Imprinting properties of magnetic vortices into superconducting films.

We investigated experimentally the magnetotransport properties of superconducting Al thin films on top of sub-100 nm Fe nanodot arrays. Samples with arrays of single-domain magnetic dots behave similar to plain Al films. A dramatically different behavior is observed for arrays of dots in the so-called magnetic vortex-state. For these, the details of the magnetic reversal are ``imprinted'' into the superconductor and show up in the magnetotransport properties below the superconducting T$_{C}$. The resulting hybrid system shows a giant (up to 10$^{5}$ {\%}) hysteretic magnetoresistance with different reversible/irreversible regimes related to the array's magnetic state. Such controllable effects originate from the stray fields produced by the magnetic vortex cores in the nanodots, which induce a normal/superconducting transition depending on the distribution of the vortex cores polarities.