Switchable collective pinning of flux quanta using magnetic vortex arrays: Experiments on square arrays of Co dots on thin superconducting films

We constructed a superconducting/ferromagnetic hybrid system in which the ordering of the pinning potential landscape for flux quanta can be manipulated. Flux pinning is induced by an array of magnetic nanodots in the ``magnetic vortex'' state and is controlled by the magnetic history. This allows switching on and off the collective pinning of the flux lattice. In addition, we observed field-induced superconductivity that originates from the annihilation of flux quanta induced by the stray fields from the magnetic vortices.