Low-field transport measurements in superconducting Co/Nb/Co trilayers

We report transport measurements in a superconducting Co/Nb/Co trilayer based on elemental ferromagnetic Co and elemental superconducting Nb. The trilayer behaves as a superconducting valve, can be operated at liquid-helium temperature, and can switch from superconductive to normal state in weak applied in-plane magnetic fields. Current-voltage curves, critical currents as a function of temperature and magnetic field, as well as preparation of superconductive or resistive state are addressed here. Data analysis suggests that the superconducting valve behavior can be accounted for by a glassy vortex phase induced in the superconductor by the stray fields from domain walls proliferating around the coercive fields of the ferromagnetic electrodes.