The enhancement of vortex pinning in ferromagnet/superconductor bilayers

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Abstract

The magnetic-domain induced vortex pinning is studied in the ferromagnet/superconductor bilayers (FSB's), in which the F layers are Co/Pt multilayers with perpendicular magnetic anisotropy, and the S layers are either niobium or high temperature superconductor YBa2Cu3O7 (YBCO). The magnetization measurements reveal the enhancement of the flux pinning in both types of FSB's during the reversal of the magnetization of the F layer, but the details of the behavior depend on the type of the S layer. In the case of niobium FSB the maximum of pinning appears when the F layer is in the final stage of the magnetic reversal process, while the FSB with YBCOshows the maximumwhen the F layer is saturated. The possible origins of these differences are discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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