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-field magnetoresistance has a general appearance similar to that expected for weak localization, but the magnitude is much too large to be accounted for in terms of this mechanism. In zero field the resistance exhibits behaviour well below the critical temperature of the superconductor which cannot be attributed to the usual proximity effect. Certain features of the results suggest that this behaviour may be associated with electron phase coherence.