We report the observation of the 0-π junction state in superconductor-ferromagnet-superconductor Josephson junctions arising from variations in the effective barrier thickness d ξF. By varying the temperature, the junctions can be tuned from the 0- to the π -state through an intermediate regime in which parts of the junction are in each state. A signature of the 0-π regime is that the usual peak in the critical current diffraction pattern at zero magnetic field becomes a dip, evidence for sign changes in the critical current density. In some junctions, the zero-field critical current does not vanish at any temperature and half-integer Shapiro steps are observed, indicating the presence of spontaneous supercurrents circulating within the junctions around the 0-π interfaces.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jul 24 2006|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics