Magnetic tunable confinement of the superconducting condensate in superconductor/ferromagnet hybrids

The effect of a nonuniform magnetic field induced by a ferromagnet on the magnetoresistance of thin-film superconductor/ferromagnet hybrid structures was investigated experimentally. Two different magnetic textures with out-of-plane magnetization were considered: a plain ferromagnetic film with bubble domains and a regular array of ferromagnetic dots. The stray fields of the structures are able to affect the spatial profile of the superconducting condensate, leading to a modification of the dependence of the critical temperature Tc on an external magnetic field H. We showed how the standard linear Tc(H) dependence with a single maximum at H=0 can be continuously transformed into so-called reentrant phase boundary with two Tc peaks. We demonstrated that both domain-wall superconductivity and field-induced superconductivity are different manifestations of the magnetic confinement effect in various magnetic patterns.