Geometrical and Compositional Structure at Metal-Oxide Interfaces: MgO on Fe(001)

Abstract

The geometric structure of MgO deposited on Fe(001) in ultrahigh vacuum by electron evaporation was determined in detail by using surface x-ray diffraction. In contrast to the common belief that MgO grows in direct contact on the Fe(001) substrate, we find an FeO interface layer between the substrate and the growing MgO structure which has not been considered thus far. This result opens new perspectives for the understanding of the Fe/MgO/Fe(001) interface and the tunneling magnetoresistance effect in general.

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

“…Interestingly, the GGA results are significantly different from the LSDA ones. 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.…”

“…This is significantly different from 2.16 Å of the GGA-unrelaxed structure. The only available experimental results are for MgO on top of the Fe surface and Fe/MgO/Fe ͑001͒ with the presence of FeO at the interface, 7,8 where the FeO/MgO distance at the interface is about 2.20 Å. The LSDA relaxation also predicts that the spacing, d −1 , between the first two Fe layers next to the Fe/MgO interface is drastically reduced to 19% of that of bulk Fe.…”

“…In addition, in typical growth conditions the Fe layers close to the interface might be partially oxidized. [6][7][8] Many theoretical results have been published concerning the influence of interfacial structure on the electronic transport properties, 9-12 but little effort was devoted to the effect of the atomic relaxation and electron-electron correlation on the tunneling magnetoresistance. Notice, however, that in the literature whether or not the Fe/MgO interface is oxidized is controversial.…”

Tunneling magnetoresistance from a symmetry filtering effect

“…It was necessary, for example, to prevent oxidation of the Fe layer at the Fe-MgO interface [26], the reason for this is that O atoms in the interfacial Fe layer significantly degrade the overlap between the 1 states at the Fermi energy in Fe and in the MgO. In the perfect structure, the Fe electrode terminates in a square lattice of Fe atoms, immediately above each of these Fe atoms will be an O atom in the first atomic layer of MgO.…”

Minimization of interface roughness in laser deposited Fe/MgO multilayers

“…In Fig. 1 [10,11], due to a good lattice match (only On the same multilayer texture measurements were performed (see Fig. 2).…”