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/MgO͑100͒ magnetic tunnel junctions predicted by densityfunctional 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 ͑LSDA͒ display a different charge transfer than those relaxed with the generalized gradient approximation ͑GGA͒. 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 GGArelaxed 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 ͑001͒ 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.

Effect of correlations on electronic structure and transport across (001) Fe/MgO/Fe junctions

“…The LSDA puts one peak just at E F , in agreement with several prior LSDA calculations [13][14][15][16][17] ). There is a corresponding IRS resonance in QSGW and G 0 W 0 , but it falls at E F +0.12 eV and E F +0.15 eV correspondingly.…”

“…At a fundamental level, the (001) Fe/MgO/Fe system presents an excellent opportunity to investigate the role of the interface and test our ability to predict critical properties controlling transport in a heterostructure with well defined interfaces 9 . The local spin density approximation (LSDA) has been used to predict TMR in Fe/MgO/Fe system [13][14][15][16][17] . Reports are largely in agreement with each other but at variance with differential conductance measurements for thin MTJs 12,18 .…”

A first-principles study of helium storage in oxides and at oxide–iron interfaces

“…Incidentally Fe-MgO interfaces have recently attracted a lot of attention since they exhibit a strong transverse magnetic resistance effect. [41][42][43][44][45] In the present work both Fe|MgO and Fe|FeO|MgO interface models were included, the geometries of which are illustrated in Fig. 8.…”

Strength of the symmetry spin-filtering effect in magnetic tunnel junctions

“…The fast increase of the TMR predicted numerically [1,5] for Fe/MgO/Fe MTJ is generally explained by the contribution to the transmission function in the APC from the interface resonance states (IRS) that exist in the minority Fe channel in a very narrow energy window near the Fermi energy [1,5,[7][8][9][10]. The IRS contribution to the APC transmission is significant at small N but decays fast when N increases that leads to superlinear TMR behavior at small N < 10.…”