摘要:
石墨烯在未来纳米电子器件领域具有广泛的应用前景，但是基于扶手椅型石墨烯纳米带(AGNR)的磁输运性质的研究还比较少。本文理论上提出AGNR边缘桥接过渡金属Mn原子，再用双F 原子(或双H原子)饱和形成特殊化学修饰的纳米带(AGNR-Mn-F2或AGNR-Mn-H2)，并运用基于第一性原理和非平衡态格林函数相结合的方法对其磁输运性质进行理论计算。结果表明：这两种纳米带所构成的异质结(F2-AGNR-Mn-H2)具有优良的磁器件特性，即在很宽的偏压范围内，能实现100%的自旋极化，且在P(在左右电极垂直加上相同方向的磁场)和AP构型(在左右电极垂直加上相反方向的磁场)时，分别具有单自旋和双自旋过滤效应；同时发现，这种异质结也具有双自旋二极管效应，它的最大整流比可达到108。此外，改变开关磁场的方向，即从一种磁构型变换为另一种磁构型时，能产生明显的自旋阀效应，其巨磁阻高达108%。这意味着这种特殊的异质结能同时实现优良的自旋过滤、双自旋二极管及巨磁阻效应，这对于发展自旋磁器件有重要意义。
Abstract:
Graphene is predicted to hold a promising use for developing future miniaturized electronic devices. However, the magnetic transport properties based on the armchair-edged graphene nanoribbons (AGNRs) is less studied in currently existing work. So in this work the special chemical modified nanoribbons based on the edge of the AGNR bridged by the transition metal Mn atom and passivated subsequently by two F atoms or two H atoms (AGNR-Mn-F2 or AGNR-Mn-H2) are proposed theoretically. Our calculations from first-principle method based on the spin-polarized density functional theory combined with the non-equilibrium Green’s function technique show that the heterojunction F2-AGNR-Mn-H2 consisting of such two types of nanoribbons possesses the excellent magnetic device features, namely, the spin polarization is able to reach almost 100% in a very large bias region, and under P magnetic configuration (the external magnetic fields applied perpendicularly to two electrodes are set to point to the same direction), the single spin filtering effects can be realized, while under the AP configuration (the external magnetic fields applied perpendicularly to two electrodes are set to point to the opposite directions), the dual spin filtering effects can be realized. It is also found that such a heterojunction features dual diode-like effect, and its rectification ratio is up to be 108. Additionally, changing the direction of switching magnetic field, namely, changing the magnetic configurations from one kind of case to another, would lead to an obvious spin valve effect, and the giant magnetoresistace approaches to 108%. These findings suggest that the excellent spin polarization, dual diode-like effect, and giant magnetoresistace effect can be realized simultaneously for this heterojunction, therefore, it holds good promise in developing spintronic devices.
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