Unanticipated Proximity Behavior in Ferromagnet-Superconductor Heterostructures with Controlled Magnetic Noncollinearity

L. Y. Zhu, Yaohua Liu, F. S. Bergeret, J. E. Pearson, S. G. E. te Velthuis, S. D. Bader, and J. S. Jiang
Phys. Rev. Lett. 110, 177001 – Published 24 April 2013

Abstract

Magnetization noncollinearity in ferromagnet-superconductor (F/S) heterostructures is expected to enhance the superconducting transition temperature (Tc) according to the domain-wall superconductivity theory, or to suppress Tc when spin-triplet Cooper pairs are explicitly considered. We study the proximity effect in F/S structures where the F layer is a SmCo/Py exchange-spring bilayer and the S layer is Nb. The exchange-spring contains a single, controllable and quantifiable domain wall in the Py layer. We observe an enhancement of superconductivity that is nonmonotonic as the Py domain wall is increasingly twisted via rotating a magnetic field, different from theoretical predictions. We have excluded magnetic fields and vortex motion as the source of the nonmonotonic behavior. This unanticipated proximity behavior suggests that new physics is yet to be captured in the theoretical treatments of F/S systems containing noncollinear magnetization.

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  • Received 28 August 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.177001

© 2013 American Physical Society

Authors & Affiliations

L. Y. Zhu1, Yaohua Liu1, F. S. Bergeret2,3,4, J. E. Pearson1, S. G. E. te Velthuis1, S. D. Bader1,5, and J. S. Jiang1,*

  • 1Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 2Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, E-20018 San Sebastián, Spain
  • 3Donostia International Physics Center (DIPC), Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
  • 4Institut für Physik, Carl von Ossietzky Universität, D-26111 Oldenburg, Germany
  • 5Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA

  • *jiang@anl.gov

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Vol. 110, Iss. 17 — 26 April 2013

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