What Determines the Sign Reversal of Magnetoresistance in a Molecular Tunnel Junction?
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- 作者：Subhasish Mandal ; Ranjit Pati
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：April 24, 2012
- 年：2012
- 卷：6
- 期：4
- 页码：3580-3588
- 全文大小：531K
- 年卷期：v.6,no.4(April 24, 2012)
- ISSN：1936-086X
文摘
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鈥搈olecule 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鈥檚 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鈥搈olecule 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.