Diverging giant magnetoresistance in ferromagnet-superconductor-ferromagnet trilayers

Abstract

The relevance of pair-breaking by exchange and dipolar fields, and by injected spins in a low carrier density cuprate Y;_1-xPr_xBa₂Cu₃O₇ sandwiched between two ferromagnetic La_2/3Sr_1/3MnO₃ 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_extH_c, a large positive MR, resulting primarily from the motion of Josephson vortices and pair breaking by the in-plane field, is seen.