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arXiv 0910.4415cond-mat.mes-hall
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磁性隧道结中Al终端对自旋输运的界面效应

Interfacial Effects of Al-Termination on Spin Transport in Magnetic Tunnel Junctions

T. Tzen Ong, A. M. Black-Schaffer, W. Shen, B. A. Jones

摘要:

实验表明,Co/Al $_2$ O $_3$磁性隧道结(MTJ)中的隧道电流是正自旋极化的,这与标准隧道理论直观地预期的相反,标准隧道理论给出的自旋极化完全取决于Co层的$E_F$处的态密度(DOS)。在这里,我们报告的理论结果,给出一个积极的隧道自旋极化和隧道磁电阻(TMR)是在良好的协议与实验。从密度泛函理论(DFT)的计算,富铝界面MTJ与原子级的障碍被证明有一个积极的极化DOS界面附近。我们还提供了一个原子模型的计算,它给出了见解的正极化的来源。一个层和自旋相关的有效质量模型,使用从DFT结果提取的值,然后被用来计算隧道电流,这表明积极的自旋极化。最后,我们从隧穿自旋极化率计算了TMR,与实验结果符合得很好。

英文摘要:

Experiments have shown that the tunneling current in a Co/Al$_2$O$_3$ magnetic tunneling junction (MTJ) is positively spin polarized, opposite to what is intuitively expected from standard tunneling theory which gives the spin polarization as exclusively dependent on the density of states (DOS) at $E_F$ of the Co layers. Here we report theoretical results that give a positive tunneling spin polarization and tunneling magnetoresistance (TMR) that is in good agreement with experiments. From density functional theory (DFT) calculations, an Al-rich interface MTJ with atomic-level disorder is shown to have a positively polarized DOS near the interface. We also provide an atomic model calculation which gives insights into the source of the positive polarization. A layer and spin dependent effective mass model, using values extracted from the DFT results, is then used to calculate the tunneling current, which shows positive spin polarization. Finally, we calculate the TMR from the tunneling spin polarization which shows good agreement with experiments.

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