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TT: Fachverband Tiefe Temperaturen
TT 21: Superconductivity: Poster Session
TT 21.37: Poster
Montag, 16. März 2015, 15:00–18:00, Poster B
Upper Critical Field and Vortices in S/F Bilayers Exhibiting the Quasi-Onedimensional FFLO-like State — Daniel Lenk1, •Mamoun Hemmida1, Jan Kehrle1, Vladimir I. Zdravkov1,2, Aladin Ullrich1, Günther Obermeier1, Roman Morari1,3, Claus Müller1, Anatolie S. Sidorenko3, Alois Loidl1, Hans-Albrecht Krug von Nidda1, Lenar Tagirov1,4, Siegfried Horn1, and Reinhard Tidecks1 — 1Institut für Physik, Universität Augsburg, D-86159 Augsburg, Germany — 2Present address: Institut für angewandte Physik, Universität Hamburg, D-20355 Hamburg, Germany — 3D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, MD 2028 Kishinev, Moldova — 4Solid State Physics Department, Kazan Federal University, 420008 Kazan, Russia
We investigate the temperature dependence of the upper critical field, Bc2, in superconductor/ferromagnet (S/F) bilayers as a function of the F-layer thickness, dF, by resistance measurements. We extracted GL coherence lengths and estimated an effective thickness of the superconducting layer by evaluating the perpendicular coherence length at the 3D-2D crossover temperature in the parallel Bc2. We found an unexpected non-monotonous behavior of the effective thickness as a function of dF. Moreover, we investigated the anisotropy of Bc2 by microwave absorption. The results show a deviation from Tinkham’s prediction for thin films, which we attribute to the additional anisotropy induced by the quasi-1D FFLO-like state. Thus, we propose a new type of vortex, developing in the S/F bilayer in magnetic fields applied close to parallel. This work was supported by DFG Grant No. HO955/9-1.