Effect of electron localization on the edge-state spins in a disordered network of nanographene sheets
Effect of electron localization on the edge-state spins in a disordered network of nanographene sheets
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DOI：
10.1103/physrevb.81.115408
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发表时间：
2010-03-01
影响因子：
3.7
通讯作者：
Tanaka, Hidekazu
中科院分区：
文献类型：
--
作者：
Joly, V. L. Joseph;Takahara, Katsunori;Tanaka, Hidekazu
研究了三维随机网络结构纳米石墨烯片的边态自旋的磁性及其动力学行为，研究了电子局域化效应对磁性的影响.电子输运由纳米石墨烯片之间的库仑能隙可变范围跳跃控制。在高温下，具有均匀自旋系统特征的电子自旋共振（ESR）信号揭示了给定纳米石墨烯片中边态自旋和导电π电子的强耦合系统的自旋弛豫到晶格的瓶颈效应。在20 K以下，伴随着烧孔的不连续ESR谱线加宽证明了非均匀自旋态的形成，表明共振场的静态空间分布。这种不均匀性源于各个纳米石墨烯片上的亚铁磁矩的强度的分布，考虑到其形状随机变化的组成纳米石墨烯片具有不同的亚铁磁矩强度。强电子局域化低于20 K的internanographene电子跳跃是负责交叉从均匀的自旋状态的非均匀的，在后者的亚铁磁短程有序是明显的边缘状态的自旋系统。
The magnetism and its dynamical behavior is investigated in relation to electron-localization effect for the edge-state spins of three-dimensional randomly networked nanographene sheets which interact weakly with each other. The electron transport is governed by Coulomb-gap variable-range hopping between nanographene sheets. At high temperatures, the electron spin resonance (ESR) signal with a feature of homogeneous spin system reveals the bottleneck effect in the spin relaxation to the lattice for a strongly coupled system of edge-state spins and conduction pi electrons, in a given nanographene sheet. Below 20 K, a discontinuous ESR line broadening accompanied by hole-burning proves the formation of an inhomogeneous spin state, indicating a static spatial distribution of on-resonance fields. This inhomogeneity originates from a distribution of the strengths of the ferrimagnetic moments on the individual nanographene sheets, taking into account that the constituent nanographene sheets with their shapes randomly varying have different strengths of ferrimagnetic moments. Strong electron localization below 20 K in the internanographene electron hopping is responsible for the crossover from the homogeneous spin state to the inhomogeneous one, in the latter of which ferrimagnetic short-range ordering is evident in the edge-state spin system.