  Organic spintronics is a promising emerging field, but the sign of the
tunneling magnetoresistance (TMR) is highly sensitive to interface effects, a
crucial hindrance to applications. A key breakthrough in molecular electronics
was the discovery of amine-Au link groups that give reproducible conductance.
Using first principles calculations, we predict that amine-Au links give
improved reproducibility in organic spintronics junctions with Au-covered Fe
leads. The Au layers allow only states with sp character to tunnel into the
molecule, and the flexibility of amine-Au links results in a narrow range of
TMR for fixed number of Au layers. Even as the Au thickness changes, TMR
remains positive as long as the number of Au layers is the same on both sides
of the junction. Since the number of Au layers on Fe surfaces or Fe
nanoparticles can now be experimentally controlled, amine-Au links provide a
route towards robust TMR in organic spintronics.

Materials Science;Mesoscale and Nanoscale Physics