Spin polarization of electrons tunneling through magnetic-barrier nanostructures

We present a theoretical investigation of the spin-dependent transport properties of electrons in nanostructures consisting of realistic magnetic barriers created by a lithographic patterning of ferromagnetic or superconducting films. It is shown that a significant electron-spin polarization effect can be induced by such magnetic-barrier nanostructures with a symmetric magnetic field. It is also shown that an applied bias voltage or an external magnetic field can greatly change the degree of the electron-spin polarization in magnetic-barrier nanostructures. When the applied bias voltage increases, the electron-spin polarization shifts toward the low-energy end and gradually decreases, while, with an increase of the external magnetic field, the electron-spin polarization shifts toward the high-energy direction and successively enlarges. It is also found that the degree of the electron-spin polarization can be tuned with the electric barrier induced by a constant voltage applied to the metallic stripe of system.