We have observed a nonmonotonic behavior of the superconducting critical temperature $T_c$ versus the CuMn layer thickness in multilayers of Nb/CuMn with fixed Nb layer thickness (∼250 Å). The results have been interpreted assuming the presence of the $\pi$ phase in the case of layered superconducting systems with weak magnetic coupling, where the phase $\phi$ of the superconducting order parameter can vary in the range $0<\mathrm{}\phi <\pi$ between adjacent superconducting layers.

• Received 22 September 1995

DOI:https://doi.org/10.1103/PhysRevB.53.14040