title: 0-pi Josephson tunnel junctions with ferromagnetic barrier.
abstract: We fabricated high quality Nb/Al2O3/Ni(0.6)Cu(0.4)/Nb superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions. Using a ferromagnetic layer with a steplike thickness, we obtain a 0-pi junction, with equal lengths and critical currents of 0 and pi parts. The ground state of our 330 microm (1.3lambda(J)) long junction corresponds to a spontaneous vortex of supercurrent pinned at the 0-pi step and carrying approximately 6.7% of the magnetic flux quantum Phi(0). The dependence of the critical current on the applied magnetic field shows a clear minimum in the vicinity of zero field.
authors.affiliation: Center of Nanoelectronic Systems for Information Technology (CNI), Research Centre Jülich, D-52425 Jülich, Germany. m.weides@fz-juelich.de
authors.forename: M
authors.initials: M
authors.lastname: Weides
authors.forename: M
authors.initials: M
authors.lastname: Kemmler
authors.forename: H
authors.initials: H
authors.lastname: Kohlstedt
authors.forename: R
authors.initials: R
authors.lastname: Waser
authors.forename: D
authors.initials: D
authors.lastname: Koelle
authors.forename: R
authors.initials: R
authors.lastname: Kleiner
authors.forename: E
authors.initials: E
authors.lastname: Goldobin