Application of regioregular polythiophene in spintronic devices:Effect of interface

The authors report on fabrication and characterization of a polymeric spin valve with the conjugated polymer regioregular (poly 3-hexylthiophene) (RRP3HT) as the spacer layer. The device structure is La 0.67 Sr 0.33 Mn O 3 (LSMO)/polymer/Co, with half-metallic, spin-polarized LSMO acting as the spin-injecting electrode. The spin valve shows behavior similar to a magnetic tunnel junction though the nonmagnetic spacer layer ( ∼ 100 nm ) is much thicker than the tunneling limit. They attribute this behavior to the formation of a thin spin-selective tunneling interface between LSMO and RRP3HT caused by RRP3HT, chemically attaching to LSMO as observed by x-ray photoelectron spectroscopy measurement. This gives rise to ∼ 80 % magnetoresistance (MR) at 5 K and ∼ 1.5 % MR at room temperature. They found that by introducing monolayer of different organic insulators between LSMO and RRP3HT the spin-selective interface is destroyed and the spin injection is reduced. Their results show that organic materials are promising candidates for spintronic applications.