Physical properties of electrically conducting and stable molecular neutral radical solid [Co(2,3-Nc)(CN)2]CH3CN (2,3-Nc = 2,3-naphthalocyanine)
Physical properties of electrically conducting and stable molecular neutral radical solid [Co(2,3-Nc)(CN)2]CH3CN (2,3-Nc = 2,3-naphthalocyanine)
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DOI：
10.1142/s1088424604000611
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发表时间：
2004-12
影响因子：
1.5
通讯作者：
T. Naito;Naoko Matsumura;T. Inabe;Masaki Matsuda;H. Tajima
中科院分区：
文献类型：
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作者：
T. Naito;Naoko Matsumura;T. Inabe;Masaki Matsuda;H. Tajima
通过测量[Co(2，3-NC)(CN)2]CH3CN的高压和单轴应变下的电阻率、热电势、磁化率、ESR和偏振反射光谱，表征了二氰基(2，3-萘基)钴(III)中性自由基晶体的固态性质。标题化合物沿c轴具有热激活型导电性。室温(Rt)、c轴方向的电阻率ρ、Rt和激活能Ea随压力的增加而迅速减小。S的温变温差电势是典型的一维半导体温差电势。然而，S的高绝对值表明，这个电子系统应该是强关联的。虽然电阻率随温度的变化单调，但磁化率明显地表现为Peierls类型的转变，并且从RT开始有明显的波动。Peierls跃迁和涨落都是一维导体的特征现象。此外，ESR谱表明该材料在100K发生了Peierls类型的转变。电学行为(没有相变)和磁性行为(有相变)之间的不一致表明该材料的自旋和电荷自由度分离(自旋-电荷分离)。自旋-电荷分离是一维强关联导体所特有的一种理论预测现象。反射光谱用一维Hubbard模型进行了定量解释，从RT可以看出该材料存在结构涨落。根据这些观察到的物理性质，[Co(2，3-NC)(CN)2]CH3CN是一种具有Mott(Hubbard)型能隙的强关联一维半导体，具有涨落和自旋-电荷分离的特征。
Solid state properties of dicyano(2,3-naphthalocyaninato)cobalt(III) neutral radical crystal, [Co(2,3-Nc)(CN)2]CH3CN, were characterized by measurements of the resistivity under high pressure and under uniaxial strain, thermoelectric power, magnetic susceptibility, ESR and polarized reflectance spectra. The title compound exhibited thermally activated-type electrical conductivity along the c-axis. The room temperature (RT) resistivity ρRT along the c-axis and activation energy Ea rapidly decreased with increasing pressure. The temperature-dependent thermoelectric power S was that of a typical one-dimensional (1D) semiconductor. However the high absolute value of S suggested that this electronic system should be strongly correlated. Although the electrical resistivity exhibited monotonous temperature-dependence, the magnetic susceptibility clearly indicated a Peierls-type transition and marked fluctuation from RT. Both Peierls-type transitions and fluctuations are characteristic phenomena to 1D conductors. Furthermore ESR spectra manifested that the Peierls-type transition occurred at 100 K. The inconsistency between the electrical behavior (without a phase-transition) and magnetic behavior (with a phase-transition) indicates separation of the degrees of freedom in spin and charge (spin-charge separation) of this material. Spin-charge separation is a theoretically predicted phenomenon peculiar to the 1D conductors with strong correlation. The reflectance spectra were quantitatively explained by a 1D Hubbard model, and manifested the existence of a structural fluctuation of this material from RT. Based on these observed physical properties it is concluded that [Co(2,3-Nc)(CN)2]CH3CN is a strongly correlated 1D semiconductor with a Mott(Hubbard) type energy gap and characterised with a fluctuation and spin-charge separation.