Staircase magnetization anomalies in superconducting Pb/Au bilayer films patterned with antidot lattices

Superconducting Pb( x)/Au(25 nm) bilayers ( x = 50, 100 nm) patterned with antidot lattices exhibit various matching field anomalies depending on experimental conditions. Magnetization peaks at applied fields H = n[20 Oe] ( n = integer) resemble superconducting wire network data; cusps are also observed, consistent with predictions of “giant” vortices in low-kappa films. Sharp “staircase” anomalies spaced by 1–3 Oe are observed in AC magnetization, possibly a result of depinning of intermediate state domains, or macroscopic quantum tunneling between reproducible states of different quantized flux.