Electronic structure and spin-dependent tunneling conductance under a finite bias

Abstract

We present a spin-polarized self-consistent density functional theory (DFT) method for calculation of the electronic structure and transport properties of a system under a finite bias voltage. This method is implemented within the layer Korringa-Kohn-Rostoker approach. We calculate the tunneling conductance and the magnetoresistance (MR) of Fe/FeO/MgO/Fe tunneling junctions as functions of bias voltage. We find that the change in the electronic structure is minimal as a function of bias. The effective capacitance is consistent with the dielectric constant of MgO. The tunneling conductance is highly nonlinear. At low biases the TMR ratio is greatly reduced due to the large contribution to the tunneling current from interface resonance states. This contribution diminishes as the bias voltage increases, leading to an increase of the TMR ratio as a function of bias.