The Takahashi-Tachiki proximity-effect theory is applied to the Nb/Ta multilayer system. The diffusion coefficients of the two metals and the critical temperature of Nb are used as free parameters in fitting experimental phase diagrams. Magnetic-coherence-length scaling is used in order to obtain phase diagrams that best reproduce the measured data. Several parameter sets can compete in fitting an experimental curve. It is not always possible to decide which set gives the most realistic result.
Koperdraad, R. T. W., Wu, H. T., & Lodder, A. (1996). Calcualtion of the upper critical fields in Nb/Ta multilayers. Journal of Physics. Condensed matter, 8, 8787-8797. https://doi.org/10.1088/0953-8984/8/45/014