Changes in resistance, stress and microstructure during annealing were studied in Ni-20wt%Fe(100nm)/Cu(200nm)/NiFe(100nm) layers. Irreversible resistance changes and concentration-depth profiles showed that at, and above, 200C diffusion of Ni into Cu as well as that of Cu into Ni-Fe occurred. Grain-boundary diffusion was the expected interdiffusion mechanism between 200 and 300C. Lattice diffusion already predominated by about 400C. This was confirmed by estimates of the diffusion length; obtained by using diffusion coefficients which were based upon Cu/Ni multi-layers. For a given annealing time (2h), the diffusion lengths were equal to 10nm for grain-boundary diffusion and to 0.4nm for lattice diffusion at 200C. The values at 300C were 400 and 4nm, respectively.

Interdiffusion in NiFe/Cu/NiFe Trilayers - Possible Failure Mechanism for Magnetoelectronic Devices. W.Brückner, S.Baunack, M.Hecker, J.I.Mönch, L.Van Loyen, C.M.Schneider: Applied Physics Letters, 2000, 77[3], 358-60