It was noted that, in diffusion-driven degradation, it would be possible to predict lifetimes on the basis of a maximum allowed reduction in ΔR/R; where R was the resistivity. Initial results for a CoFe/Cu interface were reported here. Interdiffusion in (111)-textured polycrystalline CoFe/Cu multi-layers was measured and quantified by using X-ray reflectometry. Bulk diffusion predominated above about 540C, and could be described by:

D (m2/s) = 2.92 x 10-8 exp[-2.41(eV)/kT]

Below 540C, grain boundary diffusion predominated and could be described by:

D (m2/s) = 1.91 x 10-17 exp[-0.90(eV)/kT]

Before stabilization of the diffusion process, there was an initial rapid change in the (111) texture. During an initial so-called sharpening of the CoFe/Cu multi-layer interfaces, there was a shortening of the periodicity as well as a decrease in the out-of-plane lattice spacing.

Interdiffusion in CoFe/Cu Multilayers and its Application to Spin-Valve Structures for Data Storage. E.B.Svedberg, K.J.Howard, M.C.Bønsager, B.B.Pant, A.G.Roy, D.E.Laughlin: Journal of Applied Physics, 2003, 94[2], 1001-6