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arXiv · 1911.10168

Proximity effect in [Nb(1.5nm)/Fe(x)]$_{10}$/Nb(50nm) superconducting/ferromagnet heterostructures

Yu. N. Khaydukov·S. Pütter·L. Guasco·R. Morari·G. Kim·T. Keller·A. S. Sidorenko·B. Keimer
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Abstract

We have investigated the structural, magnetic and superconducting properties of [Nb(1.5nm)/Fe(x)]$_{10}$ superlattices deposited on a thick Nb(50nm) layer. Our investigation showed that the Nb(50nm) layer grows epitaxially at 800$^\circ$C on Al$_2$O$_3$(1$\bar{1}$02) substrate. Samples grown at this condition posses 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 properties of a weak ferromagnet. Proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by co-existing superconducting and normal-state domains. 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 periodic Fe/Nb structure.

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Yu. N. Khaydukov, S. Pütter, L. Guasco, R. Morari, G. Kim, T. Keller, A. S. Sidorenko, B. Keimer. 2019-11-22. Proximity effect in [Nb(1.5nm)/Fe(x)]$_{10}$/Nb(50nm) superconducting/ferromagnet heterostructures. https://doi.org/10.3762/bjnano.11.109

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