Influence of the FFLO-like state on the upper critical field of a superconductor/ferromagnet bilayer: Angular and temperature dependence

D. Lenk, M. Hemmida, R. Morari, V. I. Zdravkov, A. Ullrich, C. Müller, A. S. Sidorenko, S. Horn, L. R. Tagirov, A. Loidl, H.-A. Krug von Nidda, and R. Tidecks
Phys. Rev. B 93, 184501 – Published 2 May 2016

Abstract

We investigated the upper critical magnetic field Hc of a superconductor-ferromagnet (S/F) bilayer of Nb/Cu41Ni59 and a Nb film (as reference). We obtained the dependence of Hc and Hc (perpendicular and parallel to the film plane, respectively) on the temperature T by measurements of the resistive transitions and the dependence on the inclination angle θ of the applied field to the film plane, by nonresonant microwave absorption. Over a wide range, Hc and Hc show the temperature dependence predicted by the Ginzburg-Landau theory. At low temperatures and close to the critical temperature, deviations are observed. While Hc(θ) of the Nb film follows the Tinkham prediction for thin superconducting films, the Nb/Cu41Ni59-bilayer data exhibit deviations when θ approaches zero. We attribute this finding to the additional anisotropy induced by the quasi-one-dimensional Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like state and propose a new vortex structure in S/F bilayers, adopting the segmentation approach from high-temperature superconductors.

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  • Received 16 September 2015
  • Revised 31 March 2016

DOI:https://doi.org/10.1103/PhysRevB.93.184501

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

D. Lenk1, M. Hemmida1,2, R. Morari1,3,4, V. I. Zdravkov1,3,*, A. Ullrich1, C. Müller1, A. S. Sidorenko3, S. Horn1, L. R. Tagirov1,4, A. Loidl2, H.-A. Krug von Nidda2, and R. Tidecks1

  • 1Experimentalphysik II, Institut für Physik, Universität Augsburg, Universitätsstraße 1, D-86159 Augsburg, Germany
  • 2Experimentalphysik V, Center for Electronic Correlations and Magnetism, Institut für Physik, Universität Augsburg, Universitätsstraße 1, D-86159 Augsburg, Germany
  • 3D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Academiei Str. 3/3, MD2028 Kishinev, Moldova
  • 4Solid State Physics Department, Kazan Federal University, Kremlevskaya Str. 18, 420008 Kazan, Russian Federation

  • *Present Address: Institute of Applied Physics and Interdisciplinary Nanoscience Center, Universität Hamburg, Jungiusstraße 9A, D-20355 Hamburg, Germany.

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Vol. 93, Iss. 18 — 1 May 2016

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