Abstract
The ground state of highly damped PdNi based 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 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 junctions behave as classical spins, just as magnetic nanoparticles with uniaxial anisotropy.
- Received 19 January 2005
DOI:https://doi.org/10.1103/PhysRevLett.94.197003
©2005 American Physical Society