The spin valve effect for the superconducting current based on the superconductor/ferromagnet proximity effect has been studied for a CoO_x/Fe1/Cu/Fe2/Cu/Pb multilayer. The magnitude of the effect $\Delta T_c$ = T_c^{ AP} - T_c^{ P}, where T_c^{ P} and T_c^{ AP} are the superconducting transition temperatures for the parallel (P) and antiparallel (AP) orientation of magnetizations, respectively, has been measured for different thicknesses of the Fe1 layer d_{ Fe1}. The obtained dependence of the effect on d_{ Fe1} reveals that $\Delta T_c$ can be increased in comparison with the case of a half-infinite Fe1 layer considered by the previous theory. A maximum of the spin valve effect occurs at d_{ Fe1} ~ d_{ Fe2}. At the optimal value of d_{ Fe1}, almost full switching from the normal to the superconducting state when changing the mutual orientation of magnetizations of the iron layers Fe1 and Fe2 from P to AP is demonstrated.
Categories: cond-mat.supr-con cond-mat.mes-hall