研究期間：10108~10207;The spin injection into ferromagnet(FM)/semiconductor(SC) and FM/SC/FM heterojunctions are rapidly growing fields, due to their potential applications in spintronics devices. Recently, the spin injection efficiency has been successfully improved via inserting a tunneling slab, which can be either Schottky barrier SC or insulators (I). In this project, we choose the wide band gap AlN as the central SC layer with polar (pAlN) and non-polar (npAlN) surfaces. In order to understand the effect of AlN surface polarity-induced interfacial charge accumulation on the spin transport properties, we’ll first generalize the first-principles spin-polarized pseudofunction (PSFS) method with the integrated piecewise thermal equilibrium approach, so the spin-polarized current densities and TMR can be obtained in both Fe/pAlN/Fe and Fe/npAlN/Fe junctions. Moreover, we’ll apply the tight-binding model with the non-equilibrium Keldysh Green’s formulism to predict the non-collinear spin-transfer torque, T||, effect in both cases. For Fe/npAlN/Fe junction, which can be treated as an ideal MTJ, my newly derived general expression shows that non-collinear T|| can be estimated directly from the spin current densities solely in parallel and anti-parallel configurations. While for Fe/pAlN/Fe junction, with opposite interfacial charge accumulations at Fe/Al and Fe/N interfaces, this case can be treated as a disordered MTJ with multi impurity potentials at two interfaces, corresponding to the interfacial energy states calculated from the first-principles PSFS method. Then, the non-equilibrium Keldysh Green’s function method with Dyson equation can be applied to derive a new general expression of T|| for pAlN case. We believe our theoretical results will give more physical insights of fundamental spin transport mechanisms and also will provide some guidelines for future SC-based sprintronics applications.
