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 Fe (100) and ZnSe (100) atomic planes are epitaxed. We find that the conductance depends strongly on the relative alignment of the magnetic moments in the two Fe electrodes. The relative change in conductance increases dramatically as the thickness of the semiconductor increases. We show that this effect 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 endash Buettiker expression for the conductance which is expressed in terms of the transmission matrix elements. copyright 1998 American Institute of Physics