Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284, USA.
J Chem Phys. 2013 Aug 14;139(6):064306. doi: 10.1063/1.4817335.
Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and current polarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8-FeMg8 focus on the effect of electrode contact distance and the support. The calculated I-V curves show negative differential resistance behavior at larger electrode-cluster contact distances. Further, the equilibrium conductance in ferromagnetic state shows an unusually high spin polarization that is about 81.48% for specific contact distance, and a large magnetoresistance ratio exceeding 500% is also found. The results show that the superatom assemblies can provide unusual transport characteristics, and that the spin polarization and magnetoresistance can be controlled via the contact geometry.
使用密度泛函理论结合凯莱-德舍非平衡格林函数方法研究了 FeMg8 磁性超原子及其二聚体的电子输运。对于单个团簇，我们研究了在 Au(100)表面以各种取向支撑的团簇，结果表明输运对接触几何形状敏感。对于 Mg 正方形反棱柱体的轴与输运方向成 45°、垂直和平行的情况进行的研究表明，平衡电导、转移电荷和电流各向异性都可以随取向显著变化。我们对 FeMg8-FeMg8 磁性超原子二聚体的输运研究侧重于电极接触距离和支撑的影响。计算出的 I-V 曲线在较大的电极-团簇接触距离下显示出负微分电阻行为。此外，铁磁态下的平衡电导显示出异常高的自旋极化，对于特定的接触距离约为 81.48%，还发现了超过 500%的大磁电阻比。结果表明，超原子组装可以提供异常的输运特性，并且通过接触几何形状可以控制自旋极化和磁电阻。
