Single-Component Molecular Conductor [Cu(dmdt)<sub>2</sub>] with Three-Dimensionally Arranged Magnetic Moments Exhibiting a Coupled Electric and Magnetic Transition

  • Biao Zhou
    Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-Ku, Tokyo 156-8550, Japan
  • Yuki Idobata
    Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-Ku, Tokyo 156-8550, Japan
  • Akiko Kobayashi
    Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-Ku, Tokyo 156-8550, Japan
  • HengBo Cui
    Condensed Molecular Materials Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
  • Reizo Kato
    Condensed Molecular Materials Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
  • Rina Takagi
    Department of Applied Physics, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
  • Kazuya Miyagawa
    Department of Applied Physics, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
  • Kazushi Kanoda
    Department of Applied Physics, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
  • Hayao Kobayashi
    Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-Ku, Tokyo 156-8550, Japan

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Description

Crystals of the single-component molecular conductor [Cu(dmdt)(2)] (dmdt = dimethyltetrathiafulvalenedithiolate) were prepared as a molecular system, with three-dimensionally arranged magnetic moments embedded in "sea" of π conduction electrons. [Cu(dmdt)(2)] had fairly large room-temperature conductivity (110 S cm(-1)) and exhibited weakly metallic behavior near room temperature. Below 265 K, the resistivity (R) increased very slowly with decreasing temperature and then increased rapidly, indicating a transition from a highly conducting state to an insulating state near 95 K. The magnetic susceptibility showed Curie-Weiss behavior at 100-300 K (C = 0.375 emu/mol, Θ = 180 K). The Curie constant and the high-temperature resistivity behavior indicate that conduction electrons and three-dimensionally arranged magnetic moments coexist in the crystal. The ESR intensity increased down to about 95 K. The ESR signal was broadened and decreased abruptly near 95 K, suggesting that electric and antiferromagnetic transitions occurred simultaneously near 95 K. The crystal structure was determined down to 13 K. To examine the stability of the twisted conformation of Cu complex with dithiolate ligands, the dihedral angle dependence of the conformational energy of an isolated M(L)(2)(n-) molecule was calculated, which revealed the dihedral angle dependence on the ligand (L) and the oxidation state of the molecule (n). High-pressure four-probe resistivity measurements were performed at 3.3-9.3 GPa using a diamond anvil cell. The small resistivity increase observed at 3.3 GPa below 60 K suggested that the insulating transition observed at ambient pressure near 95 K was essentially suppressed at 3.3 GPa. The intermolecular magnetic interactions were examined on the basis of simple mean field theory of antiferromagnetic transition and the calculated intermolecular overlap integrals of the singly occupied molecular orbital (SOMO) of Cu(dmdt)(2).

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