Flux pinning characteristics have been investigated for superconductor(S)/s
uperconductor(S') NbTi/Nb multilayers. The maximum of the perpendicular pin
ning force (F-p perpendicular to max) as a function of the structure modula
tion length Lambda has a peak in the quasi-two-dimensional superconductivit
y region. The large perpendicular pinning force observed in the S/S' multil
ayer is caused by Nb layers, which act as the repulsive pinning centers. (C
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