nucleation of superconductivity; superconductor/ferromagnet hybrid; domain-wall superconductivity; field-induced superconductivity
Abstract :
[en] 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 T-c on an external magnetic field H. We showed how the standard linear T-c(H) dependence with a single maximum at H = 0 can be continuously transformed into so-called reentrant phase boundary with two T-c peaks. We demonstrated that both domain-wall superconductivity and field-induced superconductivity are different manifestations of the magnetic confinement effect in various magnetic patterns. (C) 2008 Elsevier B.V. All rights reserved.
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For a large-area superconductors in an uniform magnetic field the ℓ parameter coincides with the magnetic length LH = sqrt(Φ0 / 2 π {divides} H {divides}) (here Φ0 is the flux quantum), what results in the standard expression for the upper critical field: (1 - Tc / Tc 0) = 2 π ξ02 {divides} H {divides} / Φ0.
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