Diverging giant magnetoresistance in ferromagnet-superconductor-ferromagnet trilayers

The relevance of pair-breaking by exchange and dipolar fields, and by injected spins in a low carrier density cuprate Y1-xPrxBa2Cu3O7 sandwiched between two ferromagnetic La2/3Sr1/3MnO3 layers is examined. At low external field (H-ext), the system shows a giant magnetoresistance (GMR), which diverges deep in the superconducting state. We establish a distinct dipolar contribution to magnetoresistance (MR) near the switching field (H-c) of the magnetic layers. At H-ext >> H-c, a large positive MR, resulting primarily from the motion of Josephson vortices and pair breaking by the in-plane field, is seen.