Magnetization-controlled transport critical current in ferromagnet/superconductor/ferromagnet trilayers

We have investigated the influence of the ferromagnet magnetization on the transport critical-current density Jc in ferromagnet (Co)/superconductor (Nb)/ferromagnet (Co) trilayers under applied fields parallel to the film surface. Irrespective of field polarity, the pronounced peak of Jc was observed below the lower critical field Hc1, in contrast to usual monotonic decrease of Jc with field. We find that the position of the minimum in Jc appearing around zero field, is dependent on the sweep direction of the applied field. These results can be explained by the pair-breaking that is controlled by the relative alignment between the applied field and the in-plane magnetization of the Co layer. (author)