Effect of Co permeation on spin polarized transport in a Co/organic semiconductor (OSC) structure

Co atoms will permeate into the soft organic material to form a magnetic permeated sub-layer (MPS) during the fabrication of an organic spin device, such as Co/OSC/LSMO. We considered the OSC as a two-sublayer structure of MPS and pristine OSC, and then established a dynamic spin-diffusion equation to study the effect of MPS on the spin current polarization and the magnetoresistance of the device. It was found that the MPS will change the spin transport due to its different spin-flip time and mobility from that in the pristine OSC. The splitting of spin-flip times will be favorable to the spin polarization transport. Mobility of spin polarons in the MPS will be reduced due to the scattering of the Co atoms, which will weaken the spin polarization. For a given device, effect of the thickness of the MPS on the spin polarization is discussed. Finally, we calculated the magnetoresistance of a Co/OSC/LSMO device. A theoretical result which is consistent with the experimental data was obtained. (C) 2009 Elsevier B.V. All rights reserved.