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

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Abstract
We have made thickness dependent in situresistivity 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, Ni 80 Fe 20 , and Ta,deposited in differing orders to isolate the scattering at interfaces relevant to common spin-valvestructures. 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 Cuinterfaces 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.