Interface effects on tunneling magnetoresistance in organic spintronics with flexible amine–Au links

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 a 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 a fixed number of Au layers. Even as the Au thickness changes, the 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. (paper)