Asymmetric flux pinning by magnetic antidots

We have studied the flux pinning in a type-II superconducting Pb film covering a regular array of magnetic antidots. The magnetic antidots are made by introducing holes in a Co/Pt multilayer with perpendicular anisotropy. The magnetization curves of the resulting hybrid system are extremely asymmetric with respect to the field polarity, proving that a magnetic contribution dominates the pinning potential.