一个单元分子导体 [Cu(dmdt) 2 ],具有三维排列的磁矩,表现出合的电磁转换
Biao Zhou1, Yuki Idobata, Akiko Kobayashi
1Department of Chemistry, College of Humanities and Sciences, Nihon University, Setagaya-Ku, Tokyo, Japan.
Journal of the American Chemical Society
|July 5, 2012
概括
这项研究探讨了分子导体[Cu(dmdt) 2],揭示了其传导电子和磁矩的独特共存. 它从导电过渡到95K附近的绝缘状态,同时发生电和反铁磁变化.
科学领域:
- 材料科学 材料科学 材料科学
- 凝聚物质物理学 凝聚物质物理学
- 固态化学 固态化学
背景情况:
- 单元分子导体为研究电子和磁性特性相互作用提供了一个平台.
- 分子[Cu(dmdt) 2 (dmdt=二甲基四甲基三甲基多乙酸盐) 集成磁矩与π导电电子.
- 了解这些材料的相变对于开发新型电子和自旋电子设备至关重要.
研究的目的:
- 为了研究[Cu(dmdt) 2晶体的电磁性质.
- 为了确定导电性,磁性排序和结构过渡之间的关系.
- 探索高压对观察到的相变的影响.
主要方法:
- [Cu(dmdt) 2]单晶的合成和表征.
- 取决于温度的电阻和磁感应度的测量.
- 电子自旋共振 (ESR) 光谱学.电子自旋共振 (ESR) 光谱学.
- 在低温下进行X射线晶体学.
- 分子构成的计算分析.
- 使用钻石细胞测量高压电阻.
主要成果:
- [Cu(dmdt) 2 显示室温导电性为 110 S cm(-1) 具有弱金属行为.
- 过渡到绝缘状态发生在95K附近,并伴随着同时电和反铁磁排序.
- 磁性敏感性遵循100-300 K的库里-韦斯行为 (C = 0.375 emu/mol, Θ = 180 K)
- 高压 (3.3 GPa) 抑制了在环境压力下观察到的绝缘过渡.
- 形态分析揭示了连接体和氧化状态对分子结构的依赖.
结论:
- [Cu(dmdt) 2 的晶体结构促进了导电电子和3D磁矩的共存.
- 在95K附近的环境压力下,同时发生电和反铁磁过渡.
- 高压显著改变了电子和磁相的行为,抑制了绝缘过渡.
相关概念视频
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:26Diamagnetism
Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:31Ferromagnetism
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01:30Paramagnetism
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...