Superconducting spin-valve effect in heterostructures with ferromagnetic Heusler alloy layers

Abstract

We report a comparative analysis and theoretical description of the superconducting properties of two spin-valve-valve structures containing the Heusler alloy Co${}_2$Cr${}_{1-x}$Fe${}_x$Al${}_y$ as one of two ferromagnetic (F1 or F2) layers of the F1/F2/S structure, where S stands for the superconducting Pb layer. In our experiments we used the Heusler alloy layer in two roles: as a weak ferromagnet on the place of the F2 layer and as a half-metal on the place of the F1 layer. In the first case, we obtained a large ordinary superconducting spin-valve effect $\Delta T_c$ assisted by the triplet superconducting spin-valve effect $\Delta T_c^{trip}$. In the second case, we observed a giant magnitude of $\Delta T_c^{trip}$ reaching 0.5 K. An underlying theory based on the solution of the Usadel equations using Kupriyanov-Lukichev boundary conditions with arbitrary material parameters for all layers and arbitrary boundary parameters for all interfaces is presented in Appendix. We find a good agreement between our experimental data and theoretical results.

13 pages, 7 figures

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