Irreversibility line in Nb/CuMn multilayers with a regular array of antidots

The transport properties of superconducting multilayers with a regular arra y of antidots obtained by electron-beam lithography have been measured at d ifferent temperatures in the presence of external perpendicular magnetic fi elds. Hysteresis in the I-V characteristics was observed, which disappears when approaching the upper critical magnetic field curve H-c2(T). By compar ing these data with other results (Arrhenius plots of resistive transition curves, log V-log I characteristics) we have been able to relate the onset of the hysteresis to the presence of an irreversibility line. We discuss se veral possible mechanisms to clarify the nature of this Line. Among them th e most plausible seems to be Vortex melting mainly induced by quantum fluct uations.