2005 Fiscal Year Final Research Report Summary
Design and development of metallic crystals composed of single-component molecules
| Project/Area Number |
14103005
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| Research Category |
Grant-in-Aid for Scientific Research (S)
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| Allocation Type | Single-year Grants |
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| Research Field |
機能・物性・材料
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KOBAYASHI Akiko The University of Tokyo, Research Centre for Spectrochemistry, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (50011705)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIWARA Emiko The University of Tokyo, Research Centre for Spectrochemistry, Graduate School of Science, Research Assistant, 大学院・理学系研究科, 助手 (30361562)
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| Project Period (FY) |
2002 – 2005
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| Keywords | Single-Component Molecular Metals / Molecular Conductors / Dithiolate Metal Complex / Antiferromagnetic Phase Transition / Molecular Alloy Systems / Three-Dimensional Fermi Surfaces |
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| Research Abstract |
In this work, in order to realize the single-component metallic molecular magnets and molecular superconductors with various extended-TTF ligands, the structures, physical properties and molecular functions of a series of new developed single-component complexes were investigated.
To obtain direct evidence for the existence of Fermi surfaces in the first neutral metal complex molecule [Ni(tmdt)_2] (tmdt=trimethylenetetrathiafulvalenedithiolate), we have carried out experiments to measure magnetic quantum oscillations, namely de Haas-van Alphen (dHvA) oscillations, in high magnetic fields up to 33 T using a microcantilever. The observation of the dHvA signal in [Ni(tmdt)_2] demonstrates that it is a single-component molecular crystal which not only shows metallic conductivity behavior down to low temperatures, but also exhibits high-quality quantum oscillations characteristic of a Fermi surface. These results unambiguously show the existence of 3D Fermi surfaces for both holes and electr
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ons in this molecular crystal.
To create the single-component metallic molecular magnets with a high transition temperature, [Au(tmdt)_2] was developed, which is isostructural to that of [Ni(tmdt)_2]. Unlike the neutral bis (dithiolato) nickel complex, the neutral bis (dithiolato) gold complex has an odd number of total electrons. The spin susceptibilities study of [Au(tmdt)_2] showed an unusual antiferromagnetic phase transition around 110K, which is higher than that of the classical antiferromagnetic metal Mn around 100K. More recently, the metallic behavior down to phase transition temperature was observed by the resistivity measurements on a microcrystal of [Au(tmdt)_2], which indicate that the single-component metallic molecular magnets have been realized.
Since the Fermi surfaces of [Ni(tmdt)_2] are quite different from those of [Au(tmdt)_2], the molecular alloy system will be expected to be the single-component molecular superconductor. We have succeeded to prepare the first "single-component alloy system" [Ni_<1-x>Au_x(tmdt)_2](0<x<1). The resistivity of single crystal of [Ni_<0.75>Au_<0.25>(tmdt)_2] was abruptly deceasing below 2K, and the magnetic susceptibility was also slightly decreasing at the temperature range form 1.8 to 0.8K, which maybe stem from the partially appeared superconducting state. We think the "single-component molecular superconductor" may be realized in such an alloy system. Less
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