Influence of the interface structure on the bias dependence of tunneling magnetoresistance

Ab initio calculations for the tunneling magnetoresistance (TMR) in planar Fe∕MgO∕Fe junctions are presented. The electronic and magnetic structure of the junctions are calculated self-consistently in the framework of density functional theory. The bias dependence of the tunneling conductance and the magnetoresistance is calculated in the limit of coherent tunneling. Positive and negative TMR ratios are obtained as a function of interface structure and even a sign reversal of TMR as a function of bias was found in agreement with experiments.