title: Ferromagnetic 0-pi junctions as classical spins.
abstract: The ground state of highly damped PdNi based 0-pi 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 phi(0)/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 0-pi junctions behave as classical spins, just as magnetic nanoparticles with uniaxial anisotropy.
authors.affiliation: Ecole Supèrieure de Physique et Chimie Industrielles (ESPCI), Paris, France. marilu@sa.infn.it
authors.forename: M L
authors.initials: ML
authors.lastname: Della Rocca
authors.forename: M
authors.initials: M
authors.lastname: Aprili
authors.forename: T
authors.initials: T
authors.lastname: Kontos
authors.forename: A
authors.initials: A
authors.lastname: Gomez
authors.forename: P
authors.initials: P
authors.lastname: Spathis