Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier

Abstract

We use uncoupled Co/Cu/Co and Co/Cu/Co/Cu spin-valve structures with a Ru barrier shifted through the top Co and Cu layer, respectively, to measure the longest of the electron mean free paths in Co and Cu as originally suggested by Parkin. From semiclassical transport calculations and careful analysis of the magnetoresistance data we conclude that the exponential behavior of ΔG is uniquely related to the longest of the Co and Cu mean free paths under the condition of effective spin-dependent filtering at the interfaces or in the bulk of the Co. In this regime we have compared ${\lambda }^{\mathrm{long}}$ in Co and Cu with bulk conductivities (∝${\lambda }^{\mathrm{short}}$+${\lambda }^{\mathrm{long}}$), yielding no strong evidence for bulk spin-dependent scattering in Co. © 1996 The American Physical Society.