Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 26: Superconductivity - Heterostructures, Andreev Scattering, Proximity Effect, Coexistence
TT 26.4: Vortrag
Dienstag, 8. März 2005, 11:00–11:15, TU H3027
Diamagnetic screening in Nb/Ag double layers in contact with a ferromagnet — •H. Stalzer1, A. Cosceev1, C. Sürgers1, and H. v. Löhneysen1,2 — 1Physikalisches Institut and DFG Center for Functional Nanostructures (CFN), Universität Karlsruhe, D-76128 Karlsruhe — 2Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe
The magnetization M(T,B) of planar superconducting Nb/Ag and Nb/Ag/Fe heterostructures (thicknesses dNb = 200 nm, dAg = 35 - 800 nm, and dFe = 40 nm) epitaxially grown on sapphire (1120) is studied in parallel magnetic fields B between temperatures of T = 0.06 - 10 K. Below the superconducting phase transition of Nb a further diamagnetic signal occurs at a temperature T⋆ due to screening currents in Ag induced by the proximity effect. In contact with an additional Fe layer the proximity effect vanishes for thick Ag layers (dAg≥ 200 nm). Surprisingly the diamagnetic transition at T⋆ reappears in Nb/Ag/Fe triple layers with a thickness of 20 - 35 nm. Furthermore, we investigate the effect of an additional SiO2 spacer layer of thickness dSiO2 = 1 - 5 nm, separating the Ag and Fe film, on the diamagnetic phase diagram. We propose the realization of a tunable π-contact using weak ferromagnets.