Effects of structural relaxation on calculations of the interface and transport properties of Fe/MgO(001) tunnel junctions

Abstract

The relaxation of the interface structure of Fe/MgO(100) magnetic tunnel junctions predicted by density-functional theory depends significantly on the choice of exchange and correlation functional. Bader analysis reveals that structures obtained by relaxing the cell with the local spin-density approximation (LSDA) display a different charge transfer than those relaxed with the generalized gradient approximation (GGA). As a consequence, the electronic transport is found to be extremely sensitive to the interface structure. In particular, the conductance for the LSDA-relaxed geometry is about 1 order of magnitude smaller than that of the GGA-relaxed one. Surprisingly, the effect of the exchange and correlation potential within both the LSDA and the GGA has a little effect on the calculated transmission coefficient when applied to the same Fe/MgO/Fe (001) geometry. The high sensitivity of the electronic current to the details of the relaxed interface might explain the discrepancy between the experimental and calculated values of magnetoresistance.