SCALING OF TC IN PROXIMITY-COUPLED SUPERCONDUCTING NORMAL-METAL MULTILAYERS

The superconducting transition temperature T(c) has been measured in the multilayered system Nb/CuX, where CuX represents Cu, Cu1-yMny, or Cu0.95Ge0.05. The advantage of this system is that the superconductor layer thickness, normal-metal layer thickness, normal-metal magnetic concentration, and normal-metal bulk resistivity can be independently varied. Our data show that the variation of T(c) with changing superconductor-layer thickness d(s) exhibits scaling consistent with the equation (T(c)b-T(c))/T(c)b = (d(s)/d0)-P, where d0 is a fitting parameter and T(c)(b) is T(c) for bulk Nb. We find the exponent p to increase systematically with increasing normal-metal layer thickness, and magnetic impurity concentration, with 1 less-than-or-equal-to p < 2, consistent with the limiting forms of two theoretical models.