Magnetoresistance Crossover in Cobalt/Poly(3-hexylthiophene,2,5-diyl) Hybrid Films Due to the Interface Effect

While organic electronic devices are multifunctional and offer high performance, they are nonetheless confronted with serious interface problems in their metal/organic-semiconductor contacts. In this work, a cobalt film is magnetron sputtered onto a P3HT film to simulate the Co/P3HT interface in a device. With decreasing Co thickness, the magnetoresistance is reversed from negative to positive, due to the increasing influence of the Co/P3HT interfacial layer. This result clearly shows the importance of the metal/organic interface in organic spin valves for spintronic applications.