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Study of the π-d system involving phthalocyanine conductors

酞菁导体π-d体系的研究

基本信息

批准号：
09440244
负责人：
YAKUSHI Kyuya
金额：
$ 8.32万
依托单位：
Institute for Molecular Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 2000
项目状态：
已结题

项目摘要

Organic dilute magnetic alloy Co_<0.01>Ni_<0.99>Pc(AsF_6)_<0.5> involves localized spins on Co sites and itinerant π electrons along the one-dimensional Pc chain. From the angular dependence of the ESR properties, we identified that CoPc is relevantly substituted in this alloy. Based on the analysis of the anisotropic hyperfine structure, we determined the atomic orbital as 3d_<Z^2>, in which an unpaired electron is occupied. Analyzing the temperature dependence of g value and linewidth, we succeed to determine the π-d exchange energy between the localized spin on Co and itinerant electrons on Pc chain as |J_<πd>|=0.013 eV.The density of state at the Fermi level is determined as D_F=3.5 eV^<-1> per a spin through the analysis of the temperature dependence of the g value. Using these parameters, we estimate the Kondo temperature as T_K=2×10^<-5> K.The small value of the exchange energy comes from the characteristic electronic structure and molecular arrangement. HOMO and 3d_<Z^2> orbita … More l are separately distributed from each other in the CoPc molecule, which causes the small intra-molecular exchange energy. The phthalocyanine molecules are stacked in a fashion of metal-over-metal overlap. This overlap makes the overlap integral between HOMO and 3d_<Z^2> of adjacent molecule negligibly small, and thus causes the small inter-molecular exchange energy.θ-(BDT-TTP)_2Cu(NCS)_2 is regarded as a quasi-two-dimensional conductor according to the band calculation. This compound shows a second-order phase transition in resistivity around 250 K.Below the phase transition temperature, we found a drastic change in optical conductivity spectrum, in which the lowest electronic transition shifted to high-energy side opening a wide gap. The temperature and excitation light dependence of polaized Raman spectrum indicated that a charge disproportionation such as 2B^<+0.5>→B^0+B^<+1> occurred below the phase transition temperature. The magnetic susceptibility and ESR experiment suggest that the separated charge is vertically ordered along the molecular stack. Less

有机稀磁合金Co_&lt；0.01&gt；Ni_&lt；0.99&gt；Pc(AsF_6)_&lt；0.5&gt；包括Co位上的局域自旋和一维Pc链上巡回的π电子。从ESR性质的角度依赖关系可以看出，CoPc在该合金中得到了相应的取代。基于对各向异性超精细结构的分析，我们确定了原子轨道为3d_&lt；Z^2&gt；其中占据了一个未配对的电子。通过对g值和线宽的温度依赖关系的分析，我们成功地确定了定域自旋Co与Pc链上巡回电子之间的π-d交换能为|J_&lt；πd&gt；|=0.013 eV。通过对g值的温度依赖关系的分析，确定了费米能级的态密度为D_F=3.5 eV^&lt；-1&gt；。利用这些参数，我们估算出Kondo温度为T_K=2×10^&lt；-5&gt；K。交换能的小值来自于其特有的电子结构和分子排列。HOMO和3D_&lt；Z^2&>轨道…较多的L分散分布在CoPc分子中，导致分子内交换能较小。酞菁分子以金属对金属重叠的方式堆积在一起。这种重叠使得HOMO和相邻分子的3d_t；Z^2&gt；之间的重叠积分可以忽略不计，从而导致分子间交换能很小。根据能带计算，θ-(bdt-ttp)_2Cu(Ncs)_2被认为是准二维导体。该化合物的电阻率在250K附近呈现二级相变。在相变温度以下，我们发现光学电导谱发生了剧烈的变化，最低的电子跃迁向高能侧移动，打开了一条很大的空隙。偏振拉曼光谱的温度和激发光依赖关系表明，在相变温度以下发生了如2B^&lt；+0.5gt；→B^0+B^&lt；+1&gt；的电荷歧化。磁化率和ESR实验表明，分离的电荷沿分子堆栈垂直排列。较少