Magnetoresistance effect in an organic spin valve

Abstract

Based on the spin diffusion theory and the Ohm’s law, we theoretically studied the magnetoresistance (MR) effect in an organic spin valve with structure of ferromagnetic/organic semiconductor/ferromagnetic system, which takes into account the special characteristics of organic semiconductors. Self-trapped states, such as spin polarons as well as spinless bipolarons are assumed to be the main carriers in organic semiconductors. From the calculation, it is found that MR ratio increases with the increasing of the polaron proportion and rapidly decreases with the increasing of the organic layer thickness. MR ratio can be enhanced remarkably when the interfacial resistances are spin related. Effects of the conductivity match and the spin polarization of the ferromagnetic layer on the MR are also discussed.