Ferromagnetic 0π Junctions as Classical Spins

M. L. Della Rocca, M. Aprili, T. Kontos, A. Gomez, and P. Spathis
Phys. Rev. Lett. 94, 197003 – Published 17 May 2005

Abstract

The ground state of highly damped PdNi based 0π ferromagnetic Josephson junctions shows a spontaneous half quantum vortex, sustained by a supercurrent of undetermined sign. This supercurrent flows in the electrode of a Josephson junction used as a detector and produces a ϕ0/4 shift in its magnetic diffraction pattern. We have measured the statistics of the positive or the negative sign shift occurring at the superconducting transition of such a junction. The randomness of the shift sign, the reproducibility of its magnitude, and the possibility of achieving exact flux compensation upon field cooling are the features which show that 0π junctions behave as classical spins, just as magnetic nanoparticles with uniaxial anisotropy.

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  • Received 19 January 2005

DOI:https://doi.org/10.1103/PhysRevLett.94.197003

©2005 American Physical Society

Authors & Affiliations

M. L. Della Rocca1,2,*, M. Aprili1,3, T. Kontos4, A. Gomez1, and P. Spathis1

  • 1Ecole Supèrieure de Physique et Chimie Industrielles (ESPCI), 10 rue Vauquelin, 75005 Paris, France
  • 2Dipartimento di Fisica “E. R. Caianiello,” Università degli Studi di Salerno, via S. Allende, 84081 Baronissi (Salerno), Italy
  • 3CSNSM-CNRS, Bâtiment 108, Université Paris-Sud, 91405 Orsay, France
  • 4Institute of Physics, University of Basel, Klingelbergstrasse, 82, CH-4056 Basel, Switzerland

  • *Electronic address: marilu@sa.infn.it

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Vol. 94, Iss. 19 — 20 May 2005

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