Magnetoresistance modulation due to interfacial conductance of current perpendicular-to-plane spin valves

Abstract

We study the effects of the interfacial conductivity σi and spin asymmetry γ at the boundaries between the ferromagnetic (FM) and nonmagnetic layers of a current perpendicular-to-plane spin-valve trilayer, based on the semi-classical drift-diffusion model. We found that the expected increase in the MR ratio with decreasing σi occurs only for moderately low σi and γ larger than some critical value γc. For γ < γc, the competitive contribution to spin-dependent scattering in the FM layers leads to a reduction in MR with decreasing σi. For even lower σi values, our calculations predict a stronger suppression of MR, which applies even when γ exceeds γc. We attribute this MR suppression to the spin relaxation within the FM layers, since the effect disappears in the limit of infinite spin-relaxation length. Thus, for highly spin-asymmetric interfacial resistances (with γ > γc), there is an optimal conductivity σi which yields the maximum MR ratio. © 2006 Elsevier B.V. All rights reserved.