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.