Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 25: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 25.4: Vortrag

Mittwoch, 27. Februar 2008, 14:45–15:00, H 3010

Superconducting spin valve structures grown on epitaxial [Fe/V]-(001) superlattices — •Gregor Nowak¹, Hartmut Zabel¹, Björgvin Hjörvarsson², and Kurt Westerholt¹ — ¹Experimentalphysik /Festkörperphysik, Ruhr - Universität Bochum, Germany — ²Department of Physics, University of Uppsala, Sweden

In a superconducting F1/S/F2 spin valve trilayer structure a superconducting layer (S) is imbedded by a ferromagnetic layer F1 and F2. Model calculations based on the F/S proximity effect have shown that with suitable parameters for the thicknesses and correlations lengths of the F and S-layers the superconductivity can be switched off and on by rotating the magnetization of F1 and F2 from a parallel to an antiparallel orientation. Experimentally, however, it turned out to be challenging to optimize the F1/S/F2 device and until now only very small differences of the superconducting (SC) transition temperature Ts between the parallel and antiparallel orientation has been observed. We have prepared epitaxial F1/S/F2 spin valve systems using an [Fe/V] superlattice as F1, V as the superconducting layer S and Co, Fe(1-x)V(x) layer as F2. The epitaxial quality in this kind of heterostructures reduces the impurity and surface electron scattering so that the superconducting coherence length approaches the thickness of the V-layer. We observe a well pronounced spin valve effect, especially in the system with the Fe(1-x)V(x)-alloy layers, which can be as high as tens of mK.