Resonant electronic states and I-V curves of Fe/MgO/Fe(100) tunnel junctions

TL;DR

This paper theoretically investigates the bias dependence of tunnel magnetoresistance in Fe/MgO/Fe junctions, revealing how resonant interface states and band-edge alignments influence I-V characteristics and TMR at different voltages.

Contribution

It introduces a self-consistent method combining non-equilibrium Green's functions with density functional theory to analyze TMR bias dependence in Fe/MgO/Fe junctions.

Findings

Resonant interface states dominate TMR at voltages below 20 mV.

Parallel configuration resonant transport is quenched at voltages comparable to interface state width.

At higher bias, TMR decreases due to band-edge alignment effects.

Abstract

The bias dependence of the tunnel magnetoresistance (TMR) of Fe/MgO/Fe tunnel junctions is investigated theoretically with a fully self-consistent scheme that combines the non-equilibrium Green's functions method with density functional theory. At voltages smaller than 20 mVolt the I-V characteristics and the TMR are dominated by resonant transport through narrow interface states in the minority spin-band. In the parallel configuration this contribution is quenched by a voltage comparable to the energy width of the interface state, whereas it persists at all voltages in the anti-parallel configuration. At higher bias the transport is mainly determined by the relative positions of the $\Delta_1$ band-edges in the two Fe electrodes, which causes a decrease of the TMR.