Diverging Giant Magnetoresistance in the Limit of Infinitely Conducting Spacer

TL;DR

This paper investigates the giant magnetoresistance behavior in a layered cuprate superconductor with ferromagnetic layers, revealing divergence in MR deep in the superconducting state and identifying different mechanisms contributing to MR.

Contribution

It demonstrates the divergence of giant magnetoresistance in the limit of an infinitely conducting spacer and distinguishes dipolar and vortex-related contributions.

Findings

Giant MR diverges deep in the superconducting state.

Dipolar contribution to MR is significant near the magnetic switching field.

Large positive MR at high fields is due to Josephson vortex motion and pair breaking.

Abstract

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