Spin Polarization at Organic-Ferromagnetic Interface: Effect of Contact Configuration

Based on ab initio theory, the interfacial spin polarization of a benzene-dithiolate molecule vertically adsorbed on a nickel surface is investigated by adopting different microscopic contact configurations. The results demonstrate a strong dependence of the interfacial spin polarization on the contact configuration, where the sign of spin polarization may vary from positive to negative with the change of contact configuration. By analyzing the projected density of states, an interfacial orbital hybridization between the 3d orbital of the nickel atom and the spa hybridized orbital of the sulfur atom is observed. We also simulated the interfacial adsorption in mechanically controllable break junction experiments. The magnetoresistance obtained from Julliere model is about 27% based on the calculated interfacial spin polarization, which is consistent with experimental measurement.