What determines the sign reversal of magnetoresistance in a molecular tunnel junction?
What determines the sign reversal of magnetoresistance in a molecular tunnel junction?
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DOI：
10.1021/nn3006569
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发表时间：
2012-03
期刊：
影响因子：
17.1
通讯作者：
S. Mandal;R. Pati
中科院分区：
文献类型：
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作者：
S. Mandal;R. Pati
有机自旋阀结构的隧穿磁电阻（TMR）正负符号现象一直困扰着有机自旋电子学的研究者。在这篇文章中，我们提供了一个答案，通过探索在一个单分子自旋阀结的TMR金属分子界面的作用。夹在两个镍电极之间的平面有机分子被用来建立一个典型的自旋阀结。一个无参数，单粒子绿色函数的方法结合后验，自旋不受限制的密度泛函理论，涉及一个混合轨道相关的功能是用来计算自旋极化电流。外偏置的影响被明确地包括在研究自旋阀的行为。我们的计算表明，只有一个小的变化，在金属分子结的界面距离可以改变的TMR的符号从一个正值到一个负值。通过改变3%的界面距离，参与本征通道的数量以及它们的轨道特性的反平行配置的变化，导致在TMR的符号反转。
The observations of both positive and negative signs in tunneling magnetoresistance (TMR) for the same organic spin-valve structure have baffled researchers working in organic spintronics. In this article, we provide an answer to this puzzle by exploring the role of metal-molecule interface on TMR in a single molecular spin-valve junction. A planar organic molecule sandwiched between two nickel electrodes is used to build a prototypical spin-valve junction. A parameter-free, single-particle Green's function approach in conjunction with a posteriori, spin-unrestricted density functional theory involving a hybrid orbital-dependent functional is used to calculate the spin-polarized current. The effect of external bias is explicitly included to investigate the spin-valve behavior. Our calculations show that only a small change in the interfacial distance at the metal-molecule junction can alter the sign of the TMR from a positive to a negative value. By changing the interfacial distance by 3%, the number of participating eigenchannels as well as their orbital characteristics changes for the antiparallel configuration, leading to the sign reversal in TMR.