Measurement of resistance and spin-memory loss (spin relaxation) at interfaces using sputtered current perpendicular-to-plane exchange-biased spin valves

We describe measurements using a technique for determining inter facial res istances and loss of spin-direction memory (spin relaxation) for nonmagneti c metals and nonmagnetic interfaces. The technique involves inserting the m etal of interest, or a multilayer, into the middle of a current-perpendicul ar (CPP) permalloy-based exchange-biased spin-valve and monitoring the resu lting increase in CPP resistance and decrease in magnetoresistance. The tec hnique has the advantage over earlier ones of giving both uniform current a nd control of the required magnetic states. We test and validate the techni que using (a) an alloy, CuPt (6 at. %). in which the spin-diffusion length has previously been measured with a different technique, (b) a metal, Ag, w here we expect a long spin-diffusion length, and (c) Cu/Ag interfaces, wher e we expect little if any spin-memory loss. We then use the technique to me asure spin-memory-loss (thr spin-diffusion length) at 4.2 K of the antiferr omagnetic alloy FeMn, which is used for pinning the ferromagnetic layers in our spin-valves, and of sputtered single layers of V, Nb, and W preparator y to measuring interfacial resistance and intel facial spin-memory loss in sputtered [Cu/Ag](N), [Cu/V](N), [Cu/Nb](N). and [Cu/W](N) multilayers with N repeats. To our surprise, we discovered large interfacial spin-relaxatio n rates for V/Cu, Nb/Cu, and W/Cu interfaces. These rates seem to be unders tandable as due to spin-orbit coupling in high resistivity interfacial allo ys.