Influence of spin relaxation on magnetoresistance

Abstract

We represent the spin-dependent transport across a pseudospin-valve structure as described by the spin drift-diffusion (SDD) theory by an effective two-current model, in which the spin relaxation effects are globally absorbed into the two effective branch resistances. Our approach has eliminated the need for "spin flip" resistances interconnecting the two spin branches, which have the disadvantage of artificially localizing the effects of spin relaxation to arbitrary spatial points. We confirm the accuracy of our effective two-current model with the full numerical SDD solution. Based on our model, we found that (i) the overall magnetoresistance (MR) is much more sensitive to the spin relaxation effect in the nonmagnetic (NM) layer, compared to that in the ferromagnetic (FM) layers, and that (ii) the effective spin relaxation length λE in the NM layer is intrinsically linked to the conductivity N,F of the NM and FM layers. We found that λE = λN ()12, where λN is the nominal spin relaxation length in the NM layer and = (N F). The analytical link between spin relaxation and conductivity explains the previously described anomalous suppression of MR, when the conductivity ratio exceeds a certain critical value C. © 2007 American Institute of Physics.