Influence of the FFLO-like State on the Upper Critical Field of a S/F 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; R. Tidecks

doi:10.1103/PhysRevB.93.184501

paper

Influence of the FFLO-like State on the Upper Critical Field of a S/F Bilayer: Angular and Temperature Dependence

arXiv:1604.03361 · doi:10.1103/PhysRevB.93.184501

Abstract

We investigated the upper critical magnetic field, $H_{c}$ , of a superconductor-ferromagnet (S/F) bilayer of Nb/Cu $_{41}$ Ni $_{59}$ and a Nb film (as reference). We obtained the dependence of $H_{c ⊥}$ and $H_{c ∥}$ (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 non-resonant microwave absorption. Over a wide range, $H_{c ⊥}$ and $H_{c ∥}$ show the temperature dependence predicted by the Ginzburg-Landau theory. At low temperatures and close to the critical temperature deviations are observed. While $H_{c} (θ)$ of the Nb film follows the Tinkham prediction for thin superconducting films, the Nb/Cu $_{41}$ Ni $_{59}$ -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.

arXiv commentAccepted to Phys. Rev. B

Influence of the FFLO-like State on the Upper Critical Field of a S/F Bilayer: Angular and Temperature Dependence

Abstract

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