Unconventional proximity effect and inverse spin-switch behavior in a model manganite-cuprate-manganite trilayer system

TL;DR

This paper theoretically investigates a manganite-cuprate-manganite trilayer system, revealing an unconventional proximity effect and inverse spin-switch behavior driven by strong interfacial magnetic coupling and negative spin polarization.

Contribution

It introduces a model explaining the dominant role of interfacial magnetic coupling over spin injection, leading to novel inverse spin-switch phenomena in the system.

Findings

Interfacial magnetic coupling is stronger than spin injection effects.

Superconducting transition temperature depends strongly on cuprate layer thickness.

Applying a magnetic field can increase the superconducting transition temperature due to negative spin polarization.

Abstract

The proximity effect in a model manganite-cuprate system is investigated theoretically. We consider a situation in which spin-polarized electrons in manganite layers antiferromagnetically couple with electrons in cuprate layers as observed experimentally. The effect of the interfacial magnetic coupling is found to be much stronger than the injection of spin-polarized electrons into the cuprate region. As a result, the superconducting transition temperature depends on the thickness of the cuprate layer significantly. Since the magnetic coupling creates {\em negative} spin polarization, an applied magnetic field and the negative polarization compete resulting in the inverse spin-switch behavior where the superconducting transition temperature is increased by applying a magnetic field.