A Way To Measure Electron Spin-Flipping At Ferromagnetic/Nonmagnetic Interfaces And Application To Co/Cu

We describe a technique, using the current-perpendicular-to-plane (CPP) geometry, to measure the parameter delta(F/N), characterizing flipping of electron spins at a ferromagnetic (F)/nonmagnetic (N) metallic interface. The technique involves measuring the CPP magnetoresistance of a sample containing a ferromagnetically coupled [F/N](n) multilayer embedded within the 20 nm thick central Cu layer of a symmetric Py-based, double exchange-biased spin-valve. To focus on delta(F/N), the F- and N-layers are made thin compared to their spin-diffusion lengths. We test the technique using F/N=Co/Cu. Analyzing with no adjustable parameters, gives inconsistency with delta(Co/Cu)=0, but consistency with our prior value of delta(Co/Cu)=0.25 +/- 0.1. Taking delta(Co/Cu) as adjustable gives delta(Co/Cu)=0.33(-0.08)(+0.03).