Spin-dependent tunneling in epitaxial systems: Band dependence of conductance

We present first principles based calculations of the tunneling conductance between iron electrodes separated by semiconducting ZnSe. We assume that F e (100) and ZnSe (100) atomic planes are epitaxed. We find that the conduct ance depends strongly on the relative alignment of the magnetic moments in the two Fe electrodes. The relative change in conductance increases dramati cally as the thickness of the semiconductor increases. We show that this ef fect is due to the fact that electrons from a particular majority spin band are injected efficiently into the ZnSe from the Fe and also that electrons are ejected efficiently from the ZnSe into this band. Our calculations are based upon the Landauer-Buttiker expression for the conductance which is e xpressed in terms of the transmission matrix elements. (C) 1998 American In stitute of Physics. [S0021-8979(98)20311-2].