Diverging giant magnetoresistance in ferromagnet-superconductor-ferromagnet trilayers

Abstract

The relevance of pair-breaking by exchange and dipolar fields, and by\ninjected spins in a low carrier density cuprate\nY$_{1-x}$Pr$_x$Ba$_2$Cu$_3$O$_7$ sandwiched between two ferromagnetic La$_{2 /\n3}$Sr$_{1 / 3}$MnO$_{3}$ layers is examined. At low external field ($H_{ext}$),\nthe system shows a giant magnetoresistance(MR), which diverges deep in the\nsuperconducting state. We establish a distinct dipolar contribution to MR near\nthe switching field(H$_c$) of the magnetic layers. At H$_{ext} \\gg$ H$_c$, a\nlarge positive MR, resulting primarily from the motion of Josephson vortices\nand pair breaking by the in-plane field, is seen.\n