Ab initiocalculations of interface effects in tunnelling through MgO barriers on Fe(100)

Abstract

The tunnel-magneto-resistance (TMR) effect has been extensively studied in the last couple of years. While some experiments showed a strong dependence on the metal–insulator interface in these systems, most theoretical work gave little emphasis to the complicated interplay between electronic structure, atomic structure and the tunnelling process. We present calculations of the atomic structure of Fe/MgO/Fe(001) interfaces and its influence on the electronic structure. The tunnel current is calculated using the Landauer approach to describe the electron transport.

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

“…In particular, GGA returns a Fe-O distance of 2.22 Å in agreement with experiment 7,8 and the reduction in d −1 is less pronounced than that for the LSDA. Our GGArelaxed structure is in good agreement with other GGA studies 10,32 and rather close to the reference unrelaxed interface structure. Figure 1 demonstrates that the charge transfer between Fe and MgO is very sensitive to the interface structure.…”

Effect of interface states on spin-dependent tunneling inFe∕MgO∕Fetunnel junctions

“…Very large TMR values exceeding 200% were indeed measured for such junctions by Parkin et al [9] and Yuasa et al [10]. Recently, a more accurate calculation [11] based on the FLAPW method confirmed the conclusions of Refs. 6, 7.…”

“…This feature makes any calculation of the interface states in Fe/MgO/Fe unreliable in terms of their Fermi level intercepts: The LDA itself does not provide 0.01 eV accuracy. It is very likely that this particular feature of the interface states is the reason why earlier calculations based on different methods [6,7,11] result in very dissimilar shapes of the minorityspin conductance plotted as a function of k . Fig.…”

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

“…All results reported here adopt a generalized linear muffin-tin orbitals (LMTO) method 20,21 , and use the relaxed nuclear coordinates of the Fe/MgO interface from Ref. 24 . Minority DOS of the Fe/MgO superlattice, projected on the Fe interfacial atom, and onto the oxygen atom in the second layer from the interface, are depicted in Fig.…”