivity to induce a metallic conduction down to 4 K.

DOI： 10.1103/PhysRevB.73.195106

Thermal expansion and magnetostriction in YbInCu4 under high pressure Reviewed

Y. Saiga, T. Nakano, M. Hedo, Y. Uwatoko, M. Kosaka, N. Mori, T. Goto, K. Yoshimura

LOW TEMPERATURE PHYSICS, PTS A AND B 850 1177 - + 2006

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

YbInCu4 undergoes a first-order isostructural valence transition at T-V = 42K, which is accompanied by a 0.5% volume increase due to cooling. In order to elucidate the valence transition, both the linear thermal expansion and magnetostriction, Delta L/L, of a YbInCu4 single crystal were measured using strain gauges under high pressures of up to 3.0 GPa and a magnetic field of up to 18 T. The abrupt volume change during the valence transition was confirmed to decrease linearly with T-V under a high pressure. It was also observed that T-V was suppressed upon application of a magnetic field. On the basis of the results, we have established a T-P-B phase diagram for the first-order valence transition in YbInCu4.

DOI： 10.1063/1.2355123

Thermoelectronic properties of the strongly-correlated oxide BaIrO3 Reviewed

Tomohito Nakano, Ichiro Terasaki

ICT'06: XXV INTERNATIONAL CONFERENCE ON THERMOELECTRICS, PROCEEDINGS 25th(Pt. 2) 473 - + 2006

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

We synthesized polycrystalline samples of Ba1-xSrxIrO3 (0 <= x <= 0.2) using a solid-state reaction method, and measured their magnetization, resistivity, and thermopower. The thermopower of BaIrO3 slightly increases with decreasing temperature above T-C, and is suddenly enhanced below T-C = 180 K due to the pseudogap in the density of states. At 75 K, it reaches a maximum value of 230 mu V/K. With increasing Sr concentration, the thermopower systematically decreases, accompanied by a slight decrease of T-C. For x = 0.2, the maximum value of the thermopower and T-C are 50 mu V/K and 173 K, respectively. These results indicate that the gap is suppressed by chemical pressure due to the substitution of Sr for Ba.

DOI： 10.1109/ICT.2006.331318

Chemical pressure effect for the SDW phase in heavy fermion Ce(Ru0.85Rh0.15)(2)Si-2 compound Reviewed

T Nakano, H Yamashiro, K Fujita, S Murayama

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 5 ) 1602 - 1608 2005.5

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

Susceptibility measurements have been performed on polycrystalline samples Ce1-xRy(Ru0.85Rh0.15)(2)(-) Si-2 (R = Sc, La) in order to clarify the chemical pressure effect for the SDW in the heavy fermion Ce(Ru0.85Rh0.15)(2)Si-2. Lattice parameters a and c both decrease with increasing Sc concentration and increase with increasing La concentration. For Ce1-yScy(Ru0.85Rh0.15)(2)Si-2 system, the Neel temperature T-N decreases with increasing Sc concentration and disappears for y >= 0.2. We observed the Curie-Weiss law in the susceptibility at high temperature and a tendency of the saturation in the low temperature susceptibility. The tendency of the saturation and the Weiss temperature Theta determined from the high temperature susceptibility increase with increasing Sc concentration. These facts can be explained through the increase of the c-f hybridization and itinerancy of the f electron. For Ce1-yLay(Ru-0.85-Rh-0.15)(2)Si-2 system, the T-N slightly decreases with increasing La concentration and the tendency of the saturation becomes weaker with increasing y and is no more observed down to T-N for y > 0. 15. The Theta rapidly decreases with increasing La concentration and becomes almost zero for 37 > 0.15. These facts suggest that the c-f hybridization becomes weak with increasing y and that the itinerant AF phase for y < 0. 15 is replaced by the AF phase with the localized moment for y > 0. 15. The Kondo temperature T-K estimated from Theta is scaled by a single proportional function of the lattice parameter c in both cases for the Sc and La substitution.

DOI： 10.1143/JPSJ.74.1602

Magnetic phase transitions in PrCU2Ge2 Reviewed

T Shigeoka, K Hirata, T Nakano, Y Uwatokob

PHYSICA B-CONDENSED MATTER 359 923 - 925 2005.4

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

Measurements of electrical resistivity and specific heat have been performed on the tetragonal ternary compound PrCu2Ge2. The resistivity shows a inflection and a sharp drop with a hysteresis around 14 and 4K where the specific heat also shows lambda-type anomaly and a jump, respectively, which are associated with magnetic transitions. From the low temperature specific heat, the electronic specific heat coefficient y = 13 mJ/mol K-2 and the hyperfine field H-h = 3000 kOe are estimated. The magnetic entropy indicates the existence of a doublet ground level and a doublet first excited level. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.264

Electrical resistivity, specific heat and magnetic susceptibility of tetragonal CeGe1.66 Reviewed

T Nakano, M Hedo, Y Uwatoko

PHYSICA B-CONDENSED MATTER 359 284 - 286 2005.4

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

Magnetic susceptibility, specific heat and electrical resistivity measurements have been carried out on polycrystalline specimens of CeGe1.66, forming in a tetragonal structure, which is derived from CeGe2 by creation of vacancies at the Ge site. A shoulder in susceptibility, a jump in specific heat and an inflection in resisitivity attributable to magnetic ordering are observed at 6.7 K. Furthermore, a rapid increase in susceptibility, another jump in specific heat and a rapid decrease in the resistivity due to the ferromagnetic ordering are observed below (T-C =) 5.3 K. The electronic specific heat coefficient gamma is estimated to be about mJ/molK(2) (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.105

Resistivity of antiferromagnetic Ce0.8La0.2(Ru0.85Rh0.15)(2)Si-2 under pressure Reviewed

A Isoda, S Shimada, Y Kanda, S Murayama, H Takano, T Nakano, M Hedo, Y Uwatoko

PHYSICA B-CONDENSED MATTER 359 169 - 171 2005.4

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

We have measured the resistivity of antiferromagnetic Ce0.8La0.2(Ru0.85Rh0.15)(2)Si-2 along the tetragonal c-axis under various hydrostatic pressures. At P = 0 GPa we observe no gap-type jump in the resistivity at T-N as has been observed for Ce(Ru0.85Rh0.15)(2)Si-2 at the spin density-wave (SDW) transition temperature, but rather downward bend with decreasing temperature. At P >= 0.48GPa we observe the gap-type jump just below TN. These facts suggest the recovery of the gap opening due to the Fermi-surface nesting by pressure from a conventional localized antiferromagnetic state. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.025

Electrical resistivity and tunneling anomalies in CeCuAs2 Reviewed

EV Sampathkumaran, T Ekino, RA Ribeiro, K Sengupta, T Nakano, M Hedo, N Fujiwara, M Abliz, Y Uwatoko, S Rayaprol, T Doert, JPF Jernetio

PHYSICA B-CONDENSED MATTER 359 108 - 110 2005.4

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

The compound CeCuAs2 is found to exhibit negative temperature (T) coefficient of electrical resistivity (rho) under ambient pressure conditions in the entire T-range of investigation (45 mK-300 K), even in the presence of high magnetic fields. Preliminary tunneling spectroscopic measurements indicate the existence of a psuedo-gap at least at low temperatures, thereby implying that this compound could be classified as a Kondo semi-conductor, though rho(T) interestingly is not found to be of an activated type. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.005

Pressure-induced change in temperature coefficient of electrical resistivity in CeCuAS(2) Reviewed

M Abliz, T Nakano, EV Sampathkumaran, JPF Jemetio, T Doert, M Hedo, Y Uwatoko

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 2 ) 508 - 510 2005.2

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

The intermetallic compound, CeCuAs2, crystallizing in a HfCuSi2-type tetragonal structure, has recently been shown to exhibit a negative temperature (T) coefficient of electrical resistivity (p) in the entire T-range of investigation (45 mK to 300 K). Here, we report that an application of external pressure (up to IOGPa) profoundly influences p(T) behavior, reversing the sign of drho/dT at pressures above 8 GPa, presumably arising from increasing 4f hybridization or changes in pseudo-gap. Such a behavior is uncommon among Ce-based intermetallic compounds.

DOI： 10.1143/JPSJ.74.508

High pressure effects on the electrical resist ivity behavior of the Kondo lattice, YbPd2Si2 Reviewed

T Nakano, M Hedo, Y Uwatoko, EV Sampathkumaran

SOLID STATE COMMUNICATIONS 132 ( 5 ) 325 - 328 2004.11

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

We report the influence of external high-pressure (P up to 8 GPa) on the temperature (T) dependence of electrical resistivity (rho) of a Yb-based Kondo lattice, YbPd2Si2, which does not undergo magnetic ordering under ambient pressure condition. There are qualitative changes in the rho(T) behavior due to the application of external pressure. While rho is found to vary quadratically below 15 K (down to 45 mK) characteristic of Fermi-liquids, a drop is observed below 0.5 K for P = 1 GPa, signaling the onset of magnetic ordering of Yb ions with the application of P. The Tat which this fall occurs goes through a peak as a function of P (8 K for P = 2 GPa and about 5 K at high pressures), mimicking Doniach's magnetic phase diagram. We infer that this compound is one of the very few Yb-based stoichiometric materials, in which one can traverse from valence fluctuation to magnetic ordering by the application of external pressure. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ssc.2004.07.064

Magnetic, electrical resistivity, heat-capacity, and thermopower anomalies in CeCuAs2 Reviewed

K Sengupta, EV Sampathkumaran, T Nakano, M Hedo, M Abliz, N Fujiwara, Y Uwatoko, S Rayaprol, K Shigetoh, T Takabatake, T Doert, JPF Jemetio

PHYSICAL REVIEW B 70 ( 6 ) 2004.8

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

The results of magnetic susceptibility (chi), electrical resistivity (rho), heat-capacity (C), and thermopower (S) measurements on CeCuAs2, forming in the ZrCuSi2-type tetragonal structure, are reported. Our investigations reveal that Ce is trivalent and there is no clear evidence for long range magnetic ordering down to 45 mK. The rho behavior is notable in the sense that (i) the temperature (T)-coefficient of rho is negative in the entire range of measurement (45 mK to 300 K) with large values of rho, while the S behavior is typical of metallic Kondo lattices, and (ii) rho is proportional to T-0.6 at low temperatures, without any influence on the exponent by the application of a magnetic field, which does not seem to classify this compound into hither-to-known non-Fermi liquid (NFL) systems. In contrast to the logarithmic increase known for NFL systems, C/T measured down to 0.5 K exhibits a fall below 2 K. The observed properties of this compound are unusual among Ce systems.

DOI： 10.1103/PhysRevB.70.064406

Crystal structure and structural transition caused by charge-transfer phase transition for iron mixed-valence complex (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] (dto = C2O2S2) Reviewed

M Itoi, A Taira, M Enomoto, N Matsushita, N Kojima, Y Kobayashi, K Asai, K Koyama, T Nakano, Y Uwatoko, J Yamaura

SOLID STATE COMMUNICATIONS 130 ( 6 ) 415 - 420 2004.5

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

(n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] shows a new type of first order phase transition called chare-transfer phase transition around 120 K. where the charge transfer between Fe-II and Fe-III occurs reversibly. Recently, we have succeeded in obtaining single crystals of the title complex and determined the crystal Structure at room temperature. Crystal data: space group P6(3), a = 10.0618(5) Angstrom. c = 16.0424(7) Angstrom. V = 1406.54(12)Angstrom, Z = 2. Moreover. we have investigated the structural transition caused by the charge-transfer phase transition by means of powder X-ray diffraction measurement. When the temperature is decreased. the a-axis. which corresponds to the hexagonal ring size in two-dimensional honeycomb network structure of [Fe-II Fe-III(dto)(3)](infinity). contracts by 0.1 Angstrom at the charge-transfer transition temperature (T-CT) while the c-axis. perpendicular to the honeycomb network layer. elongates by 0.1 Angstrom at T-CT. Consequently, when the temperature is decreased, the unit cell volume decreases without noticeable anomaly around T-CT, which is responsible for the quite sniall vibrational contribution to the entropy change. compared with usual spin crossover transition. Thus, the charge-transfer phase transition around 120 K for (n-C3H7)(4)N[Fe-II Fe-III(dto)(3)] is regarded as spin entropy driven phase transition. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ssc.2004.02.034

Pressure effect and temperature dependence of lattice constants for Ce(Ru0.85Rh0.15)(2)Si-2 Reviewed

Kazuko Koyama, Tomohito Nakano, Masato Hedo, Yoshiya Uwatoko, Shigeyuki Murayama

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 ( 2 ) E109 - E110 2004.5

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

X-ray powder diffraction has been studied on Ce(Ru0.85Rh0.15)(2)Si-2 between 300 and 4 K under pressure up to 32 GPa with a diamond anvil cell, and the lattice constants and the bulk modulus have been obtained. The bulk modulus shows a rapid drop between 100 and 50 K; when the temperature decreases from 300 to 4 K: This tendency is most likely attributed to Kondo effect and/or a sign of a spin density wave. (C) 2003 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.11.217

Resistivity of Ce(Ru1-xRhx)(2)Si-2 under pressure Reviewed

Tomohito Nakano, Ayano Isoda, Masato Hedo, Yoshiya Uwatoko, Shigeyuki Murayama

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E85 - E86 2004.5

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

Resistivity measurement on single-srystalline Ce(Ru0.85Rh0.15)(2)Si-2 sample, which shows a spin-density-wave (SDW) transition at a Neel temperature T-N = 5.5 K; has been performed with excitation current parallel to tetragonal a-axis under hydrostatic pressure. Resistivity shows an inflection around T-N, although a hump-type anomaly is not observed as in the case for the c-axis. This in. ection shifts to lower temperature with increasing pressure. This result indicates that the gap of Fermi surface is open only along the c-axis direction up to P-c. On the other hand, the shoulder corresponding to the Kondo effect exists around T similar to 20 K; and shifts to higher temperature with increasing pressure, indicating an increase of T-K: This is consistent with the result for the c-axis. (C) 2004 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.11.314

Magnetic, electrical resistivity, heat-capacity, and thermopower anomalies in CeCuAs2 Reviewed

K. Sengupta, E. V. Sampathkumaran, T. Nakano, M. Hedo, M. Abliz, N. Fujiwara, Y. Uwatoko, S. Rayaprol, K. Shigetoh, T. Takabatake, T. Doert, J. P. F. Jeme

Physical Review B 70 ( 6 ) 064406-1-5 2004

Resistivity of Ce(Ru0.85Rh0.15)(2)Si-2 under pressure Reviewed

T Nakano, K Fujita, S Murayama, K Hoshi, M Hedo, Y Uwatoko

PHYSICA B-CONDENSED MATTER 329 532 - 534 2003.5

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

Resistivity measurement on single-crystalline Ce(Ru0.85Rh0.15)(2)Si-2 sample which shows a spin-density-wave (SDW) transition at a Neel temperature T-N = 5.5 K has been performed under hydrostatic pressure. A hump-type jump in resistivity due to the SDW transition shifts to lower temperature with increasing pressure, and finally disappears above P = 0.5 GPa. The ratio of gapped part of the Fermi-surface along the c-axis is estimated as similar to0.45 for P = 0 GPa and almost pressure independent. (C) 2003 Published by Elsevier Science B.V.

DOI： 10.1016/S0921-4526(02)02374-8

Specific heat of Ce(Ru1-xRhx)(2)Si-2 at around the SDW phase Reviewed

T Nakano, K Fujita, Y Ohmori, S Murayama, K Hoshi, H Amitsuka, Y Onuki, M Ocio, J Hammann

PHYSICA B-CONDENSED MATTER 312 440 - 442 2002.3

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

Specific heat measurements have been performed on single-crystalline Ce(Ru1-xRhx)(2)Si-2 (x = 0.15,0.35) in various magnetic fields parallel to the c-axis. For x = 0.15, the magnetic specific heat C,; shows a jump due to the spin density wave for B<B-c (similar to3.6T). For B-c<B<6T, C-mag/T increases with decreasing temperature with a non-Fermi liquid (NFL) behavior. The paramagnetic Fermi liquid (FL) behavior was observed for B > 6T. For x = 0.35, C-mag/T shows the NFL behavior for B<6T and the FL behavior for B>6T. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01358-8

Resistivity and susceptibility of heavy-fermion Ce(Ru1-xPdx)(2)Si-2 Reviewed

S Murayama, T Nakano, Y Ohmori, K Hatano, K Hoshi

PHYSICA B-CONDENSED MATTER 312 445 - 447 2002.3

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

Temperature dependence of the resistivity and susceptibility on single-crystalline Ce(Ru1-xPdx)(2)Si-2, x=0.08 has been measured in directions parallel and perpendicular to the c-axis in various magnetic fields along the c-axis. These results show clear anomalies at around T-N only in the parallel direction and suggest partial gapping of the Fermi surface along the c-axis due to a uniaxial Fermi-surface nesting. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)01165-6

Anomalous magnetic structures and properties in strongly correlated or competing metal and alloys Reviewed

S. Murayama, H. Takano, T. Nakano, Y. Ohmori, M. Ishida, T. Matusmura, K. Hoshi

Proceedings 2001-1 Symposium “Muon Science 2001”, ed. Y. Miyake, K. Nishiyama and K. Nagamine 124-131 2001

Magnetic properties of the heavy-fermion Ce(Ru1-xRhx)(2) Si-2 at the critical Rh concentration of the SDW phase Reviewed

T Nakano, Y Ohmori, S Murayama, K Hoshi, Y Onuki

PHYSICA B 281 346 - 348 2000.6

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

The resistivity and the susceptibility for Ce(Ru1-xRhx)(2)Si-2, x = 0.03,0.33 and 0.35 have been measured. For x = 0.33, an anomaly in the resistivity due to antiferromagnetic (AF) transition was observed and the paramagnetic Fermi liquid behaviors were observed in held B greater than or equal to 1 T. For x = 0.35, the resistivity shows disappearance of the anomaly due to the AF transition and follows A T-n. n = 1.4 at B = 0 T and n = 1.8 at B = 4 T. Finally, the B-x magnetic phase diagram has been proposed. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Magnetic properties of heavy-fermion Ce(Ru1-xPdx)(2)Si-2 Reviewed

S Murayama, C Sekine, S Yotsuya, T Nakano, Y Ohmori, K Hoshi, Y Tsuchiya, T Osakabe

PHYSICA B 281 343 - 345 2000.6

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

Magnetic structure of single-crystalline Ce(Ru1-xPdx)(2)Si-2, x = 0.025 has been measured by neutron diffraction. The magnetic moment is oriented and modulated along the c-axis with incommensurate wave vector tau = (0,0,0.368). At 1.4 K the moment was estimated to be about 0.15 mu(B). Temperature dependence of the specific heat on polycrystalline Ce(Ru1-xPdx)(2)Si-2, x = 0.05 has also been measured in various magnetic fields, suggesting partial gapping of the Fermi surface due to a Fermi-surface nesting. (C) 2000 Elsevier Science B.V. All rights reserved.

Magnetic properties of heavy-fermion Ce(RuPd)<sub>2</sub>Si<sub>2</sub>

Murayama, S., Sekine, C., Yotsuya, S., Nakano, T., Ohmori, Y., Hoshi, K., Tsuchiya, Y., Osakabe, T.

Physica B: Condensed Matter 281-282 2000

Spin-density-wave transition and mSR in the heavy-fermion Ce(Ru,T)2Si2, T = Rh, Pd. Reviewed

S. Murayama, C. Sekine, T. Nakano, Y. Tsuchiya, K. Nishiyama, K. Nagamine, Y. Onuki

JJAP Series 11 15-17 1999

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