CALCULATION OF THE UPPER CRITICAL FIELDS IN NB TA MULTILAYERS/

The Takahashi-Tachiki proximity-effect theory is applied to the Nb/Ta multilayer system. The diffusion coefficients of the two metals and th e critical temperature of Nb are used as free parameters in fitting ex perimental phase diagrams. Magnetic-coherence-length scaling is used i n 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 realisti c result.