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4. Materials

4.1 New Materials

4. 1. 2. Organic Superconductors, C60, and Related Materials

M. Tokumoto
-Electron Materials Lab. and Molecular Solids Lab.
E-mail madoka@etl.go.jp
(Last renewal Dec. 20, 1996)

Researchers

Superconducting Materials Section, Materials Science Division
M. Tokumoto, N. Kinoshita, Y. Tanaka, S. Ishibashi, T. Kinoshita
Visiting Researchers
M. E. Kozlov, Y. S. Song, L. S. Grigoryan, K. Pokhodnya
Student
Y. Tsubaki (Science University of Tokyo)

Research Activities

We are studying C60, or fullerenes, as a new member of molecular superconductors, in addition to the traditional organic superconductors based on planer p-conjugated molecules including BEDT-TTF. Isotope effect on intramolecular vibration is regarded as one of the most essential points in order to elucidate the mechanism of superconductivity in molecular superconductors, based on both BEDT-TTF and C60. Fermi surface study is now one of the most active subjects in the field of organic conductors and superconductors. -(BEDT-TTF) 2MHg(SCN)4 (M = K, Rb, NH4 and Tl) are isostructural and constitute one of the most interesting classes of organic conductors, in which the superconductivity (Tc = 1K for M = NH4) competes with an unidentified magnetic phase (M = K, Rb or Tl) at temperatures below about 10 K and under magnetic fields below about 30 Tesla in the T-H phase diagram. We have been studying the electronic and magnetic properties of (BEDT-TTF)2MHg(SCN)4 at low temperatures under high magnetic fields and high pressure in close collaboration with Prof. J. S. Brooks at the National High Magnetic Field Laboratory (NHMFL) of Florida State University (FSU) in the U.S.A., and Dr. H. Aoki at the National Research Institute for Metals (NRIM) in Japan. We also collaborate with Prof. H. Anzai at the Himeji Institute of Technology in Japan and Dr. P. Cassoux at Laboratoire de Chimie de Coordination (LCC) of CNRS in France.

  1. Growth of single crystals of organic conductors and superconductors
  2. Preparation and characterization of new C60-based materials
  3. Electron Spin Resonance study of organic and C60-based materials
  4. Optical study of organic and C60-based materials
  5. Transport and magnetic study of organic and C60-based materials
  6. Fermi surface study of molecular conductors and superconductors
  7. Positron states in both C60 and organic charge transfer salts



Fig.1. Growth of Single Crystals of Molecular Ferromagnet TDAE-C60 by Diffusion Method. (TDAE: Tetrakis(dimethylamino)ethylene). (Above) Crystal Growth Cell. (Below) Single Crystals of TDAE-C60. The bridge part is enlarged.

Publications(19951996)

  1. "Electronic Stucture of a Linear C60 Polymer"
    K. Tanaka, Y. Asai, Y. Matsuura, Y. Oshima, T. Yamabe and M. Tokumoto, Solid State Commun., 93 (2), 163-165 (1995.1).
  2. "Isotope Effect on Intramolecular Vibration of C60"
    Y. Tanaka, M. Tokumoto and Y. Sugawara, Fullerene Science and Technology 3 (2), 179-223 (1995.3).
  3. "Transformation of C60 fullerenes into a superhard form of carbon at moderate pressure"
    M.E. Kozlov, M. Hirabayashi, K. Nozaki, M. Tokumoto, H. Ihara, Appl. Phys. Lett., 66 (10), 1199-1201 (1995.3.6).
  4. "Effect of anion ordering in the superconducting phase of (TMTSF)2ClO4"
    N. Matsunaga, H. Takeshige, R. Okajima, A. Hoshikawa, K. Nomura, T. Sambongi, M. Tokumoto, N. Kinoshita, H. Anzai, Synthetic Metals 70 (1-3), 763-764 (1995.3.15).
  5. "Uniaxial stress study of the magnetotransport properties of the quasi-two dimensional organic conductor -(BEDT-TTF) 2KHg(SCN)4"
    C. E. Campos, J. S. Brooks, P. J. M. van Bentum, J. A. A. J. Perenboom, S. J. Klepper, P. Sandhu, M. Tokumoto, T. Kinoshita, N. Kinoshita, Y. Tanaka and H. Anzai, Synthetic Metals 70 (1-3), 803-806 (1995.3.15).
  6. "Fermi Surface Reconstruction in (BEDT-TTF)2TlHg(SCN)4"
    S. Uji, T. Terashima, H. Aoki, J.S. Brooks, M. Tokumoto, N. Kinoshita, T. Kinoshita, Y. Tanaka, H. Anzai, Synthetic Metals 70 (1-3), 807-810 (1995.3)
  7. "Electrical Anisotropy of -(BEDT-TTF) 2KHg(SCN)4"
    M. Arifuku, H. Tajima, T. Ohta, M. Tokumoto, N. Kinoshita, H. Anzai, Synthetic Metals 70 (1-3), 827-828 (1995.3.15).
  8. "Angular Magnetoresistance Oscillations and Magnetic Breakdown in -(BEDT-TTF) 2I3"
    S. J. Klepper, G. J. Athas, J. S. Brooks, M. Tokumoto, M. Tamura, M. Kinoshita, Synthetic Metals 70 (1-3), 835-836 (1995.3.15).
  9. "Pressure effects on the low temperature state of the -(BEDT-TTF) 2MHg(SCN)4 organic conductor family"
    X. Chen, J. S. Brooks, S. J. Klepper, S. Valfells, G. J. Athas, M. Tokumoto, N. Kinoshita, Y. Tanaka, H. Anzai, Synthetic Metals 70 (1-3), 837-838 (1995.3.15).
  10. "Anisotropic Hc2, Shubnikov de Haas, and angular dependent magnetoresistance in the organic superconductor -(BEDT-TTF)2MHg(SCN)4"
    J. S. Brooks, S. Uji, H. Aoki, T. Terashima, M. Tokumoto, N. Kinoshita, Y. Tanaka, H. Anzai, Synthetic Metals 70 (1-3), 839-840 (1995.3.15).
  11. "Angular Dependence of the High Field Phase Transition in -(BEDT-TTF) 2TlHg(SCN)4"
    G. J. Athas, S. J. Klepper, J. S. Brooks, M. Tokumoto, T. Kinoshita, N. Kinoshita, Y. Tanaka, H. Anzai, Synthetic Metals 70 (1-3), 843-844 (1995.3.15).
  12. "Reexamination of Angle Dependent Magnetoresistance Oscillation in -(BEDT-TTF)2I3"
    T. Terashima, S. Uji, H. Aoki, M. Tamura, M. Kinoshita and M. Tokumoto, Synthetic Metals 70 (1-3), 845-846 (1995.3.15).
  13. "The Shubnikov de Haas Oscillation and a Small Closed Orbit in -(BEDT-TTF) 2I3"
    T. Terashima, S. Uji, H. Aoki, M. Tamura, M. Kinoshita and M. Tokumoto, Synthetic Metals 70 (1-3), 847-848 (1995.3.15).
  14. "Calculation of positron states in BEDT-TTF based organic superconductors"
    S. Ishibashi, M. Tokumoto, N. Kinoshita, N. Terada, H. Ihara, Synthetic Metals 70 (1-3), 953-954 (1995.3).
  15. "Photoluminescence of BEDT-TTF and its ion radical salt"
    M. E. Kozlov, Y. Tanaka, M. Tokumoto, T. Tani, Synthetic Metals 70 (1-3), 987-988 (1995.3.15)
  16. "Using a dimer approach to examine the electron-molecular vibration couplimg in BEDT-TTF based charge-transfer salts"
    M. E. Kozlov, M. Tokumoto, Synthetic Metals 70 (1-3), 1023-1024 (1995.3.15).
  17. "Structure and Magnetic Properties of Halogen-doped C60"
    M. Tokumoto, N. Kinoshita, Y. Tanaka, S. Ishibashi, H. Ihara, H. Sekine, H. Maeda, Synthetic Metals 70 (1-3), 1387-1388 (1995.3.15).
  18. "Superhard form of carbon obtained from C60 at moderate pressure"
    M.E. Kozlov, M. Hirabayashi, K. Nozaki, M. Tokumoto, H. Ihara, Synthetic Metals 70 (1-3), 1411-1412 (1995.3.15).
  19. "New Results on Molecular Inorganic and Organic Conductors"
    P. Cassoux, L. Brossard, M. Tokumoto, H. Kobayashi, A. Moradpour, D. Zhu, M. Mizuno and E. Yagubskii, Synthetic Metals 71 (1-3), 1845-1848 (1995.4.1).
  20. "Suppression of insulating state in (BETS)2FeCl4 by magnetic field"
    F. Goze, V. N. Laukhin, L. Brossard, A. Audouard, J.P. Ulmet, S. Askenazy, T. Naito, H. Kobayashi, A. Kobayashi, M. Tokumoto and P. Cassoux, Synthetic Metals 71 (1-3), 1901-1902 (1995.4.1).
  21. "Shubnikov-de Haas Measurements of Highly Pressurized (ET)2TlHg(SCN)4"
    S. Valfells, J. S. Brooks, S. W. Tozer, S. J. Klepper, Y. Tanaka, T. Kinoshita, N. Kinoshita, M. Tokumoto and H. Anzai, Solid State Commun., 94 (7), 499-502 (1995).
  22. "Superconductivity and Localization in the Density Wave State of -(BEDT-TTF) 2MHg(SCN)4 Organic Conductor Family"
    J. S. Brooks, S.J. Klepper, X. Chen, P. Henning, P.J. Signore, N.W. Meisel, N. Kinoshita, M. Tokumoto and H. Anzai, Applied Superconductivity 2 (7/8), 1-8 (1995).
  23. "Angular and magnetic field dependencies of the magnetoresistance of l-(BETS)2FeCl4 in the field-restored high conductivity state"
    F. Goze, V. N. Laukhin, L. Brossard, A. Audouard, J. P. Ulmet, S. Askenazy, T. Naito, H. Kobayashi, A. Kobayashi, M. Tokumoto and P. Cassoux, Physica B 211, 290-292 (1995.5.1).
  24. "Uniaxial-stress-study of the transport properties of the quasi-two-dimensional organic superconductor (BEDT-TTF)2Cu(NCS)2"
    C. E. Campos, J. S. Brooks, P. J. M. van Bentum, J. A. A. J. Perenboom, S. J. Klepper, P. S. Sandhu, S. Valfells, Y. Tanaka, T. Kinoshita, N. Kinoshita, M. Tokumoto and H. Anzai, Physica B 211, 293-296 (1995.5.1).
  25. "ac magnetic susceptibility of TDAE-C60"
    K. Tanaka, T. Sato, K. Yoshizawa, K. Okahara, T. Yamabe and M. Tokumoto, Chem. Phys. Letters 237, 123-126 (1995.5.5).
  26. "Specific Heat of the Organic conductor -(BEDT-TTF) 2MHg(SCN)4 (for M = K, Rb): Thermodynamic Evidence for a Low Temperature Phase Transition"
    P. Henning, J. S. Brooks, J. E. Crow, Y. Tanaka, T. Kinoshita, N. Kinoshita, M. Tokumoto and H. Anzai, Solid State Commun., 95 (10) , 691- (1995.9)
  27. "New Iodine Containing Polymers of C60: Synthesis, Characterization and Magnetic Properties"
    L. S. Grigoryan and M. Tokumoto, Solid State Commun., 96 (7) 523-528 (1995.11).
  28. "Uniaxial-Stress-Induced Superconductivity in Organic Conductors"
    C. E. Campos, J. S. Brooks, P. J. M. van Bentum, J. A. A. J. Perenboom, S. J. Klepper, P. S. Sandhu, S. Valfells, Y. Tanaka, T. Kinoshita, N. Kinoshita, M. Tokumoto and H. Anzai, Phys. Rev. B 52 (10) R7014-R7017 (1995.9.1).
  29. "Spectroscopic Investigation of High-Pressure Phases of C60 Fullerene"
    M. Kozlov, S. Kazaoui, N. Minami, K. Yakushi and M. Tokumoto, Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials: Electrochemical Society Proceedings Vol.95-10, p.90-98, ed.by R.S. Ruoff and K.M. Kadish (The Electrochenmical Society Inc., 1995).
  30. "Study of the Superhard Form of Carbon prepared from C60 Fullerene"
    M. Kozlov, K. Yase, N. Minami, P. Fons, H.-A. Durand, M. Hirabayashi, M. Tokumoto and H. Ihara, Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials: Electrochemical Society Proceedings Vol.95-10, p.99-107, ed.by R.S. Ruoff and K.M. Kadish (The Electrochenmical Society, 1995).
  31. "New Iodine Containing Polymers of C60: Synthesis, Characterization and Magnetic Properties"
    L.S. Grigoryan and M. Tokumoto, Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials: Electrochemical Society Proceedings Vol.95-10, p.807-822, ed.by R.S. Ruoff and K.M. Kadish (The Electrochenmical Society, 1995).
  32. "Superconductivity in C60-Based Polymer Doped with Alkali Metals"
    L.S. Grigoryan and M. Tokumoto, Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials: Electrochemical Society Proceedings Vol.95-10, p.1039-1048, ed.by R.S. Ruoff and K.M. Kadish (The Electrochenmical Society, 1995).
  33. "Pressure Effectd on the Electronic Structure and Low-Temperature States in the -(BEDT-TTF) 2MHg(SCN)4 Organic-Conductor Family (M = K, Rb, Tl, NH4)"
    J.S. Brooks, X. Chen, S.J. Klepper, S. Valfells, G.J. Athas, Y. Tanaka, T. Kinoshita, N. Kinoshita, M. Tokumoto, H. Anzai and C.C. Agosta, Phys. Rev. B 52 (20) 14457-14478 (1995.11.15).
  34. "Thermal Transport in Hard Carbon Prepared from C60 Fullerence"
    K. Biljakovic, A. Smontara, D. Staresinic, D. Pajic, M.E. Kozlov, M. Hirabayashi, M. Tokumoto, H. Ihara, J. Phys.: Condens. Matter 8, L27-32 (1996.1.15).
  35. "Evolution of Superconducting and Normal-state Properties in C60 Polymer"
    L.S. Grigoryan and M. Tokumoto, Fullerene Science & Technology 4 (1), 115-129 (1996.1.31).
  36. "Irreversible and Time-Dependent Magnetization in TDAE-C60"
    M. Tokumoto, Y.S. Song, K. Tanaka, T. Sato and T. Yamabe, Solid State Commun., 97 (5) 349-354 (1996.2.1).
  37. "Magnetic Interactions in TDAE-C60, where TDAE is Tetrakis(dimethylamino)ethylene"
    Y. Asai, M. Tokumoto, K. Tanaka, T. Sato and T. Yamabe, Phys. Rev. B 53 (7), 4176-4179 (1996.2.15).
  38. "Observation of Diamond Crystallites in Thin Films Prepared by Laser Ablation of Hard Fullerene-Based Carbon"
    M. Kozlov, K. Yase, N. Minami, P. Fons, H.-A. Durand, A.N. Obraztsov, K. Nozaki and M. Tokumoto, J. Phys. D: Appl. Phys., 29 (3), 929-933 (1996.3.14).
  39. "Applications of pulsed magnetic fields and low temperatures to low-dimensional (organic) conductor physics"
    J. S. Brooks, R. G. Clark, R. P. Starrett, R. Newbury, R. H. McKenzie, A. V. Skougarevsky, M. Tokumoto, N. Kinoshita, T. Kinoshita, Y. Tanaka, H. Anzai, S. Takasaki, J. Yamada, M. V. Kartsovnik, A. I. Shegolev, G. J. Athas, and P. Sandhu, Physica B 216, 380-383(1996).
  40. "Thermal Conductivity of Hard Carbon Prepared from C60 Fullerence"
    A. Smontara, K. Biljakovic, D. Staresinic, D. Pajic, M.E. Kozlov, M. Hirabayashi, M. Tokumoto, H. Ihara, Physica B 219&220, 160-162 (1996)
  41. "Comparative NMR Study of New Carbon Forms"
    Y. Maniwa, M. Sato, K. Kume, M. E. Kozlov, M. Tokumoto, Carbon 34 (10), 1287-1291 (1996).
  42. "ESR Study of High-Pressure Phases of C60 Fullerene"
    M. E. Kozlov, A. A. Zakhidov, K. Yakushi, M. Tokumoto, physica status solidi (b), 197, 187-194 (1996).
  43. "Magneto-oscillations and field-induced phase transitions in organic conductors"
    R. H. McKenzie, J. S. Brooks, R. G. Clark, R. Newbury, R. P. Starrett, A. Skougarevsky, R. A. Lewis, S. Takasaki, J. Yamada, H. Anzai, Y. Tanaka, T. Kinoshita, N. Kinoshita, M. Tokumoto, and N. D. Kushch, Surface Science 361/362, 901-904 (1996)
  44. " High-field Shubnikov-de Haas effect in the organic superconductor -(BEDT-TTF) 2NH4Hg(SCN)4"
    P. S. Sandhu, G. J. Athas, J. S. Brooks, E. Haanappel, J. D. Goettee, D. Rickel, M. Tokumoto, N. Kinoshita, T. Kinoshita, and Y. Tanaka, Surface Science 361/362, 913-917 (1996).
  45. "Molecular Conductors : The Mesopotamia of Low-Dimensional Physics"
    J. S. Brooks, S. Uji, H. Aoki, R. Kato, H. Sawa, R. G. Clark, R. McKenzie, G. J. Athas, P. Sandhu, S. Valfells, C. E. Campos, J. A. A .J. Perenboom, P. J. M. van Bentum, M. Tokumoto, N. Kinoshita, T. Kinoshita, Y. Tanaka, H.Anzai, Z. Fisk, and J. Sarrao, : Proceedings of Physical Phenomena at High Magnetic Fields-II, 249-265, Eds. Z. Fisk, L. Gorkov, D. Meltzer, R. Schrieffer (World Scientific, 1996) .
  46. "Magnetic Breakdown in an Organic Conductor"
    C. C. Agosta, C. H. Mielke, S. A. Ivanov, D. A. Howe, J. D. Goettee, M. Tokumoto, Y. Tanaka and N. Kinoshita, Proceedings of Physical Phenomena at High Magnetic Fields-II, 297-302, Eds. Z. Fisk, L. Gorkov, D. Meltzer, R. Schrieffer (World Scientific, 1996).
  47. "Angular Studies in the -(ET) 2MHg(XCN)4 System Below 1K"
    I. J. Lee, V. N. Laukhin, N. D. Kushch, J. S. Brooks, M. Tokumoto, M. J. Naughton, Proceedings of Physical Phenomena at High Magnetic Fields-II, 350, Eds. Z. Fisk, L. Gorkov, D. Meltzer, R. Schrieffer (World Scientific, 1996).
  48. "T-H Phase Diagram of Organic Conductor l-(BETS)2FeCl4 By Magnetization and Magnetotransport Measurements"
    D. K. Petrov, A. P. Hope, I. J. Lee, M. J. Naughton, V. N. Laukhin, L. Brossard, T. Naito, H. Kobayashi, A. Kobayashi, M. Tokumoto, P. Cassoux, Proceedings of Physical Phenomena at High Magnetic Fields-II, 351, Eds. Z. Fisk, L. Gorkov, D. Meltzer, R. Schrieffer (World Scientific, 1996).
  49. "Magnetic Properties of TDAE-C60: Remanence and Relaxation"
    M. Tokumoto, Y. S. Song, K. Tanaka, T. Sato and T. Yamabe, Mat. Res. Soc. Proc., Vol.413, 333-338, Electrical, Optical, and Magnetic Properties of Organic Solid State Materials III, Eds. A. K-Y. Jen, C. Y-C Lee, L.R. Dalton, M.F. Rubner, G.E. Wnek, L.Y. Chiang (1996).
  50. "Superconductivity and Magnetism in C60 Polymer"
    L. S. Grigoryan and M. Tokumoto, Mat. Res. Soc. Proc., Vol.413, 665-670, Electrical, Optical, and Magnetic Properties of Organic Solid State Materials III, Eds. A. K-Y. Jen, C. Y-C Lee, L. R. Dalton, M. F. Rubner, G. E. Wnek, L.Y. Chiang (1996).
  51. "New BETS Superconductors and Metals with Tetrahedral Non-Magnetic and Magnetic Anions (BETS=Bis(ethylenedothio) tetraselenafulvalene)"
    H. Kobayashi, T. Naito, A. Sato, K. Kawano, A. Kobayashi, H. Tanaka, T. Saito, M. Tokumoto, L. Borossard, P. Cassoux, Molecular Crystals and Liquid Crystals 284, 61-72 (1996).
  52. "Rapid Oscillations in the Organic Conductor (TMTSF)2ClO4"
    S. Uji, T. Terashima, H. Aoki, J. S. Brooks, M. Tokumoto, S. Takasaki, Y. Yamada, and H. Anzai, Phys. Rev. B 53 (21), 14399-14405 (1996.6.1).
  53. "Magneto-oscillations in the high-magnetic-field state of (TMTSF)2ClO4"
    J. S. Brooks, R. G. Clark, R. McKenzie, R. Newbury, R. P. Starrett, A. V. Skougarevsky, M. Tokumoto, S. Takasaki, J. Yamada, H. Anzai, and S. Uji, Phys. Rev. B 53 (21), 14406-14410 (1996.6.1).
  54. "Fermi Surface Studies in the Two-Dimensional Organic Conductors (BEDT-TTF)2MHg(SCN)4 (M = Tl, K,. Rb, NH4)"
    S. Uji, T. Terashima, H. Aoki, J. S. Brooks, M. Tokumoto, N. Kinoshita, Y. Tanaka, and H. Anzai, Phys. Rev. B 54 (13), 9332-9340 (1996.10.1).
  55. "Molecular Metals Based on BETS and Magnetic Anions - l- and -BETS2FeCl4 and q-BETS4Cu2Cl6"
    H. Kobayashi, A. Kobayashi, T. Naito, M. Tokumoto, L. Brossard, N. Kushch and P. Cassoux, Molecular Crystals and Liquid Crystals 285, 11-18 (1996).
  56. "Magnetic Properties of Powder and Crystalline TDAE-C60"
    M. Tokumoto, K. Tanaka, T. Sato, T. Yamabe, A. Omerzu, K. Pokhodnya, D. Mihailovic, Fullerenes and Fullerene nanostructures, 535-538, Eds. H. Kuzmany, J. Fink, M. Mehring, S. Roth (World Scientific, 1996).