Charge current polarization and magnetoresistance in ferromagnetic/organic semiconductor/ferromagnetic devices

Spin-polarized injection and transport in ferromagnetic/organic semiconductor/ferromagnetic devices are studied theoretically. Based on the spin diffusion theory and Ohm’s law, we obtain the charge current polarization and the magnetoresistance, which takes into account the special carriers in organic semiconductors. From the calculation, it is found that the charge current polarization decreases exponentially from the ferromagnetic layer into the organic layer and polarons are effective spin carriers in organic semiconductors for polarized charge current. To get an apparent magnetoresistance in an organic device, it is better to adopt a spin-dependent interface, and the thickness of the organic interlayer is much smaller than the spin diffusion length. Spin polarons are effective carriers for gaining remarkable magnetoresistance in ferromagnetic/organic semiconductor/ferromagnetic devices.