Specular and diffuse electron scattering at interfaces in metal spin-valve structures

We have made thickness dependent in situ resistivity measurements on sputtered metal films in real time during film deposition. These measurements allow the separation of the bulk and finite-size contributions to the resistance. The metals studied were Co, Cu, Ni80Fe20, and Ta, deposited in differing orders to isolate the scattering at interfaces relevant to common spin-valve structures. We see sources of excess diffuse scattering in bilayers of Ta with the 3d metals, regardless of the deposition order. We see a similar effect for Co on Cu, but not for Cu on Co. In some cases, we see significant changes in film resistance from overlayers as thin as 2 Å. These results show that the two Cu interfaces in a spin valve are not equivalent, and that other interfaces in the structure may be important. We discuss the origin of the diffuse scattering in terms of interdiffusion or a roughening transition during the initial deposition and island coalescence.