Superconducting spin-valve effect and triplet superconductivity inCoOx/Fe1/Cu/Fe2/Cu/Pbmultilayer

Abstract

We report magnetic and superconducting properties of the modified spin valve system CoOx/Fe1/Cu/Fe2/Cu/Pb. Introduction of a Cu interlayer between Fe2 and Pb layers prevents material interdiffusion process, increases the Fe2/Pb interface transparency, stabilizes and enhances properties of the system. This allowed us to perform a comprehensive study of such heterostructures and to present theoretical description of the superconducting spin valve effect and of the manifestation of the long-range triplet component of the superconducting condensate.

Reentrance phenomenon in superconductor/ferromagnet nanostructures and their application in superconducting spin valves for superconducting electronics

“…Indeed, recent calculations have shown [42] that not only the "direct switching" ( ) [42], which can be most spectacularly detected as a reentrant behavior of superconductivity as a function of the angle between magnetic moments of the F1 and F2 ferromagnetic layers. It has been shown that superconducting T c for the F1/N/F2/S structure, calculated with physical parameters derived from the experiments described above, keeps all features predicted in [42] for the simplified model, and the triplet component was detected in F1/N/F2/S multilayer structure [44][45][46][47][48] opening the perspectives for the triplet spin-valve design for superconducting electronics [49,50]. One can see that the functionality of the superconductor/ferromagnet layered nanostructures can be successfully utilized to build a novel base elements for superconducting electronics development.…”

“…According to Ref. 20, l F ≈ 4.4 nm for a Cu 47 Ni 53 alloy with resistivity ρ F = 57 μΩ·cm (bulk material, T = 10 K). Assuming that the product 〈ρ F l F 〉 ≈ 2.5·10 -5 μΩ·cm 2 remains unchanged upon adding impurities [21] one gets l F ~ 10 nm for our Cu 41 Ni 59 alloy using the data for the low-temperature resistivity from Ref.…”

Isolation of proximity-induced triplet pairing channel in a superconductor/ferromagnet spin valve

“…For the CoO x /Fe1/Cu/Fe2/Cu/Pb structure, the superconducting spin-valve effect ∆T c vanishes in the range of thicknesses d Fe2 ≈0.8-1.0 nm [17,20]. From the analysis of the data on the dependence T c (d Py ), it was concluded that the depth of penetration of the Cooper pairs into the permalloy layer is two times greater than the value obtained for iron.…”

“…In all previous studies of our group (see [10,[17][18][19][20]), the experimental data on the critical temperature T c were compared with the parameter of the theory W, which determines the degree of suppression of superconductivity by the ferromagnetic layer (see [7]). The effective boundary condition for the real component of the anomalous Green's function can be written as…”

“…Here, for the first time, we carried out a direct comparative analysis of the theoretically calculated and experimentally measured values of the superconducting transition temperature T c . For the theoretical calculation of the dependence T c (α), we used the theory proposed by Fominov and his colleagues (see [9]) for the case of an arbitrary transparency of the F2/S interface (see [17,20]). The result of this calculation is represented by the solid line in Fig.…”