VORTEX AND NONVORTEX NUCLEATION OF SUPERCONDUCTIVITY IN FERROMAGNETIC-SUPERCONDUCTING-FERROMAGNETIC TRIPLE LAYERS

Superconducting nucleation fields for ferromagnetic-superconducting-ferromagnetic (M/S/M) triple layers are calculated when the magnetic field is applied parallel to the SIM interfaces, the S layer is of arbitrary thickness d, and the M metals are identical and very thick. Both vortex and nonvortex nucleation are considered and the thickness d(cr) at which the vortices start to nucleate is determined. Since the superconductivity is significantly suppressed near the S IM interfaces, the thickness d(cr) substantially increases with respect to the case of a single S film.