Enhancing current-perpendicular-to-plane magnetoresistance by adding interfaces within ferromagnetic layers

We show that adding “internal interfaces” within each Co layer can enhance both the total current-perpendicular-to-plane specific resistance, AR, and the change in specific resistance with magnetic field, AΔR, of [Py/Cu/Co/Cu]3 hybrid multilayers, AΔR by over 100%, with only a small increase in the total sample thickness. However, the growth of both AR and AΔR with the number of inserted interfaces is slower than predicted by a simple two-current series-resistor model. We provide evidence that this less rapid growth is due to spin-flipping at the Co/Cu interfaces, plus the formation of “incomplete interfaces” when the Cu layers are very thin.