Study On Spin Transport Properties In Some Of Mesoscopic System

In this paper we theoretically investigate the electronic transport phenomena in the ferromagnetic/nonferromagnetic/ferromagnetic three-terminal heterojunction,ferromagnetic/nonferromagnetic/ferromagnetic with tunnel barrier, and the quantum ring with multiple arms structure, which possess great potential in future applications. We expect to provide theoretical foundation for the development of novel quantum devices with our work. The main results obtained in this paper are listed below:(l)We study theoretically the transmission coefficients and the spin-tunneling time in ferromagnetic/semiconductor/ferromagnetic three-terminal heterojunction in the presence of Rashba spin-orbit interaction. One-dimensional quantum waveguide theory is developed and applied to the three-terminal heterojunction in the presence of Rashba spin-orbit coupling. At the same time, based on the group velocity concept and the particle current conservation principle, we calculate spin-tunneling time as the function of the intensity of Rashba spin-orbit coupling and the length of the semiconductor. We find that as the length of the semiconductor increases, the spin-tunneling time does not increase linearly but shows slight behavior of oscillation. With the increasing of the spin-orbit coupling, the spin-tunneling time increases.(2)The electronic transport properties are studied theoretically in a ferromagnetic/semiconductor/ ferromagnetic heterojunction with a tunnel barrier. The Rashba spin-orbit interaction in the semiconductor and the significant quantum size are taken into account simultaneously. It is found that the tunnel barrier plays a decisive role in the transmission coefficients of spin-up and spin-down electrons. On the basis of the group...