Quasi-ferromagnet spintronics in the graphene nanodisc-lead system
Quasi-ferromagnet spintronics in the graphene nanodisc-lead system
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DOI：
10.1088/1367-2630/11/9/095005
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发表时间：
2009-09-30
影响因子：
3.3
通讯作者：
Ezawa, Motohiko
中科院分区：
文献类型：
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作者：
Ezawa, Motohiko
锯齿形石墨烯纳米盘可以被解释为具有内部自由度的量子点。这是很好地描述了无限程海森堡模型。我们研究了它的结晶特性。在准铁磁态和准顺磁态之间存在准相变，其信号是比热和磁化率的尖峰。我们还分析了当两个引线连接到纳米盘上时，晶体特性是如何受到影响的。结果表明，铅效应描述的多自旋近藤哈密顿量。比热出现新的峰值，基态多重数变为无铅体系的一半。另一个铅效应是增强铁磁有序性。作为铁磁体，纳米盘可以用作自旋过滤器。此外，由于弛豫时间是有限的，因此可以通过施加外部自旋电流来控制纳米盘的自旋。然后，我们提出了各种各样的纳米盘和铅制成的自旋电子器件：自旋存储器，自旋放大器，自旋阀，自旋场效应晶体管，自旋二极管和自旋逻辑门，如自旋XNOR门和自旋XOR门。石墨烯纳米盘很可能是未来纳米电子和自旋电子器件的基本组成部分。
A zigzag graphene nanodisc can be interpreted as a quantum dot with an internal degree of freedom. It is well described by the infinite-range Heisenberg model. We have investigated its thermodynamical properties. There exists a quasi-phase transition between the quasi-ferromagnet and quasi-paramagnet states, as signaled by a sharp peak in the specific heat and in the susceptibility. We have also analyzed how thermodynamical properties are affected when two leads are attached to the nanodisc. It is shown that lead effects are described by the many-spin Kondo Hamiltonian. There appears a new peak in the specific heat, and the multiplicity of the ground state becomes just one half of the system without leads. Another lead effect is to enhance ferromagnetic order. Being a ferromagnet, a nanodisc can be used as a spin filter. Furthermore, since the relaxation time is finite, it is possible to control the spin of the nanodisc by applying an external spin current. We then propose a rich variety of spintronic devices made of nanodiscs and leads: spin memory, spin amplifier, spin valve, spin-field-effect transistor, spin diode and spin logic gates such as spin-XNOR gate and spin-XOR gate. Graphene nanodiscs could well be basic components of future nanoelectronic and spintronic devices.