Influence of electrode structure on magnetotransport in magnetic tunnel junctions

The physical structure of the magnetic electrodes of Co-[Al.sub.2][O.sub.3]-Co magnetic tunnel junctions has been investigated by means of [sup.59]Co nuclear magnetic resonance and X-ray diffraction. Junctions sputtered on FeMn have an essentially fcc (111)-oriented bottom electrode, while all top electrodes and the bottom electrodes of junctions sputtered on Ta are polyphase and polycrystalline. The specifics of the electronic structure of the electrode crystal phases can explain the extra features and asymmetry in the conductance-versus-bias behavior observed in FeMn-based junctions. Index Terms--Electronic structure, magnetic tunnel junctions, NMR, structural analysis.