Faculty Profiles - NAKANO Tomohito

Papers - NAKANO Tomohito

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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

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