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TT: Fachverband Tiefe Temperaturen

TT 28: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 28.7: Vortrag

Mittwoch, 25. März 2009, 17:15–17:30, HSZ 105

Superconducting spin valves based on epitaxial [Fe/V]-superlattices — •Gregor Nowak¹, Moreno Marcellini², Hartmut Zabel¹, Björgvin Hjörvarsson², and Kurt Westerholt¹ — ¹Experimentalphysik/Festkörperphysik, Ruhr Universität Bochum — ²Department of Physics, University of Uppsala, Sweden

In superconducting spin valves of the type S/F1/N/F2 or F1/S/F2 with a superconducting layer S, two ferromagnetic layers F1 and F2 and a normal metallic layer N, the superconducting transition temperature T_S depends on the relative magnetization direction of the ferromagnetic layers F1 and F2. The difference of the transition temperature ΔT_S=T_S^AP-T_S^P with the magnetization direction of F1 and F2 either antiparallel or parallel is called the superconducting spin valve effect [1]. We observed a superconducting spin valve shift of up to ΔT_S=200 mK when aligning the sublattice magnetization in an external magnetic field in S/F1/N/F2 type of spin valves. In the F1/S/F2-type spin valves the ferromagnetic layer F1 was either a [Fe/V] or a [Fe_xV_1−x/V] superlattice, the F2 layer was a Fe-, a Co- or a Fe_xV_1−x film. Using weakly ferromagnetic Fe_xV_1−x alloy layers as F1 and F2 we find a spin valve effect of up to ΔT_S=24 mK. We also present experimental evidence for a drastic reduction or even a sign reversal of the superconducting spin valve effect in the presence of perpendicular magnetic stray fields from ferromagnetic domain walls.

[1] J.Y. Gu, C.-Y. You, J. S. Jiang, J. Pearson, Ya. B. Bazaliy, and S. D. Bader, Phys. Rev. Lett. 89, 267001 (2002)