Spin-polarized transport through a magnetic heterostructure: tunneling and spin filtering effect

We present tight-binding Green's function investigations on spin-polarized transport through a magnetic heterostructure system, which is made of two superlatticed magnetic layers separated by a nonmagnetic low-density-carrier spacer. The results confirm that in such a system, tunneling is one of the key mechanisms in electron transport. When tunneling effect is taken into account, the magnetoresistance ratios are reduced significantly. We also study the influence of the applied bias on the spin filtering effect. It is found that the current density is almost completely spin-polarized in a wide range of the applied bias, which indicates the heterostructure system can act as a good spin filter. (C) 2002 Elsevier Science B.V. All rights reserved.