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arXiv 0710.0957cond-mat.mtrl-sci
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一种室温铁磁半导体缺陷石墨烯相的预测

A Defective Graphene Phase Predicted to be a Room Temperature Ferromagnetic Semiconductor

L. Pisani, B. Montanari, N. M. Harrison

摘要:

理论计算,基于混合交换密度泛函理论,被用来表明,在石墨烯的周期性阵列的缺陷产生铁磁基态在室温下意外大的缺陷分离。这是证明的缺陷,包括一个碳空位,其中两个悬挂键饱和与H原子。的磁耦合机制进行了分析,发现是由于在$π$电子系统相对于一个远程自旋极化的不稳定性,其特征在于在相邻的碳原子之间的自旋方向交替。$π$键的破坏在费米边缘打开了一个半导体间隙。能隙的大小和磁耦合强度是缺陷分离的强函数,因此可以通过改变缺陷浓度来控制。半导体的能隙和电子有效质量的位置是强烈的自旋依赖性,这是预期的结果在自旋不对称的输运性质的系统。因此,有缺陷的石墨烯片是一种非常有前途的材料,具有用于定制未来自旋电子器件特性的内置机制。

英文摘要:

Theoretical calculations, based on hybrid exchange density functional theory, are used to show that in graphene a periodic array of defects generates a ferromagnetic ground state at room temperature for unexpectedly large defect separations. This is demonstrated for defects that consist of a carbon vacancy in which two of the dangling bonds are saturated with H atoms. The magnetic coupling mechanism is analysed and found to be due to an instability in the $π$ electron system with respect to a long-range spin polarisation characterised by alternation in the spin direction between adjacent carbon atoms. The disruption of the $π$-bonding opens a semiconducting gap at the Fermi edge. The size of the energy gap and the magnetic coupling strength are strong functions of the defect separation and can thus be controlled by varying the defect concentration. The position of the semiconducting energy gap and the electron effective mass are strongly spin-dependent and this is expected to result in a spin asymmetry in the transport properties of the system. A defective graphene sheet is therefore a very promising material with an in-built mechanism for tailoring the properties of the spintronic devices of the future.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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