Physical properties of the superconducting spin-valve Fe/Cu/Fe/In heterostructure

We report on structural, magnetic, and superconducting properties of the spin-valve multilayer system CoO sub(x)/Fe1/Cu/Fe2/In. For most of the thicknesses of the second iron layer d sub(Fe2) up to 2 nm, we have observed a full spin-valve effect for the superconducting current, i.e., a complete transition from the normal to the superconducting state by changing the mutual orientation of the magnetizations of the Fe1 and Fe2 layers. For d sub(Fe2) < 1 nm, the superconducting transition temperature T super(P) sub(c) for the parallel orientation of magnetizations of the Fe1 and Fe2 layers is smaller than that for the antiparallel orientation T super(AP) sub(c), which corresponds to the direct spin-valve effect. For d sub(Fe2) [> or =, slanted] 1 nm, we have found the inverse spin-valve effect with Delta T sub(c) = T super(AP) sub(c) - T super(P) sub(c) < 0. Further, in samples with a fixed thickness of the In layer, we have observed an oscillating dependence of its superconducting transition temperature T sub(c) on d sub(Fe2). The analysis of the T sub(c)(d sub(Fe2)) dependence using the theory of the superconducting-ferromagnetic proximity effect has enabled determination of all microscopic parameters of the studied system. With these parameters, a satisfactory description of the sign-changing oscillating behavior of the spin-valve effect Delta T sub(c)(d sub(Fe2)) has been obtained using a recent theory by Fominov et al. [Ya. V. Fominov et al., Pis'ma Zh. Eksp. Teor. Fiz. 91, 329 (2010) [JETP Lett. 91, 308 (2010) (http://dx.doi.org/10.1134/S002136401006010X)]].