The Superconducting Magnetoresistance Effect in Ni80Fe20–Nb–Ni80Fe20 and Co–Nb–Co Trilayers: Requisites for Tailoring its Magnitude

Abstract

The superconducting magnetoresistance effect (SMRE) observed in trilayers (TLs) consisting of a superconducting (SC) Nb interlayer and two outer ferromagnetic (FM) Ni80Fe20 and Co layers is studied. We observed that the SMRE exhibits a pronounced magnitude (R max−R min)/R nor of order 45 % and 86 % for the NiFe-based and Co-based TLs, respectively. For the NiFe-based TLs, the dynamic transport behavior of the observed SMRE is presented through detailed I–V characteristics that exhibit a nonlinear character even extremely close to the critical temperature, $T_{c}^{\mathrm{SC}}$ . Also, the detailed evolution of the longitudinal and transverse components of the TL magnetization from close to well below $T_{c}^{\mathrm{SC}}$ is presented. For the Co-based TLs, the obtained magnetization and transport data justify that a strict requisite for the observation of a pronounced SMRE across $T_{c}^{\mathrm{SC}}$ is that the coercivities of the FM layers should be similar. The combined data on the NiFe-based and Co-based TLs show that across the superconducting transition the SMRE is influenced by out-of-plane stray-fields, attaining pronounced values when the respective coercive fields coincide, thus enabling the transverse magnetic coupling of the outer FM layers through the SC interlayer.