Reentrance of the induced diamagnetism in gold-niobium proximity cylinders

We discuss the magnetic response of gold-niobium proximity cylinders in the temperature range 100 \mu K<T<9 K. The temperature dependence of the susceptibility in the diamagnetic regime is described well by the quasiclassical Eilenberger theory including an elastic mean-free path l. In the mesoscopic regime, the temperature dependence of the reentrant paramagnetic susceptibility \chi_para(T) \propto \exp[-L/3\xi^d_N(T)] is governed by the dirty limit coherence length \xi^d_N(T)=\sqrt{1/3\xi_N l_N}, with \xi_N the clean limit coherence length obtained from breakdown field measurements and l_N the measured mean-free path in the gold layer. At T=100 \mu K, \chi_para compensates about 1/5 of the induced diamagnetic susceptibility in gold.