Superconducting Spin Valve Effect in a Co/Pb/Co Heterostructure with Insulating Spacers

The superconducting properties of a Co/Pb/Co heterostructure with thin insulating spacers, which are oxidized superconductor/ferromagnet interfaces, have been studied. The behavior of the critical transition temperature T_c of the heterostructure to a superconducting state at a change in the relative orientation of the magnetizations of the ferromagnetic layers from antiparallel to parallel (the so-called superconducting spin valve effect) has been examined. This effect is usually most pronounced in the case of a perfect metal contact at superconductor/ferromagnet interfaces. In this work, a significant superconducting spin valve effect is observed in structures with worsened superconductor/ferromagnet interfaces. A change in the relative orientation of the magnetizations of two ferromagnetic Co layers from antiparallel to parallel leads to the change in T_c by 0.2 K at the optimal thickness of the superconducting Pb layer. Our studies verify the still unconfirmed results obtained in [G. Deutscher and F. Meunier, Phys. Rev. Lett. 22, 395 (1969)] and open new interesting possibilities for improving the parameters of the superconducting spin valve.