Spin filtering and spin-polarization reversal in multilayered ferromagnetic metal/semiconductor heterostructures

We investigate spin-filtering effect in multilayered ferromagnetic (F)/semiconductor (S) heterostructures within the Landauer framework of ballistic transport. Spin-dependent transmission and polarization are calculated and analyzed for different magnetizations of three ferromagnetic layers in a F/S/F/F structure proposed in this work. The results indicate that in such a multilayered configuration and when the magnetizations of the middle and the right ferromagnetic layers are antiparallel, the transmission for spin-up and spin-down electrons can be separated, which is quite different from the transport properties in the F/S/F structure, where electrons of different spin orientations have exactly the same contributions to transmission if the magnetic moments of the two ferromagnetic layers are antiparallel. It is also shown that the F/S/F/F structure can have big values of the polarization than the F/S/F structure. The quantum size effect of the length of the middle ferromagnetic layer and that of the semiconductor layer are discussed. Moreover, the polarization can be reversed when we switch the magnetizations of the middle and the right ferromagnetic layers. (c) 2005 American Institute of Physics.