Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers

TL;DR

This paper investigates how magnetoresistance and critical temperature in ferromagnet-superconductor multilayers are affected by external magnetic fields, revealing abrupt changes and re-entrant superconductivity in nanoscale spin valve systems.

Contribution

It introduces a detailed study of magnetoresistive effects and critical temperature behavior in Manganite-Cuprate multilayers with variable layer numbers and magnetic field strengths.

Findings

Abrupt changes in critical temperature and magnetoresistance at flipping fields.

Re-entrant superconductivity at high magnetic fields.

Distinct behaviors depending on the number of Cuprate layers.

Abstract

We consider a nanoscale system consisting of Manganite-ferromagnet and Cuprate-superconductor multilayers in a spin valve configuration. The magnetization of the bottom Manganite-ferromagnet is pinned by a Manganite-antiferromagnet. The magnetization of the top Manganite-ferromagnet is coupled to the bottom one via indirect exchange through the superconducting layers. We study the behavior of the critical temperature and the magnetoresistance as a function of an externally applied parallel magnetic field, when the number of Cuprate-superconductor layers are changed. There are two typical behaviors in the case of a few monolayers of the Cuprates: a) For small magnetic fields, the critical temperature and the magnetoresistance change abruptly when the flipping field of the top Manganite-ferromagnet is reached. b) For large magnetic fields, the multilayered system re-enters the zero-resistance (superconducting) state after having become resistive (normal).