Proximity effect in [Nb(1.5 nm)/Fe(x)]₁₀/Nb(50 nm) superconductor/ferromagnet heterostructures

Abstract

We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe(x)]10 superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al2O3(1−102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15–20. By using neutron reflectometry we show that Fe/Nb superlattices with x < 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to x = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure.

Tuning Epitaxial Growth of Nb on MgO(100)

“…The transport properties of the thin Nb layers were studied with a 4‐probe technique. [ 29 ] An ac current with amplitude 100 µA was applied in plane. The residual resistivity ratio was defined as RRR = (295 K) / (10 K), and the superconducting transition temperature T C was defined as the midpoint between the start and end of transition Δ T C .…”

Density of states in the presence of spin-dependent scattering in SF bilayers: a numerical and analytical approach

“…The resulting system must be complemented by the boundary conditions at the outer boundary of a ferromagnet, (5) and the Kupriyanov-Lukichev boundary conditions at the FS interface [83], (6) (7) Here γ = ξ s σ n /ξ f σ s , σ s is the conductivity of the S layer, and ξ s = is the superconducting coherence length. The indices of the θ-parameterized Green's functions are omitted, since there is no mixing between the components θ ↑ and θ ↓ .…”

“…It is well-known that superconductivity can be induced in a nonsuperconducting metal in hybrid structures due to the proximity effect [1][2][3][4][5][6][7]. For instance, in NS bilayers (where N denotes a normal metal and S denotes a superconductor), the superconducting correlations penetrate into the normal metal layer over a characteristic decay length ξ n = where D n is the diffusion constant in the normal metal and T c is the transition temperature.…”

Density of states in the presence of spin dependent scattering: numerical and analytical approach

“…It is well-known that superconductivity can be induced into a non-superconducting metal in the hybrid structures due to the proximity effect [1][2][3][4][5][6][7]. For instance, in NS bilayers (where N denotes a normal metal and S -a superconductor) the superconducting correlations penetrate into the normal metal layer over a characteristic decay length 𝜉 𝑛 .…”