| Summary: | 碩士 === 國立中央大學 === 物理學系 === 102 === The manipulation of spin transport properties in FM/single molecule/FM junctions has attracted intensive attentions due to their potential applications in molecular spin electronics, where FM denotes the ferromagnetic materials. In this study, we employ the first-principles calculation with the Keldysh Green’s function method [8] to calculate the spin transport properties of the σ-saturated Co/Alkanedithiols(ADT)/Co and the π-saturated Co/Benzenedithiol(BDT)/Co single molecular junctions. In order to simulate the single molecular magnetic junction in realistic experimental system [5], we stretch the junction by increasing the distance between two Co electrodes in small steps, optimize again, and continued to do so, until the junction is broken down. The calculated total energy, bond lengths, and bond angles conclude that the central molecule indeed plays an important role on the stretching process and the breakdown situation. Once we obtain the relaxed junction geometry under stretching process, we employ the DFT+NEGF+LDA calculation to calculate the spin-polarized transmission spectra and PDOS’s for both PC and APC situations. For both junctions, the dramatic variation from the highly spin-polarized transmission in PC to the non-spin-polarized transmission in APC indicates the possibility for the high MR value under bias. However, the more conductive BDT molecule enhances the spin transport probabilities near EF may be a promising candidate for the molecular spintronics application.
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