WEAK-LOCALIZATION-LIKE EFFECTS IN SUPERCONDUCTOR-FERROMAGNET-SUPERCONDUCTOR STRUCTURES

We report measurements of the resistance as a function of temperature and magnetic field in structures containing a narrow (similar to 2 mu m) ferromagnetic strip connecting two superconducting films. The low-f ield magnetoresistance has a general appearance similar to that expect ed for weak localization, but the magnitude is much too large to be ac counted for in terms of this mechanism. In zero field the resistance e xhibits behaviour well below the critical temperature of the supercond uctor which cannot be attributed to the usual proximity effect. Certai n features of the results suggest that this behaviour may be associate d with electron phase coherence.